BEGIN:VCALENDAR VERSION:2.0 PRODID:-//CERN//INDICO//EN BEGIN:VEVENT SUMMARY:A Decade of Near-Infrared Variability in NGC4388: Insights into th e AGN Structure DTSTART;VALUE=DATE-TIME:20230627T153000Z DTEND;VALUE=DATE-TIME:20230627T154500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-893@cern.ch DESCRIPTION:Speakers: Luis Gabriel Dahmer Hahn (Shanghai Astronomical Obse rvatory)\nVariability studies of Active Galactic Nuclei (AGNs) have proven to be a powerful diagnostic tool for understanding the physics and proper ties of these objects. They provide insights into the spatial and temporal distribution of the emitting regions\, the structure and dynamics of the accretion disk\, and the properties of the central black hole. Here\, we p resent the results of a ten-year campaign to monitor the near-infrared emi ssion of the Seyfert 1.9/2 nucleus of NGC4388\, covering J and K band spec troscopy. During this period\, the hot dust continuum of the nucleus of th is object varied by up to 200% under certain wavelength ranges. However\, emission lines of low and medium ionization did not change beyond our erro r margin\, whereas we detected variations of almost 100% at the [Ca$_{\\rm VIII}$] coronal line. These results suggest that between 2011 and 2013\, we were able to access an unresolved nuclear region that became obscured a fter 2015. We also mapped continuum and emission lines beyond the nucleus and found no significant variation within this time frame. These maps also indicate that emission lines are distributed along two main directions\, representing the disc and the radio jet. Furthermore\, the ionization of t he emission lines is compatible with photoionization by an AGN in our whol e 8x8 arcsec² field of view. Lastly\, we detected a strong decrease in du st reddening along the radio jet\, suggesting that the AGN is destroying d ust grains in this region.\n\nhttps://indico.unina.it/event/61/contributio ns/893/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/893/ END:VEVENT BEGIN:VEVENT SUMMARY:Still alive and kicking: a significant outburst in changing-look A GN Mrk 1018 DTSTART;VALUE=DATE-TIME:20230629T143000Z DTEND;VALUE=DATE-TIME:20230629T144500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-943@cern.ch DESCRIPTION:Speakers: Roisin Brogan (Leibniz Institute for Astrophysics Po tsdam)\nMrk 1018 is an extremely unique changing-look AGN\, which has alre ady changed type twice. Almost a decade ago\, it returned from a Seyfert t ype 1 to its original classification of a Seyfert type 1.9. We have been m onitoring Mrk 1018 in the u’-band with STELLA since this last major tran sition. In 2020\, our long-term optical monitoring program detected the mo st significant outburst over the last few years. With a flux increase of a factor ~13\, this outburst alone would have flagged Mrk 1018 as a changin g-look AGN in photometric searches. The outburst is asymmetric in the u’ -band with a rise of ~100 days and a decline of ~200 days. It was confirme d by the ATLAS forced photometry server. Using both STELLA and ATLAS\, we compared the outburst as seen in three optical wavebands. We also followed up with an extensive multi-wavelength dataset in X-ray\, UV\, optical and infrared to compare the AGN components before and after outburst. Optical spectra were taken approximately one year before and after the outburst a nd showed no change. X-ray and UV observations were taken 6 - 7 months bef ore and after. The primary X-ray flux returned to the state before the out burst but the 6.4 keV iron line increased in strength and UV emission was also increased. The IR light curve responded to the optical outburst extre mely quickly. The optical light decay is best described by a linear declin e\, indicating that the increase was not caused by a tidal disruption even t of a star. I will summarise a recently submitted paper on this outburst in 2020\, including speculation as to why why Mrk 1018 changes its energy output repeatedly and in such a drastic manner.\n\nhttps://indico.unina.it /event/61/contributions/943/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/943/ END:VEVENT BEGIN:VEVENT SUMMARY:XMM-Newton Highlights of Black Hole Variability DTSTART;VALUE=DATE-TIME:20230628T090000Z DTEND;VALUE=DATE-TIME:20230628T091500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-871@cern.ch DESCRIPTION:Speakers: Schartel Norbert (ESA)\nWith about 380 refereed pape rs published each year\, XMM-Newton is one of the most\nsuccessful scienti fic missions of ESA ever. Observation of AGNs and their variability is one of the main research fields covered by the observing program of the missi on. The talk highlights XMM-Newton contributions to our current view of Bl ack Holes variability. XMM-Newton observations provide a unique opportunit y to study the vicinity of Supermassive Black Holes (SNBH) and constrain the understanding of the underlying accretion physics. The main focus of t he talk will be the discussion of recent scientific highlight results base d on XMM-Newton observations of SMBHs.\n\nhttps://indico.unina.it/event/61 /contributions/871/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/871/ END:VEVENT BEGIN:VEVENT SUMMARY:AGN in the La Silla QUEST Variability Survey DTSTART;VALUE=DATE-TIME:20230628T094500Z DTEND;VALUE=DATE-TIME:20230628T100000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-812@cern.ch DESCRIPTION:Speakers: Paolo Coppi (Yale University)\nThe La Silla QUEST (L SQ) supernova survey ran for 6 years on the ESO 1m Schmidt telescope at La Silla Chile\, using a large CCD array to replace the photographic plate o f the Schmidt. The survey imaged ~1000 degrees twice per night using a sin gle broad V band filter\, covering a total area of ~25\,000 square degrees from declination ~ -80 to +25 degrees. The survey magnitude limit is V~21 in a single 60 second exposure\, with an average of ~200 visits for any g iven patch of sky and over one thousand square degrees of sky covered by m ore than 1000 visits. Systematic photometric errors from the current diffe rential photometry pipeline are at the 5-10 mmag level for bright point so urces on a good night\, with further improvements expected. The QUEST V fi lter can be absolutely calibrated against SDSS and PanSTARRS g+r data at t he percent level\, enabling LSQ\, for example\, to extend in time the SDSS Stripe 82 variability survey. Although principally designed to find super novae\, the strict survey cadence provides good logarithmic time coverage on timescales from ~30 minutes to ~years\, ideal for probing AGN variabili ty and constraining\, for example\, the parameters of a Damped Random Walk model. We present some highlights of LSQ AGN science. The LSQ dataset sho uld prove useful as a training set to prepare for LSST. Over 1 million LSQ -selected AGN candidates will also be followed up by the upcoming ESO 4MOS T survey.\n\nhttps://indico.unina.it/event/61/contributions/812/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/812/ END:VEVENT BEGIN:VEVENT SUMMARY:What can we learn from correlated radio and X-ray variability? DTSTART;VALUE=DATE-TIME:20230626T133000Z DTEND;VALUE=DATE-TIME:20230626T134500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-863@cern.ch DESCRIPTION:Speakers: Ari Laor (Technion)\nHigh frequency radio emission m ay originate from scales as small as the\ninnermost accretion disk\, and c an thus probe directly the relativistic electrons\nand the magnetic fields in the coronal gas of radio quiet AGN.\n\nI will present simulations of t he time evolution of the distribution functions of\nrelativistic electrons following their injection due to a coronal reconnection event.\nThe elect rons cool through Compton scattering\, producing a pulse of X-ray\nemissio n\, and through synchrotron emission\, producing a pulse of high frequency \nradio emission. Future simultaneous monitoring of X-ray and mm emission may allow \nto probe directly the coronal heating and cooling mechanisms. \n\nI wil also briefly point out the false detections of correlated variab ility when two\nred light curves are correlated\, as we found in a recent study of simultaneous radio\nand X-ray observation of three AGN. I will al so describe how these biases can be \nminimised in future studies.\n\nhtt ps://indico.unina.it/event/61/contributions/863/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/863/ END:VEVENT BEGIN:VEVENT SUMMARY:Simultaneous observations of radio and X-ray variability in radio- quiet Seyfert galaxies DTSTART;VALUE=DATE-TIME:20230627T103000Z DTEND;VALUE=DATE-TIME:20230627T104500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-879@cern.ch DESCRIPTION:Speakers: Sina Chen (Technion)\nRadio variability in some radi o-quiet (RQ) active galactic nuclei suggests emission from regions close t o the central engine\, possibly the outer accretion disc corona. If the or igins of the radio and the X-ray emission are physically related\, their e mission may be temporarily correlated\, possibly with some time delays. We present the results of quasi-simultaneous radio and X-ray monitoring of t hree RQ Seyfert galaxies\, Mrk 110\, Mrk 766\, and NGC 4593\, carried out with the Very Large Array at 8.5 GHz over a period of about 300 days\, and with the Rossi X-ray Timing Explorer at 2-10 keV over a period of about 2 000 days. The radio core variability is likely detected in the highest res olution (A configuration) observations of Mrk 110 and NGC 4593\, with a fr actional variability amplitude of 6.3% and 9.5%\, respectively. A cross-co rrelation analysis suggests an apparently strong (Pearson $r = -0.89$) and highly significant correlation ($p = 1 \\times 10^{-6}$) in Mrk 110\, wit h the radio lagging the X-ray by 56 days. However\, a further analysis of the $r$ values distribution for physically unrelated long time delays\, re veals that this correlation is not significant. This occurs since the Pear son correlation assumes white noise\, while both the X-ray and the radio l ight curves follow red noise\, which dramatically increases the chance\, b y a factor of $\\sim 10^3$\, to get extremely high $r$ values in uncorrela ted data sets. A significantly longer radio monitoring with a higher sampl ing rate\, preferably with a high-resolution fixed radio array\, is requir ed in order to reliably detect a delay.\n\nhttps://indico.unina.it/event/6 1/contributions/879/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/879/ END:VEVENT BEGIN:VEVENT SUMMARY:On the coronal temperature and its variability DTSTART;VALUE=DATE-TIME:20230626T143000Z DTEND;VALUE=DATE-TIME:20230626T144500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-895@cern.ch DESCRIPTION:Speakers: Jia-Lai Kang (University of Science and Technology o f China)\nThe hard X-ray emission universally found in AGN is believed to be produced in the so-called corona\, of which the physical nature remains unclear. A fundamental parameter is the coronal temperature ($T_{\\rm c}$ )\, which could be measured by fitting the high-energy cutoff ($E_{\\rm cu t}$) in the hard X-ray spectra. With multiple NuSTAR observations\, we sea rch for the variation of $T_{\\rm c}$/$E_{\\rm cut}$ in individual sources . We get a small sample of several sources\, which demonstrate an interest ing non-monotonic variation pattern\, with a break point of the photon ind ex $\\Gamma$ detected. Sources are found to be “hotter-softer-when-brigh ter” at $\\Gamma < 2.05$\, but turn into “cooler-softer-when-brighter ” at $\\Gamma > 2.05$. Such a behavior indicates that multiple mechanism s\, for instance\, changes of the coronal geometry and the cooling efficie ncy\, are contributing to the X-ray variability in AGN. Meanwhile\, we are also interested in how $T_{\\rm c}$/$E_{\\rm cut}$ differs from one sourc e to another. We measure the $T_{\\rm c}$/$E_{\\rm cut}$ in a large sample and investigate the correlations between $T_{\\rm c}$ and other parameter s (photon index $\\Gamma$ and Eddington ratio). A strong positive correlat ion between $T_{\\rm c}$ and Γ is detected\, while none between $T_{\\rm c}$ and Eddington ratio. In other words\, counter-intuitively\, hotter cor onae tend to produce softer spectra\, while the accretion rate is not a pr imary determinant of the coronal temperature.\n\nhttps://indico.unina.it/e vent/61/contributions/895/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/895/ END:VEVENT BEGIN:VEVENT SUMMARY:Review: The Physics of Accretion and Outflow in Tidal Disruption E vents DTSTART;VALUE=DATE-TIME:20230629T100000Z DTEND;VALUE=DATE-TIME:20230629T103000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-914@cern.ch DESCRIPTION:Speakers: Jane Dai (The University of Hong Kong)\nTidal disrup tion events of stars provide unique opportunities for probing massive blac k holes in centers of galaxies. Furthermore\, these events are great labor atories for studying black hole accretion and outflow physics. In this tal k\, I will first give a theoretical overview of the accretion\, wind and j et physics tidal disruption events. Then I will discuss our latest discove ries on using general relativistic magnetohydrodynamic and radiative trans fer simulations to understand the accretion disk and outflow in tidal disr uption events and connect theory to the observed signatures.\n\nhttps://in dico.unina.it/event/61/contributions/914/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/914/ END:VEVENT BEGIN:VEVENT SUMMARY:Review: HST view of a multifarious landscape of winds in AGN DTSTART;VALUE=DATE-TIME:20230630T073000Z DTEND;VALUE=DATE-TIME:20230630T080000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-948@cern.ch DESCRIPTION:Speakers: Missagh Mehdipour (Space Telescope Science Institute )\nWinds link the supermassive black holes at the heart of active galactic nuclei (AGN) to their environment. Combined high-resolution UV and X-ray spectroscopy is a crucial tool to advance our understanding of the origin and role of these outflows in AGN. I present results from recent studies i nvestigating the physical connection between different forms of outflows t hat have been found in AGN. I review the UV perspective of warm-absorber o utflows\, transient obscuring winds\, and the ultra-fast outflows (UFOs) u sing spectroscopy with the Hubble Space Telescope (HST). By deciphering th eir variability\, and mapping their ionization and kinematic structure\, n ew insights are gained on the formation and driving of the AGN outflows.\n \nhttps://indico.unina.it/event/61/contributions/948/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/948/ END:VEVENT BEGIN:VEVENT SUMMARY:Review: On the complementarity of time domain techniques for detec ting close binary supermassive black hole candidates: interferometric/(s pectro)astrometric observables and periodicity detection DTSTART;VALUE=DATE-TIME:20230630T130000Z DTEND;VALUE=DATE-TIME:20230630T133000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-913@cern.ch DESCRIPTION:Speakers: Andjelka Kovačević (Department of astronomy\, Facu lty of mathematics\, University of Belgrade)\nThe supermassive black hole (SMBH) binary systems are important for testing the models of SMBH format ion\, comparing the physics of SMBH merging to gravitational wave (GW) det ection\, and determining the stochastic GW background at low frequencies\, just to name a few. \n\nWe present an overview of current efforts on comb ining information from complementary techniques to detect close binary sup ermassive black holes (CB-SMBH\, components bound in a Keplerian pair at m utual distances of less than 0.1 pc). This topic has typically been driven by theoretical work\, but in recent years it has also generated interest in observational astronomy. \n\nA variety of parameters influence CB-SMBH observability\, the bulk of which are dictated by the system's evolutiona ry stage. Throughout electromagnetic domains\, samples of dual SMBH system s separated by kiloparsecs to hundreds of parsecs have been detected. Neve rtheless\, the evidence is not as obvious at subparsec scales due to a lac k of instrumental resolution to separate the binary components features i n highly dimensional observability space.\nMoreover\, a binary SMBH ensemb le should provide a stochastic gravitational wave (GW) background with a d istinct strain form. The Pulsar Timing Array (PTA) might resolve massive o r nearby SMBH binaries from the GW background\, but only during the early inspiral stage of a binary merger\, in addition to supplying GW informatio n for the ensemble of binary systems.\n\nThus\, to expand the explored par ameter space of CB-SMBHs and follow them up with coming nano-Hz GW interfe rometers (or PTA)\, we should employ all available time domain observation s to identify the physical parameters of CB-SMBHs and noteworthy candidate s.\nUsing time domain data sets collected over several techniques\, rather than just one\, should enhance the amount and quality of information on t he observed object. Even if one of the data sets is far more inaccurate th an the other\, this is supposed to be true.\n\nGiven the increasing amount of data from already existing and future large sky surveys\, as well as t he growing population of high resolution imaging tools capable of scanning individual objects with ever-sharper vision\, the combined information fr om these advanced techniques has the potential to uncover a substantial po rtion of CB-SMBH candidates.\n\nhttps://indico.unina.it/event/61/contribut ions/913/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/913/ END:VEVENT BEGIN:VEVENT SUMMARY:Review: Extreme variability around supermassive black holes: Quasi Periodic Eruptions DTSTART;VALUE=DATE-TIME:20230629T131500Z DTEND;VALUE=DATE-TIME:20230629T134500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-904@cern.ch DESCRIPTION:Speakers: Margherita Giustini (Centro de Astrobiología (CAB)\ , CSIC-INTA\, Spain)\nSerendipitously discovered at the end of 2018 in the nucleus of the galaxy GSN 069\, X-ray quasi-periodic eruptions (QPEs) are a new extreme-variability phenomenon associated with supermassive black h oles. QPEs typically appear as sharp and intense burst of X-ray emission\, with a thermal-like spectrum with a temperature $kT \\sim 150$ eV over a much more stable and cooler quiescent level\; they last about one hour and repeat quasi-periodically every few hours\, carrying a few $10^{42-43}$ e rg s$^{-1}$ at each burst. X-ray QPEs have been securely detected in the n uclei of several galaxies since their discovery\, all with low-mass superm assive black holes ($M_{BH} < 10^7 M_{\\odot}$) and different levels of nu clear activity. In this talk I will review the general properties of QPEs and their variegate phenomenology in the QPE-sources (up to 7) detected so far. I will then discuss the physical scenarios invoked to explain this n ew and puzzling extreme-variability X-ray phenomenon\, as well as the more and more evident physical connection of QPEs with tidal disruption events (TDEs) in low-mass galaxies.\n\nhttps://indico.unina.it/event/61/contribu tions/904/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/904/ END:VEVENT BEGIN:VEVENT SUMMARY:Review: Changing-look AGN DTSTART;VALUE=DATE-TIME:20230629T073000Z DTEND;VALUE=DATE-TIME:20230629T080000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-908@cern.ch DESCRIPTION:Speakers: Claudio Ricci (Universidad Diego Portales)\nAGN are known to show flux variability over all observable timescales and across t he entire electromagnetic spectrum. Over the past decade\, a growing numbe r of sources have been observed to show dramatic flux and spectral changes \, both in the X-rays and in the optical/UV. Such events\, commonly descri bed as “changing-look AGN”\, can be divided into two well-defined clas ses. Changing-obscuration objects show strong variability of the line-of-s ight column density\, mostly associated with clouds or outflows eclipsing the central engine of the AGN. Changing-state AGN are instead objects in w hich the optical/UV continuum emission and broad emission lines appear or disappear\, and are typically triggered by strong changes in the accretion rate of the supermassive black hole. In my talk I will review our current understanding of these objects\, and then focus on a few recent X-ray mon itoring campaigns of Changing-state AGN.\n\nhttps://indico.unina.it/event/ 61/contributions/908/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/908/ END:VEVENT BEGIN:VEVENT SUMMARY:Identifying low accretion rate AGN and studying their X-ray variab ility with the EPIC XMM Outburst Detector Ultimate System (EXODUS) DTSTART;VALUE=DATE-TIME:20230626T160000Z DTEND;VALUE=DATE-TIME:20230626T161500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-924@cern.ch DESCRIPTION:Speakers: Maitrayee Gupta (Institute for Research in Astrophys ics and Planetology (IRAP)\, CNRS\, Toulouse\, France)\nTemporal variabili ty of flux across the electromagnetic spectrum is a commonly observed phen omenon in Active Galactic Nuclei (AGN)\, however the phenomenon is not wel l studied in low accretion rate AGN\, primarily due to difficulties identi fying them in X-ray catalogues due to their lower luminosity.\nIn this wor k\, we use our algorithm EXODUS\, which searches for variability in the wh ole of *XMM-Newton*'s EPIC field of view and is agnostic of source detecti on and the number of counts. It accomplishes this by binning the observati ons into short time windows and comparing the pixel counts per window to t he median pixel counts to detect variable sources within the observation\, making EXODUS ideal for studying faint rapid X-ray transients. We apply E XODUS to all of the observations that comprise the 4XMM-DR11 catalogue to create a reliable subset of low Eddington ratio AGN. Understanding these A GN helps us to develop a more complete framework constraining the presence /absence of the corona from the hardness/softness of spectra during the lo w accretion phase. Additionally\, we measure black hole masses\, variabili ty timescales\, and the prominence of their coronal/disc emission by study ing the effect of the different modes of AGN accretion on line-emitting ga s. We compare the results of this study with those of our previous X-ray s tudies on moderate accretion rate AGN selected from the BAT AGN Spectrosco pic Survey sample.\n\nhttps://indico.unina.it/event/61/contributions/924/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/924/ END:VEVENT BEGIN:VEVENT SUMMARY:Review: Continuum reverberation variability of AGN DTSTART;VALUE=DATE-TIME:20230626T074500Z DTEND;VALUE=DATE-TIME:20230626T081500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-907@cern.ch DESCRIPTION:Speakers: Ian McHardy (University of Southampton)\nDetermining the inner geometry of AGN - i.e. the size and location of the central X- ray emitting corona relative to the accretion disc\, the shape\, size and structure of the disc\, the location of the broad line region and its poss ible connection with disc winds\, the location and structure of obscuring material - remains one of the main challenges of astrophysical research. A part from M87 and SgrA*\, whose very inner regions have been imaged by mil limetre global VLBI\, these inner structures are far too small for direct X-ray or optical imaging. We therefore use the technique of 'reverberation mapping'. Here the time lag between direct X-ray emission and lower energ y (UV/optical) emission\, produced by reprocessing of X-rays by the surrou nding material\, gives us the distance from the central X-ray source to th e surrounding material. By measuring that lag in multiple wavebands\, corr esponding to material at a range of temperatures\, we are able to map out at least the temperature structure of the surround material. We can then c ompare our observed structure with the structure that we expect based on t heoretical models of these structures and hence determine whether the mode ls are correct. I will review the observations that have been carried out and their implications for our understanding of the inner geometries of AG N.\n\nhttps://indico.unina.it/event/61/contributions/907/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/907/ END:VEVENT BEGIN:VEVENT SUMMARY:The multifaceted variability of the Seyfert AGN MCG+08-11-11 DTSTART;VALUE=DATE-TIME:20230626T083000Z DTEND;VALUE=DATE-TIME:20230626T084500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-881@cern.ch DESCRIPTION:Speakers: Daniel Kynoch (University of Southampton)\nOver the last decade reverberation mapping (RM) campaigns of active galactic nuclei (AGN) have enabled us to probe their inner regions in unprecedented detai l. Whilst observations have broadly confirmed that the short-term variabil ity of the accretion disc is driven by variations in the X-ray corona a nu mber of puzzles have also emerged\, including: the contribution of the bro ad line region (BLR) to measured lags\; the implied large disc sizes\; the role of disc winds as obscurers or additional reprocessors\; and unexpect edly long X-ray to UV lags.\n \nTo address these issues I present resul ts from a superb new multi-wavelength data set on the bright Seyfert galax y MCG$+$08$-$11$-$11. This major\, high-cadence monitoring campaign\, cond ucted with *Swift* and ground-based observatories\, captured the source in an unusually highly-variable phase compared with previous observations: r apid\, large-amplitude flux changes are observed at all wavelengths. We fi nd that the X-ray and UV-optical lightcurves are much more highly-correlat ed than typically found in similar RM studies. The wavelength-dependent la gs form a spectrum that approximates disc reprocessing predictions. The be haviour of the source was markedly different during an optical RM campaign conducted just a year prior in which only slow and moderate flux changes were seen\; the resultant lag spectrum was very much steeper during this p eriod\, likely because of a stronger contribution from the BLR. Our new r esults further emphasise that a simple\, static reprocessing geometry cann ot explain the observed variability: even in the same source\, different r everberating components (or processes) dominate at different times. This r ich data set provides a golden opportunity to grapple with the dynamic and complex nature of AGN variability\, and I discuss the broader implication s.\n\nhttps://indico.unina.it/event/61/contributions/881/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/881/ END:VEVENT BEGIN:VEVENT SUMMARY:The Ultraviolet/optical Variability and Its Implication for the Ph ysical Processes in Quasars DTSTART;VALUE=DATE-TIME:20230626T084500Z DTEND;VALUE=DATE-TIME:20230626T090000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-877@cern.ch DESCRIPTION:Speakers: Wenyong Kang (University of Science and Technology o f China)\nQuasars are a class of objects in the Universe with very apparen t flux variation. UV/optical variability of such sources has attracted par ticular attention. The radiation in this band is thought to come from the accretion disk. As the central dynamical region of a quasar\, the accretio n disk is theoretically believed to be related to structures such as the c orona and emission line region. Studying the correlations between UV/optic al variability and physical processes occurring in these structures can he lp to constrain and improve the relevant physical models. \n\nWe make a on e-parameter characterization of UV/optical variability amplitude of quasar s using the famous Sloan Digital Sky Survey 10-year light curves in the St ripe 82 region\, and explores the statistical correlations between AGN UV/ optical variability (from the accretion disk) and X-ray emission (from cor ona)\, and between the variability and UV/optical line emission (from line emitting regions). We find that there is an intrinsic positive correlatio n between UV/optical variability and X-ray loudness\, and this correlation occurs mainly at long timescales. This result prefers the physical pictur e depicted by the thermal fluctuation model of accretion disk\, i.e.\, bot h the corona heating and UV/optical variability are related to magnetic tu rbulence in the accretion disk. Then we find a positive intrinsic correlat ion between the variability amplitude and the equivalent width for the bro ad Mg II line\, the C IV line and the [O III] 5007 line. We point out that the possible physical reason behind such correlation could be: a more var iable accretion disk will have a harder and bluer spectral energy distribu tion and therefore increases the emission line equivalent width\; on the o ther hand\, a more variable accretion disk may launch more clouds\, thus i ncreasing the covering factor of emission line region. \n\nIn the future\, with the rapid progress of time-domain surveys\, more extensive/systemati cal studies of AGN variability could significantly promote our understandi ng of AGN variability and relevant physical processes.\n\nhttps://indico.u nina.it/event/61/contributions/877/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/877/ END:VEVENT BEGIN:VEVENT SUMMARY:AGN Continuum Reverberation Mapping DTSTART;VALUE=DATE-TIME:20230626T090000Z DTEND;VALUE=DATE-TIME:20230626T091500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-880@cern.ch DESCRIPTION:Speakers: Hengxiao Guo ()\nReverberation mapping (RM) is a pow erful tool to explore the unresolved central region of active galactic nuc leus (AGN)\, e.g.\, accretion disk. Determining the structure of accretion disks in AGN is fundamental to understanding the growth of supermassive b lack holes\, confirming the standard thin disk theory\, and examining the X-ray reprocessing variability model. However\, recent continuum RM sugges ts that the observed accretion disk size is around three times larger than prediction. In this talk\, I will introduce our recent continuum RM resul ts of bright AGNs in ZTF and the well-known dwarf galaxy NGC 4395. We foun d that the continuum lag is dominated by the diffuse continuum emission\, which may account for the disk-size discrepancy. In addition\, we will int roduce a new method to measure the reverberation black hole mass via conti nuum RM.\n\nhttps://indico.unina.it/event/61/contributions/880/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/880/ END:VEVENT BEGIN:VEVENT SUMMARY:The AGN Variability Archive - AVA: A legacy database of intensive broadband reverberation mapping experiments DTSTART;VALUE=DATE-TIME:20230626T081500Z DTEND;VALUE=DATE-TIME:20230626T083000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-875@cern.ch DESCRIPTION:Speakers: Juan Hernandez Santisteban (University of St Andrews )\nAGN variability carries information about the geometry of the accretion flow which is usually unaccessible to direct imaging methods. In particul ar\, the reverberation signals at optical wavelengths of reprocessed high- energy photons provide insight into the size of the disc itself as well as inclination\, mass accretion rate and the temperature profile of the disc itself. Over the last decade\, we have developed the intensive broadband reverberation mapping technique combining the capabilities of Swift and La s Cumbres Observatory (LCO) to perform long-term (multiple years)\, high-c adence (sub-day)\, multi-wavelength (X-rays to NIR) experiments on ~30 loc al AGN. These IBRM experiments have enabled stringent tests on the predict ions of accretion theory and shown disagreements\, catapulting new avenues to understand AGN variability. In this talk\, I will review the main outc omes of the past IBRM campaigns\, with particular focus on a high Eddingto n accretion source PG 1119+120. Our spectral and temporal decomposition al lowed us to retrieve the signal of two components\; a fast signal consiste nt with the X-ray reprocessing scenario\, and a slow signal with a spectra l energy distribution consistent with diffuse continuum emission from the broad-line region. I will also present the launch of our open-source datab ase - AGN Variability Archive (AVA). This legacy database of processed lig ht curves and spectra of ~10 years of observations taken by both Swift and LCO will enable further studies in accretion flows of supermassive black holes.\n\nhttps://indico.unina.it/event/61/contributions/875/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/875/ END:VEVENT BEGIN:VEVENT SUMMARY:Review: Multiwavelength variability of radio-loud AGN/blazars DTSTART;VALUE=DATE-TIME:20230630T093000Z DTEND;VALUE=DATE-TIME:20230630T100000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-911@cern.ch DESCRIPTION:Speakers: Claudia M. Raiteri (INAF-Osservatorio Astrofisico di Torino)\nRadio-loud AGN are characterized by plasma jets that are formida ble particle accelerators. In blazars we observe jets at a small angle wi th respect to the line of sight\, with consequent relativistic Doppler bea ming of the jet radiation. Therefore\, the extremely variable jet emission dominates the spectral energy distribution of blazars from the radio band up to the gamma rays. I will review the main results obtained through the analysis and interpretation of the multiwavelength variability of radio-l oud AGN\, focussing on blazars.\n\nhttps://indico.unina.it/event/61/contri butions/911/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/911/ END:VEVENT BEGIN:VEVENT SUMMARY:Unveiling the periodic variability patterns of the multiwavelength light emission from the blazar PG 1553+113 DTSTART;VALUE=DATE-TIME:20230630T103000Z DTEND;VALUE=DATE-TIME:20230630T104500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-844@cern.ch DESCRIPTION:Speakers: Tommaso Aniello (INAF OAR)\nThe characteristic varia bility of blazars is being since long time explained by relating it to a w ide range of possible physical processes\, occurring in the accretion disk and/or the jet. The various scenarios include emission spots in the accre tion disk revolving around the supermassive black hole\, magnetohydrodynam ic instabilities in the disk or the jet\, shocks traveling along turbulent jets\, and relativistic effects due to the jet orientation. In the X-ray band\, the background emission generated by the accretion disk seems to ou tshine any possible additional source of variability\, such as the periodi city induced by the presence of a binary black hole in the central engine. The purpose of our work is the search of periodicity in the X-ray\, UV an d optical light curves of the blazar PG 1553+113 with Swift-XRT data spann ing ten years from 2012 to 2022. This source is already known to exhibit p eriodic variability in the optical and the gamma-rays with a period of 2.2 yr only\, we have performed a robust statistical analysis of the light cu rve. Our results confirm that the PG 1553+113 X-ray emission displays a pe riodicity shorter by a factor of ~40% than the gamma-ray one. We also inve stigated the cross-correlations between the light curves of this source in several bands\, in search of possible time delays that could help to disc riminate the spatial distribution of the various emitting region.\n\nhttps ://indico.unina.it/event/61/contributions/844/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/844/ END:VEVENT BEGIN:VEVENT SUMMARY:Flat Spectrum Radio Quasars: 10 years of variability in gamma-ray DTSTART;VALUE=DATE-TIME:20230630T101500Z DTEND;VALUE=DATE-TIME:20230630T103000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-843@cern.ch DESCRIPTION:Speakers: Luigi Pacciani (IAPS-INAF)\nI will show the results of the study of variability for a sample of more than 300 FSRQ in gamma-ray\, focusing on waiting time betw een flares (L. Pac ciani\, A&A\, 2022\, 658\, 164)\, and on flares luminosity and duration. \nThe investigation of waiting t imes revealed that gamma-ray activity can be modeled with overlapping bursts of flares\, with flares uni formly distribuited within each b urst\, and bursts uniformly distribuited with a typical rate of 0.6/y. \nMorerover\, a statistically relevant fas t component with timescale of order of days is revealed. \nFrom this result\, con straints on flares emission mechanisms were derived. \nTimescales derived for FSRQ variability is v ery similar to the findings of Ivezic & MacLeod 2013\, and of Burke 2021 for the damping timescale found in optical for SMBH of 10^8-10^9 solar masses. \nMoreover\, Kelly et al. (2009) aobserved that radio-loud qu asars show an excess opti cal variability for timescales below 1 d\, with a white noise PSD.\nThese similarities sugge st a common origin for such a variability.\n\nhttps://indico.unina.it/even t/61/contributions/843/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/843/ END:VEVENT BEGIN:VEVENT SUMMARY:shocks and variabilities in relativistic AGN jet DTSTART;VALUE=DATE-TIME:20230630T100000Z DTEND;VALUE=DATE-TIME:20230630T101500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-842@cern.ch DESCRIPTION:Speakers: zakaria meliani (Observatoire de Paris)\nOne of the main scenarios to account for the multi-wavelength flux variability observ ed in relativistic jets of active galactic nuclei (AGNs) is based on diffu sive shock acceleration of a population of relativistic electrons on inter nal shocks of various origins. To understand the physical processes associ ated with the observed multi-wavelength emission maps and\nlight curves\, we investigate the physics of the shocks in AGN jet. We simulate variable relativistic jets using the resolving the relativistic magneto-hydrodynami c simulation of fluid equation and the distribution of non-thermal electro ns that are injected in shock regions. Synchrotron emission and radiative transfer are calculated in the post-processing for given observation angle s and frequencies. With our scenario\, we were able to explain the appeara nce of trailing components behind the leading injected variability. The la tter destabilizes the jet\, causing the emergence of oscillating standing shocks and relaxation shocks. Emissions from these regions can dominate th e overall flux or lead to “flare echos” in the light curve.\n\nhttps:/ /indico.unina.it/event/61/contributions/842/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/842/ END:VEVENT BEGIN:VEVENT SUMMARY:Review: Spectroscopic surveys for AGN time-domaine science DTSTART;VALUE=DATE-TIME:20230628T080000Z DTEND;VALUE=DATE-TIME:20230628T083000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-926@cern.ch DESCRIPTION:Speakers: Paulina Lira (Universidad de Chile)\nhttps://indico .unina.it/event/61/contributions/926/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/926/ END:VEVENT BEGIN:VEVENT SUMMARY:Detection of Quasi-Periodic Eruptions in Extragalactic X-Ray Sourc es with Machine Learning DTSTART;VALUE=DATE-TIME:20230630T154500Z DTEND;VALUE=DATE-TIME:20230630T160000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-839@cern.ch DESCRIPTION:Speakers: Robbie Webbe (University of Bristol)\nQuasi-periodic eruptions (QPEs) are a novel phenomenon in high-energy astrophysics\, and to date have only been confirmed to be observed in a small number of AGN. Characterised by high amplitude variability over relatively short timesca les\, QPEs have the potential to provide insights into the strong gravity regimes in the innermost regions of the accretion disks around AGN. To pro vide robust predictions of the physical mechanisms involved we need to fin d more QPE sources to broaden the understanding of the parameter space the y inhabit. We use known observations of QPEs and simulated lightcurves to determine whether machine learning approaches can detect QPE sources\, and then apply these trained networks to the latest release of the XMM Serend ipitous Source Catalogue in the hunt for further candidates.\n\nhttps://in dico.unina.it/event/61/contributions/839/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/839/ END:VEVENT BEGIN:VEVENT SUMMARY:Detecting AGN flares using Gaussian Processes DTSTART;VALUE=DATE-TIME:20230630T160000Z DTEND;VALUE=DATE-TIME:20230630T161500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-837@cern.ch DESCRIPTION:Speakers: Summer McLaughlin (University of Sheffield)\nActive galactic nuclei (AGN) exhibit small amplitude\, short timescale variabilit y in their optical luminosities\, of roughly a few tenths of a magnitude o ver periods of hours to years. But extreme variability of AGN - large lumi nosity changes that are a significant departure from the baseline variabil ity - are known as AGN flares. These events are rare and their timescales poorly constrained\, and most of the literature focuses on individual even ts. With surveys such as the Legacy Survey of Space and Time (LSST) promis ing millions of transient detections per night in the coming decade\, ther e is a need for fast and efficient classification of AGN flares. The probl em with the systematic detection of AGN flares is the ability to detect th em against a variable baseline\; the ability to define a signal as a signi ficant departure from the ever-present variability is a statistical challe nge. Recently\, Gaussian Processes (GPs) have revolutionised the analysis of time-series data in many areas of astronomical research. However\, they have seen limited uptake within AGN astronomy. Here we investigate the ef ficacy of Gaussian Processes to detect AGN flares in both simulated and re al optical light curves. We show that a GP can successfully detect AGN fla res with a false-positive rate of less than one per cent\, and we present examples of AGN that show extreme variability.\n\nhttps://indico.unina.it/ event/61/contributions/837/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/837/ END:VEVENT BEGIN:VEVENT SUMMARY:Searching for different AGN populations in massive datasets with M achine Learning DTSTART;VALUE=DATE-TIME:20230630T153000Z DTEND;VALUE=DATE-TIME:20230630T154500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-835@cern.ch DESCRIPTION:Speakers: Paula Sanchez Saez (ESO)\nBrightness variations of a ctive galactic nuclei (AGNs) provide an alternative way to identify AGN c andidates that could be missed by more traditional selection techniques. I n this talk\, I will first present a new variability and color-based class ifier\, designed to identify multiple classes of transients\, persistently variable\, and non-variable sources\, from the Zwicky Transient Facility (ZTF) Data Release 11 (DR11) and ZTF forced aperture photometry light cur ves of extended and point sources. The main motivation of this model is to identify AGN candidates\, but it can be used for more general time-domain astronomy studies. We used a hierarchical local classifier per parent nod e approach\, to classify a total of 17 classes\, including non-variable ob jects\, transients\, and stochastic and periodic variables. With this mode l\, we have been able to identify AGN candidates at different redshifts an d with different ranges of mass and luminosity. Then\, I will present an a nomaly detection (AD) technique designed to identify AGN light curves with anomalous behaviors. The main aim of this work is to identify changing-st ate AGNs (CSAGNs) at different stages of the transition\, but it can also be used for more general purposes. We modeled ZTF DR5 light curves of 230\ ,458 AGNs with a Variational Recurrent Autoencoder (VRAE) architecture\, t hat allowed us to obtain a set of attributes from the VRAE latent space th at describes the general behavior of our sample. These attributes were the n used as features for an Isolation Forest (IF) algorithm. We used the VRA E reconstruction errors and the IF anomaly score to select a sample of 881 0 anomalies. Bogus candidates dominate these anomalies\, but we were able to identify promising AGNs with anomalous variations.\n\nhttps://indico.u nina.it/event/61/contributions/835/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/835/ END:VEVENT BEGIN:VEVENT SUMMARY:Review: AGN Selection and Characterization in Next-Generation Time -domain Surveys DTSTART;VALUE=DATE-TIME:20230630T150000Z DTEND;VALUE=DATE-TIME:20230630T153000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-901@cern.ch DESCRIPTION:Speakers: Weixiang Yu (Drexel University)\nThe emerging all-sk y multi-epoch surveys (e.g.\, ZTF\, Rubin LSST) have started a new era of time-domain astronomy. The variable nature of AGN across all wavelengths p resents us with unique opportunities to probe AGN physics via time-domain analysis. I will start this talk by reviewing the time-domain analysis tec hniques\, traditional and machine-learning based\, currently employed in AGN selection and characterization. Then\, I will present our most recent work on modeling ~30\,000 quasar UV/optical light curves as second-order c ontinuous-time autoregressive moving-average (CARMA) processes and introdu ce the new software package--EzTao--that we developed to conduct the model ing task. Lastly\, I will preview our ongoing work to improve the current CARMA modeling technique and provide an outlook for further developments t hat will maximize the science output of next-generation time-domain survey s like the Rubin LSST.\n\nhttps://indico.unina.it/event/61/contributions/9 01/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/901/ END:VEVENT BEGIN:VEVENT SUMMARY:Latent SDEs for Modelling Quasar Variability and Inferring Black H ole Properties DTSTART;VALUE=DATE-TIME:20230630T140000Z DTEND;VALUE=DATE-TIME:20230630T141500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-841@cern.ch DESCRIPTION:Speakers: Joshua Fagin (CUNY)\nActive galactic nuclei (AGN) ar e thought to be powered by the accretion of matter around supermassive bla ck holes at the centers of galaxies. The time-dependent variability of an AGN's brightness can provide valuable insights into the physical character istics of its underlying black hole. The variability can be well modeled b y a damped random walk process described by a stochastic differential equa tion (SDE). Upcoming wide-field telescopes such as the Rubin Observatory L egacy Survey of Space and Time (LSST) are expected to observe 100 million AGN in multiple bandpass filters\, so new methods need to be developed to analyze the large volume of light curve data. Latent SDEs are variational auto encoders (VAEs) with a neural SDE as the decoder. Latent SDEs are wel l suited for modeling the AGN time series\, as they explicitly model the u nderlying dynamics. We modify latent SDEs to jointly reconstruct the unobs erved portions of multivariate AGN light curves as well as infer their phy sical properties\, such as the black hole mass. We train our model on a re alistic physics-based simulation of ten-year LSST light curves and find ou r method outperforms a multi-output Gaussian process regression in light c urve reconstruction. Our method has the potential to provide a deeper unde rstanding of the physical properties of black holes and AGN variability an d may be applicable to a wide range of other astronomical times series.\n\ nhttps://indico.unina.it/event/61/contributions/841/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/841/ END:VEVENT BEGIN:VEVENT SUMMARY:Fantastic fits of AGN spectra with FANTASY: case-study of SDSS-RM spectra DTSTART;VALUE=DATE-TIME:20230630T141500Z DTEND;VALUE=DATE-TIME:20230630T143000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-836@cern.ch DESCRIPTION:Speakers: Dragana Ilic (University of Belgrade)\nWe present a new tool FANTASY (Fully Automated pythoN Tool for Agn Spectral analYsis) f or multicomponent fitting of active galactic nuclei (AGN) spectra in the o ptical and near infrared wavelength band. Spectra are modeled by simultane ously fitting the underlying broken power-law continuum\, predefined emiss ion line (narrow\, broad\, coronal\, etc.) lists\, and an Fe II model\, wh ich is here extended to cover the wavelength range from 3700 to 11000A. Th e Fe II model\, founded solely on atomic data\, effectively describes the strong emission of the complex iron ion in the vicinity of the H$\\gamma$ and H$\\beta$ lines\, but also near the H$\\alpha$ line. \nHere we present a case study of the application of FANTASY code on SDSS-RM spectra with S /N>20\, with the aim to study the variability properties of Balmer lines\, as well as of Fe II emission. One interesting finding is that when Fe II emission is present near Hbeta\, it is also detected redward from H$\\alph a$\, potentially contaminating the broad H$\\alpha$ line wings. We show th at the FANTASY code is well optimised for bulk fitting of AGN type 1 spect ra from SDSS\, as it is flexible and easy to use\, thus showing great pote ntial for AGN spectral analysis in the coming spectral surveys.\n\nhttps:/ /indico.unina.it/event/61/contributions/836/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/836/ END:VEVENT BEGIN:VEVENT SUMMARY:Modeling the effects of quasar variability source geometry on ligh t curves DTSTART;VALUE=DATE-TIME:20230630T134500Z DTEND;VALUE=DATE-TIME:20230630T140000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-840@cern.ch DESCRIPTION:Speakers: Bridget Ierace (CUNY/AMNH)\nQuasar variability is of ten modeled simplistically as originating from a point-like lamp post geom etry with a damped random walk time dependence. We create more realistic s imulations of variability propagation through quasar structure using a fle xible and physically motivated quasar model that incorporates lensing by t he SMBH\, disk and broad-line reprocessing\, and extended geometry of the variability source. Using this model\, we derive realistic transfer functi ons and simulate LSST-like multi-band light curves for a wide range of qua sar structure parameters and variability source geometries. We use these t o explore the degree to which deviations from the simplistic lamp post mod els can be determined in upcoming time-domain surveys. We also analyze lig ht curves from SDSS and other existing surveys to make preliminary constra ints on the validity of these models.\n\nhttps://indico.unina.it/event/61/ contributions/840/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/840/ END:VEVENT BEGIN:VEVENT SUMMARY:Quasars with Periodic Variability: Capabilities and Limitations of Bayesian Searches for Supermassive Black Hole Binaries in Time-domain Sur veys DTSTART;VALUE=DATE-TIME:20230630T133000Z DTEND;VALUE=DATE-TIME:20230630T134500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-838@cern.ch DESCRIPTION:Speakers: Caitlin Witt (Northwestern University / Adler Planet arium)\nSupermassive black hole binaries lurk\, often unseen\, in the cent ers of post-merger galaxies\, and numerous electromagnetic surveys are see king evidence of these dynamic duos’ effects on their host galaxies. In this talk I’ll discuss our recent paper\, which analyzed the capabilitie s of promising methods to search for electromagnetic signatures of superma ssive black hole binaries in current and future time domain surveys\, incl uding the Catalina Real-Time Transient Survey (CRTS) and the upcoming Lega cy Survey of Space and Time (LSST). In this paper\, we used Bayesian metho ds to disentangle periodic SMBHB signals from intrinsic damped random walk variability in AGN light curves.\nThrough a careful analysis of parameter estimation and Bayesian model selection\, we investigated the range of pa rameter space for which binary systems can be detected\, and determined th at the false-detection rate depends on the quality of the data and is mini mal in LSST. \nI’ll also discuss the promising implications this work ha s on the possibilities for multi-messenger astrophysics through partnershi ps with pulsar timing arrays\, such as the North American Nanohertz Observ atory for Gravitational Waves (NANOGrav)\, which search for gravitational waves from these binaries.\n\nhttps://indico.unina.it/event/61/contributio ns/838/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/838/ END:VEVENT BEGIN:VEVENT SUMMARY:Time Dependent Line Driven Disc Winds - X-ray Irradiation DTSTART;VALUE=DATE-TIME:20230630T084500Z DTEND;VALUE=DATE-TIME:20230630T090000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-855@cern.ch DESCRIPTION:Speakers: Sergei Dyda (University of Virginia)\nLine driving i s a promising explanation for AGN winds as it provides both a launching me chanism and an explanation for the absorption and emission lines in spectr a. As the community moves towards multi-wavelength and multi-epoch observa tions\, our modelling of AGN systems must likewise follow suit to leverage these new capabilities. For line driving to be a viable acceleration mech anism two conditions must exist in the wind 1) The gas must be sufficientl y\, though not overly\, ionized by X-rays\, so that the gas can interact w ith the UV 2) The UV flux incident on the gas must be high enough to tran sfer sufficient momentum to overcome gravity. We present novel simulations of AGN disc winds using time-dependent\, multi-frequency radiation hydrod ynamics focusing on the problem of gas ionization\, where we model both th e X-ray and UV radiation fields. We consider a suit of models for gas/X-ra y interactions and identify the conditions on scattering and absorption op acities where wind self-shielding can operate and allows line driving to l aunch winds.\n\nhttps://indico.unina.it/event/61/contributions/855/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/855/ END:VEVENT BEGIN:VEVENT SUMMARY:Time variability of ultra-fast outflows in BAL quasars using SALT: C IV equivalent width analysis DTSTART;VALUE=DATE-TIME:20230630T083000Z DTEND;VALUE=DATE-TIME:20230630T084500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-854@cern.ch DESCRIPTION:Speakers: Aromal Pathayappura (Inter-University Centre for Ast ronomy and Astrophysics (IUCAA)\, Pune)\nWe present the results of a South African Large Telescope (SALT) spectroscopic monitoring to study the time variability of C IV BALs in a sample of 64 quasars showing ultra-fast out flow (UFO) with v$_{outflow\,max}$ > 15000 kms$^{-1}$ in their spectra. We also created a sample of non-BAL quasars from SDSS DR12 matched in redshi ft and luminosity. Our UFOs show more blueshift of CIV BEL than that of n on-BALs in the control sample. The fraction of “highly variable” BALs (with fractional change in equivalent width\, $\\frac{\\Delta W}{W}$ > 2) in our sample is considerably higher than that reported for the general BA L population. We find that the strength of variability increases with time \, and for each source\, SALT observations enabled us to look at the varia bility at different time scales ( from as short as < 0.5 years to longer t ime scales of > 7.5 years) in detail. We also show that the fraction of hi ghly variable BALs increases with time\, and for these BALs\, the BAL stre ngthening time scale is found to be considerably shorter than the weakenin g time scales. We found no correlation between BAL variability and quasar properties such as black hole mass and Eddington ratio but found a moderat e correlation with bolometric luminosity for time scales < 2 years. Based on the properties of C IV absorption\, we find weak\, high-velocity\, shal low\, and low-width BALs tend to show more variability. We also classified the BALs according to their absorption profile shape and found detached p rofiles at high velocities showing large variations irrespective of the st rength of absorption. We conclude both the low-equivalent width and high-v elocity nature of BALs are equally important for excess BAL variability. I nterestingly our results suggest that the presence of a distinct BAL troug h at lower velocities increases the chances of observing a highly variable UFO BAL if present. Finally\, using photometric light curves\, we show th at the continuum flux variations may be responsible for the observed BAL v ariability in the majority of the sources where the EW of the BAL decrease s as the continuum increases.\n\nhttps://indico.unina.it/event/61/contribu tions/854/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/854/ END:VEVENT BEGIN:VEVENT SUMMARY:Review: AGN outflows in X-ray DTSTART;VALUE=DATE-TIME:20230630T080000Z DTEND;VALUE=DATE-TIME:20230630T083000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-910@cern.ch DESCRIPTION:Speakers: Elisa Costantini (SRON Netherlands Institute for Spa ce Research)\nIt is clear that an important part of the AGN self sustenanc e\, as well as its connection with the surrounding\, is constituted by pow erful outflows\, detected in a large fraction of objects. Winds can be con sidered as the messenger in the communication between the AGN and the gala xy. \nDifferent wind components co-exist in the same source\, often with d rastically different properties in terms of carried mass and energy. \nIn this talk I will review X-ray winds and their variability as a function of the central engine flux. Several methods are in place to extract importa nt information on the physics and geometry of the outflowing gas. This in turn provide important diagnostic on AGN feedback.\n\nhttps://indico.unina .it/event/61/contributions/910/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/910/ END:VEVENT BEGIN:VEVENT SUMMARY:Multi-messenger observations of supermassive black hole binaries DTSTART;VALUE=DATE-TIME:20230629T151500Z DTEND;VALUE=DATE-TIME:20230629T153000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-827@cern.ch DESCRIPTION:Speakers: Maria Charisi (Vanderbilt University)\nSupermassive black hole binaries are a natural end product of galaxy mergers and should be common in galactic nuclei. They produce bright electromagnetic emissio n and can be identified as quasars with periodic variability in time-domai n surveys. They are also promising sources of low-frequency GWs soon to be detected by pulsar timing arrays (PTAs) with PTAs and time-domain surveys probing the same population of binaries. I will discuss the combination o f time-domain observations with PTA data in a multi-messenger stream\, the parameter space of binaries for which this combination is possible and th e advantages of multi-messenger observations (e.g.\, improved parameter es timation).\n\nhttps://indico.unina.it/event/61/contributions/827/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/827/ END:VEVENT BEGIN:VEVENT SUMMARY:Supermassive black hole binaries and quasar broad emission line va riability DTSTART;VALUE=DATE-TIME:20230629T153000Z DTEND;VALUE=DATE-TIME:20230629T154500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-822@cern.ch DESCRIPTION:Speakers: Jessie Runnoe (Vanderbilt University)\nSupermassive black hole binaries are thought to be an inevitable product of the prevail ing galaxy evolution scenarios where most massive galaxies host a central black hole and undergo mergers over cosmic time. The early stages of this process have been observed in the form of interacting galaxy pairs and wi dely separated dual quasars\, but the close\, gravitationally bound binari es that are expected to follow have so far eluded observation. The detect ion of this population is important because at the smallest separations th ey become bright sources of low-frequency gravitational waves and are prim e targets for multi-messenger detections. One approach to search systemati cally for close supermassive black hole binaries among quasars is based on the hypothesis that the secondary black hole in the system is feeding and the resulting emission lines will be doppler shifted due to its orbital m otion. Binary candidates identified via this method are therefore selected from nearby quasars via substantial (>1000 km/s) shifts of the broad H-be ta lines relative to the systemic redshift. One key test of this search is an ongoing spectroscopic monitoring campaign to look for signs of bulk mo tion of the quasar indicative of orbital motion. I will describe the obser vational research program that I have been leading\, including our most co mpelling candidates and efforts to evaluate the credentials of these candi dates in the face of quasar variability.\n\nhttps://indico.unina.it/event/ 61/contributions/822/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/822/ END:VEVENT BEGIN:VEVENT SUMMARY:Candidate sub-kpc dual SMBHs revealed with variability-induced jit ters of quasars DTSTART;VALUE=DATE-TIME:20230629T154500Z DTEND;VALUE=DATE-TIME:20230629T160000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-821@cern.ch DESCRIPTION:Speakers: Haochen Wang (University of Science and Technology o f China)\nDual super massive black holes at sub-kpc to kpc scales are the products of galaxy mergers and the progenitors of eventually coalescing bi nary SMBHs. Dual AGNs or off-nucleus AGNs may be witnessed if both or one of the dual SMBHs are accreting. Despite its rarity\, such systems are ess ential for learning the dynamical evolution of binary SMBHs as well as the process of galaxy merging. Recently a novel and highly efficient astromet ry-based method named varstrometry has been put forward to search for dual SMBHs at high redshift. This method shows that the unsynchronized flux va riability of off-nucleus and dual AGNs will cause astrometric jitter detec table by Gaia without spatially resolving them. Based on varstrometry we s elect a rare sample of 5 high redshift radio quasars with clear Gaia astro metric jitters\, and with e-MERLIN observations a single compact radio sou rce is revealed for each of them. Clear Gaia-radio offsets of $\\sim$ 9 -- 60 mas are deteced in all but one targets. The observed Gaia jitters appe ar consistent with the expected values. These detected Gaia-radio offsets suggest these candidate dual SMBHs may have projected separations as small as $\\sim$ 0.01 - $0.1''$ ($\\sim$ 0.1 kpc\, depending on the optical flu x ratio of two SMBHs).\n\nhttps://indico.unina.it/event/61/contributions/8 21/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/821/ END:VEVENT BEGIN:VEVENT SUMMARY:The Unanticipated Phenomenology of the Blazar PKS 2131-021: A Uni que Supermassive Black Hole Binary Candidate DTSTART;VALUE=DATE-TIME:20230629T160000Z DTEND;VALUE=DATE-TIME:20230629T161500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-820@cern.ch DESCRIPTION:Speakers: Sebastian Kiehlmann (Foundation for Research and Tec hnology Hellas\, Institute of Astrophysics)\nPKS 2131−021 is a blazar th at shows peculiar variability in the radio light curve: within 45 years of recorded data\, two epochs show strong sinusoidal variation with roughly the same period and phase\, straddling a 20 year period when this variatio n was absent. We apply the Lomb-Scargle periodogram\, weighted wavelet Z- transform and least-squares sine-wave analyses and address two pitfalls th at are commonly ignored in periodicity studies of blazars: First\, blazar light curves typically exhibit red noise variability\, which makes it nece ssary to employ a large set of simulated light curves that reflect such a process. Second\, when no a priori knowledge about the signal period exist s\, the look-elsewhere effect needs to be taken into account over the test ed frequency range. Our statistical analyses demonstrate conclusively\, at the 4.6σ significance level\, that the periodicity in this object is not due to random fluctuations in flux density. A simple model can explain th e sinusoidal variability as a result of modulated Doppler boosting due to the orbital motion of a Supermassive Black Hole Binary (SMBHB). The observ ed period of ~2 years in the rest frame of the source suggests an orbital separation of ∼0.001–0.01 pc. If truly a SMBHB and sufficiently massiv e\, the gravitational waves produced by this system may be detectable with future pulsar timing arrays.\n\nhttps://indico.unina.it/event/61/contribu tions/820/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/820/ END:VEVENT BEGIN:VEVENT SUMMARY:Broad spectral line variability of the changing-look AGN NGC 3516: Role of a dusty broad line region DTSTART;VALUE=DATE-TIME:20230629T141500Z DTEND;VALUE=DATE-TIME:20230629T143000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-831@cern.ch DESCRIPTION:Speakers: Luka C. Popovic (Astronomical Observatory\, Belgrade )\nHere we present our study of the variability of the broad Hbeta line pr ofile of the "changing look" active galactic nucleus (CL-AGN) NGC 3516 ove r a long period (from 1996 to 2021).\nWe model the broad line profiles ass uming that there is emission from the accretion disc superposed with emiss ion from a surrounding region that is outside the disc.\nWe find that in t he Type 1 activity phase (i.e.\, when the strong broad emission lines are observed)\, the broad line region (BLR) is very complex. There is a clear disc-like BLR contributing to the broad line wings and an additional inter mediate line region (ILR) contributing to the line core. In the high activ ity phase\, the ILR emission is close to the center of the line (slightly shifted to red in some cases)\, whereas in the low activity phase (i.e.\, Type 2 phase)\, the ILR component is clearly shifted to blue\, indicating outflow.\nAt different activity stages\, the complex BLR structure can be detected\, indicating that the gas motion remains constant but the line em ission becomes weak. This may be caused by dust entering the interior of t he BLR during the low activity stage\, forming a dusty BLR. This leads to a decrease in ionization and recombination rates\, so that the broad lines almost disappear.\n\nhttps://indico.unina.it/event/61/contributions/831/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/831/ END:VEVENT BEGIN:VEVENT SUMMARY:The optically elusive\, changing look active nucleus in NGC4156 DTSTART;VALUE=DATE-TIME:20230629T140000Z DTEND;VALUE=DATE-TIME:20230629T141500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-824@cern.ch DESCRIPTION:Speakers: Giulia Tozzi (Università di Firenze)\nDespite the i ncreasing number of newly discovered changing look active galactic nuclei (AGN)\, larger samples of known objects and multi-epoch observations are n eeded to shed light on this debated physical mechanism. In this talk\, I w ill report on the changing look AGN in the galaxy NGC4156\, as serendipito usly discovered thanks to data acquired in 2019 at the Telescopio Nazional e Galileo (TNG) during a student observing program. Unlike previous optica l spectra showing no signatures of broad-line emission\, our 2019 TNG data unexpectedly revealed the appearance of broad components in both Hα and Hβ profiles\, along with a rising continuum\, overall pointing to a trans ition from a type 2 towards a (nearly) type 1 AGN. The broad-line emission has been then confirmed by our 2022 TNG follow-up observations\, whereas the rising continuum is no longer detected\, which hints at a further evol ution backwards to a (nearly) type 2. I will discuss possible mechanisms a t the origin of the observed optical variability of NGC4156\, and briefly compare it to what observed in its X-ray multi-epoch observations. Approve d optical (Asiago telescope) and X-ray (Swift) monitoring programs will pr ovide us further insights into the variability of this source\, possibly c onstraining the typical timescales of these changing look events.\n\nhttps ://indico.unina.it/event/61/contributions/824/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/824/ END:VEVENT BEGIN:VEVENT SUMMARY:Late-time X-ray Rebrightening vs. Early Double-peaked Balmer Emiss ion: Investigating Disk Formation in Nuclear Transient AT2020nov DTSTART;VALUE=DATE-TIME:20230629T134500Z DTEND;VALUE=DATE-TIME:20230629T140000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-829@cern.ch DESCRIPTION:Speakers: Nicholas Earl (University of Illinois at Urbana-Cham paign)\nWe present the photometric and spectroscopic analysis of a new nuc lear transient AT2020nov\, an event that shows properties consistent with both TDEs and active galactic nuclei (AGN). Observations in the X-ray show late-time flaring\, coincident with a minor re-brightening in the optical /UV. Evolution in the X-ray hardness ratio follows a trend from hard to so ft\, suggesting a change in the accretion behavior with time. Optical spec troscopy taken both before and after the light curve peak show a blue cont inuum\, with resolved double-peaked Balmer emission and possible Bowen Flu orescence features. The discrepancy between the X-ray and UV/optical photo metry indicates that the radiation sources are initially uncorrelated\, wi th emission arising from physically distinct components. This implies a sc enario in which the optical/UV peak is powered by collisions in the debris streams of a circularizing accretion disk\, while the late-time X-ray and optical/UV bump result from the enhanced accretion rate of the circulariz ed disk. However\, modeling of the double-peaked Balmer features in the sp ectra with an elliptical accretion disk indicates that the disk formed ear ly and fast\, inconsistent with circularization occurring at late times. I n this talk\, I'll discuss how this new event fits into the landscape of n uclear transients generally\, and TDEs/AGN specifically.\n\nhttps://indico .unina.it/event/61/contributions/829/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/829/ END:VEVENT BEGIN:VEVENT SUMMARY:Infrared Dust Echoes and Extreme Coronal Lines: SMBH Environments Unveiled by TDEs DTSTART;VALUE=DATE-TIME:20230629T110000Z DTEND;VALUE=DATE-TIME:20230629T111500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-828@cern.ch DESCRIPTION:Speakers: Megan Newsome (UC Santa Barbara\, Las Cumbres Observ atory)\nWhen stars approach the tidal radius of a supermassive black hole (SMBH) and find themselves unraveled\, the resulting debris stream spirals toward the SMBH and creates a flare whose light can outshine the host gal axy. These tidal disruption events (TDEs) can be used for independent meas ures of black hole masses\, and they offer new windows to study accretion onset and flaring mechanisms near SMBHs. Only recently\, though\, have TDE s offered us glimpses into the sub-parsec local environments near SMBHs. A T 2020mot is a typical UV/optical TDE\, but is uniquely bright in the near -infrared and even shows a later enhancement in brightness along the tail of the light curve. This could be the first TDE to show two "dust echoes\, " indicative of concentric rings of thin dust within 0.1 parsecs of a SMBH \, among the smallest scales at which dust has been inferred near SMBHs. S imilarly\, the recent event AT 2022upj is an extreme coronal line emitter (ECLE) that shares emission line diagnostics in common with the small subs et of ECLEs designated as TDEs. This class of events has been interpreted as another form of a "light echo" of TDEs in gas-rich environments. Events like AT 2020mot and AT 2022upj are novel opportunities to peer into the c losest material of otherwise invisible black holes in quiet galaxies. Stud ying these events will explore the fundamental connections between superma ssive black holes\, galaxy evolution\, and accretion mechanics.\n\nhttps:/ /indico.unina.it/event/61/contributions/828/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/828/ END:VEVENT BEGIN:VEVENT SUMMARY:A repeating partial tidal disruption event discovered by eROSITA DTSTART;VALUE=DATE-TIME:20230629T104500Z DTEND;VALUE=DATE-TIME:20230629T110000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-833@cern.ch DESCRIPTION:Speakers: Zhu Liu ()\nDuring its first two years of the All-Sk y Survey\, SRG/eROSITA uncovered a large sample of X-ray transients associ ated with the nuclei of quiescent galaxies. In this talk\, I will highligh t one exceptional repeating nuclear transient eRASSt J045650-203751 discov ered by SRG/eROSITA. Extensive monitoring with XMM-Newton\, Swift\, NICER\ , and ATCA revealed four repeating X-ray flares and repeating transient ra dio emission. This makes J0456-20 one of the most promising repeating part ial Tidal Disruption Event (pTDE) candidates. A detailed analysis of the a vailable data shows that the characteristic X-ray variability for each fla re can be best explained by the accretion state transitioning between the thermal and the steep power-law states\, accompanied by the formation and destruction of the coronae. This indicates that similar accretion processe s are at work across a broad range of BH masses and accretion rates and th at the corona can be formed and destructed within a few weeks to months. I will also present evidence of a potential evolution of the recurrence tim e of the flares\, hinting at a change in the orbital period of the stellar remnant. This highlights the role of repeating pTDEs as effective probes of the stellar dynamics around supermassive BHs beyond our Galaxy.\n\nhttp s://indico.unina.it/event/61/contributions/833/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/833/ END:VEVENT BEGIN:VEVENT SUMMARY:Extracting physical parameters of SMBH accretion by modeling the X _ray spectra of TDE. DTSTART;VALUE=DATE-TIME:20230629T103000Z DTEND;VALUE=DATE-TIME:20230629T104500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-826@cern.ch DESCRIPTION:Speakers: Richard Saxton (Telespazio for ESA\, ESAC\, Madrid\, Spain)\nThe disruption and subsequent accretion of a star by a super-mass ive black hole (SMBH) provides an excellent laboratory to study a broad ra nge of accretion conditions over timescales as short as months or a few ye ars. We show how a physical model of a relativistic thin accretion disc\, applied to the X-ray spectra of a sample of 19 tidal disruption events (TD E) in the high-accretion thermal phase\, can yield the black hole mass and inner radius of the disc. From this study we offer a possible solution fo r the problem of low apparent total mass accretion in TDE systems and perf orm a sanity check on the hypothesis that the peak optical/UV emission in TDEs is due to the reprocessing of X-ray radiation. \n\nWhen the accretion rate in a TDE drops well below the Eddington limit\, the spectrum is comm only observed to develop a hard X-ray tail\, believed to be due to the Com pton up-scattering of disc photons by a warm electron cloud. We show that \nthis component develops very rapidly in at least one source and use this to constrain the mechanism responsible for the creation of the Comptonisa tion zone.\nFinally we present new data on a further interesting extra-gal actic\, hard X-ray transient\, providing strong support that it was also c aused by a TDE.\n\nhttps://indico.unina.it/event/61/contributions/826/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/826/ END:VEVENT BEGIN:VEVENT SUMMARY:Review: Extreme variability of AGNs: Tidal Disruption Events DTSTART;VALUE=DATE-TIME:20230629T093000Z DTEND;VALUE=DATE-TIME:20230629T100000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-915@cern.ch DESCRIPTION:Speakers: Andreja Gomboc (University of Nova Gorica)\nTidal di sruptions of stars by supermassive black holes were proposed in the 1970s as a possible way of fuelling active galactic nuclei. Following further st udies showing that this mechanism can not supply quasar-level fuelling rat es\, it was realized that bright flares produced by disruptions could be u sed as probes for exploring otherwise quiescent galactic centres.\nIn the last decade the study of Tidal Disruptions Events (TDEs) gained momentum f rom advanced numerical simulations on the theoretical side and from detect ions of dozens of TDEs by wide-field sky surveys on the observational sid e.\n\nI will review the theoretical picture of TDEs\, main mechanisms and parameters affecting the outcome of a stellar encounter with a black hole\ , and their observed characteristics. I will address main open questions s temming from simulations and observations\, and the prospects of Rubin Obs ervatory LSST in discovering TDEs\, and significantly enlarging their sam ple.\n\nhttps://indico.unina.it/event/61/contributions/915/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/915/ END:VEVENT BEGIN:VEVENT SUMMARY:Optical/X-ray variations of the changing-look AGN IRAS23226-3843 DTSTART;VALUE=DATE-TIME:20230629T084500Z DTEND;VALUE=DATE-TIME:20230629T090000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-832@cern.ch DESCRIPTION:Speakers: W. Kollatschny ()\nWe present spectroscopic and phot ometric observations of the changing look AGN\nIRAS23226-3843. This object has previously been classified as a\nchanging-look AGN based on observati ons taken in the 1990s in comparison to\nX-ray data (Swift\, XMM-Newton\, and NuSTAR) and optical spectra taken after\na very strong X-ray decline i n 2017. In 2019\, Swift observations revealed\na strong rebrightening in X -ray and UV fluxes. We took follow-up X-ray\nobservations of IRAS23226-384 3 together with optical spectra from 2019 until\n2021. IRAS23226-3843 show ed a strong X-ray and optical outburst in 2019. It\nvaried in the X-ray co ntinuum by a factor of 5 and in the optical continuum by\na factor of 1.6 within two months. The Balmer and FeII emission-line\nintensities showed c omparable variability amplitudes during the outburst in\n2019. The Halpha emission-line profiles of IRAS23226-3843 changed from a\nblue-peaked profi le in the years 1997 and 1999 to a broad double-peaked\nprofile in 2017 an d 2019. However\, there were no major profile variations in\nthe extremely broad double-peaked profiles despite the strong intensity\nvariations in 2019. One year after the outburst\, IRAS23226-3843 changed its\noptical sp ectral type and became a Seyfert type 2 object in 2020.\nA deep broadband XMM/NuSTAR spectrum was taken during IRAS23226-3843 maximum\nstate in 2019 . This spectrum is qualitatively very similar to a spectrum taken\nin 2017 \, but by a factor of 10 higher. The soft X-ray band appears featureless.\ nThe soft excess is well modeled with a Comptonization model.\n\nhttps://i ndico.unina.it/event/61/contributions/832/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/832/ END:VEVENT BEGIN:VEVENT SUMMARY:The First Sample of "Changing Look" AGN in SDSS-V DTSTART;VALUE=DATE-TIME:20230629T083000Z DTEND;VALUE=DATE-TIME:20230629T084500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-834@cern.ch DESCRIPTION:Speakers: Grisha Zeltyn ()\nRecent advances in time-domain sur veys have revealed dramatic changes to SMBH accretion and AGN appearance o n surprisingly short timescales. Among those\, changing-look AGNs (CL-AGNs ) show the (dis)appearance of broad emission lines and/or the quasar-like continuum\, on timescales of years and sometimes even months. These dramat ic changes may be driven by significant changes to the accretion flow and/ or circumnuclear gas\, and can therefore provide key novel insights into t hese physical components. In this talk I will present the largest sample o f (candidate) CL-AGNs to date\, with >100 sources\, obtained from the firs t year of observations by the recently launched SDSS-V project\, and assis ted by follow-up observations with HET\, Palomar\, and LCOGT. Our sample c overs a redshift range of 0.06 < z < 2.5 and rest-frame transition timesca les lasting from 2 months and up to 19 years. Our preliminary analysis sho ws that CL-AGNs occur at systems with relatively low Eddington ratios\, bu t with no preference for certain BH masses or luminosities. I will highlig ht a particularly extreme CL-AGN\, varying on timescales of <2 months\, wh ose optical spectrum and lightcurve are most likely driven by variable obs curation\, on unprecedentedly short timescales. Our large sample will allo w us to gain insights into the physical mechanisms of CL-AGNs\, with poten tial implications for the unified AGN model and thus for AGN demographics. \n\nhttps://indico.unina.it/event/61/contributions/834/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/834/ END:VEVENT BEGIN:VEVENT SUMMARY:Changing-look AGN in the BAT AGN Spectroscopic Survey DTSTART;VALUE=DATE-TIME:20230629T081500Z DTEND;VALUE=DATE-TIME:20230629T083000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-825@cern.ch DESCRIPTION:Speakers: Matthew Temple ()\nChanging-look (CL) AGN are unique probes of accretion onto supermassive black holes (SMBHs)\, especially wh en simultaneous observations in complementary wavebands allow investigatio ns into the properties of their accretion flows. I will present the result s of a search for CL behaviour in 412 Swift-BAT detected AGN with multiple epochs of optical spectroscopy from the BAT AGN Spectroscopic Survey (BAS S). 125 of these AGN also have 14-195 keV ultra-hard X-ray light curves fr om Swift-BAT which are contemporaneous with the epochs of optical spectros copy. We have discovered eight new CL events\, where the appearance or dis appearance of broad Balmer line emission leads to a change in the observed Seyfert type classification. Combined with known events from the literatu re\, 21 AGN from BASS are now known to display CL behaviour. Nine CL event s have 14-195 keV light curve coverage\, and five of these CL events can b e associated with significant changes in their 14-195 keV flux from BAT. T he ultra-hard X-ray flux is less affected by obscuration and so these chan ges in the 14-195 keV band suggest that the majority of our CL events are not due to changes in line-of-sight obscuration\, and instead must be due to changes in the structure of the accretion disk and broad line region. W e derive a CL rate of 0.7-6.2 per cent on 10-25 yr time-scales\, and show that many transitions happen within at most a few years. Our results motiv ate further multiwavelength observations with higher cadence to better und erstand the variability physics of accretion onto SMBHs.\n\nhttps://indico .unina.it/event/61/contributions/825/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/825/ END:VEVENT BEGIN:VEVENT SUMMARY:New Types of Flares from Accreting Supermassive Black Holes DTSTART;VALUE=DATE-TIME:20230629T080000Z DTEND;VALUE=DATE-TIME:20230629T081500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-830@cern.ch DESCRIPTION:Speakers: Benny Trakhtenbrot (Tel Aviv University)\nA growing number of transient phenomena in galaxy nuclei have recently begun to shed new light on SMBH demographics and the physics of gas accretion onto thes e objects\, tracing events where this accretion has drastically intensifie d\, diminished\, and/or otherwise disturbed. I will present recent results regarding some of these new classes of high-variability phenomena\, focus ing on insights gained thanks to responsive\, multi-wavelength follow-up o bservations. These include “changing look” AGN that occur on surprisin gly short timescales (several weeks)\, and for which we have strong eviden ce for the nature of the transition (i.e.\, accretion vs. obscuration)\; a nd other\, yet poorly understood flaring AGN with broad Bowen fluorescence emission features\, driven by extreme UV radiation that appears within w eeks but lasts for well over a year. While these events observationally d iffer from the tidal disruption events known to date\, the physics behind them may be interlinked. Together\, these extreme events can greatly advan ce our understanding of SMBH accretion\, teach us how and why SMBHs turn t heir accretion “on” and “off”\, and reveal super-Eddington accreti on. I will finally mention how new surveys\, such as the SDSS-V\, will dis cover & survey many more SMBH-related transients.\n\nhttps://indico.unina. it/event/61/contributions/830/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/830/ END:VEVENT BEGIN:VEVENT SUMMARY:STAR-X: a next-generation X-ray and UV explorer to study the restl ess nature of AGN DTSTART;VALUE=DATE-TIME:20230628T111500Z DTEND;VALUE=DATE-TIME:20230628T113000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-813@cern.ch DESCRIPTION:Speakers: Roberto Gilli (INAF - OAS Bologna)\nThe Survey and T ime-domain Astrophysical Research eXplorer (STAR-X\;\nhttp://star-x.xrayde ep.org) is a Medium Explorer class mission\nrecently selected for a compet itive NASA Phase A study. It comprises a\nwide-field\, high-throughput\, h igh-angular-resolution X-ray Telescope\n(XRT) and a complementary UV Teles cope (UVT) on an agile spacecraft\nbus. STAR-X will conduct high-cadence\, deep-and-wide surveys\, and\nrespond rapidly to transient events discover ed by other observatories\nsuch as LIGO\, Rubin/LSST\, Roman/WFIRST\, and SKA.\n\nThe science theme for the mission is “to study the fast\, furiou s and\nforming Universe.” In this talk I will first present an overview of\nthe mission concept and observing capabilities\, and then focus on the \nkey "furious" science pillar\, which will explore feeding and growth of\ nmassive black holes through sensitive\, time-domain studies.\n\nSTAR-X wi ll uniquely probe the physics of rapid accretion that allowed\nthe formati on of the first supermassive black holes\, and will catch\ntransient\, ext reme black hole feeding events\, such as Tidal Disruption\nEvents (TDEs). Critically\, STAR-X will discover TDEs in the X-ray\nband\, providing dire ct evidence for newborn accretion disks. Also\, by\nmonitoring their X-ray and associated UV emission\, STAR-X will\nconstrain the timescales of dis k formation and their\nevolution. Finally\, STAR-X will perform detailed r everberation mapping\nof AGN distributed over a broad range of Eddington r atios\, revealing\nhow the accretion flow geometry depends on the accretio n rate.\n\nhttps://indico.unina.it/event/61/contributions/813/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/813/ END:VEVENT BEGIN:VEVENT SUMMARY:Continuous X-ray monitoring of the south ecliptic pole with eROSIT A DTSTART;VALUE=DATE-TIME:20230628T110000Z DTEND;VALUE=DATE-TIME:20230628T111500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-814@cern.ch DESCRIPTION:Speakers: Teng Liu (Max Planck Institute for Extraterrestrial Physics)\nThe eROSITA all-sky surveys (eRASS) continuously scan the sky \n along great circles crossing the ecliptic poles. This scanning strategy \n covers the full sky every six months and visits the ecliptic poles every \ nfour hours\, leading to much longer exposure time and much higher cadence \nat the ecliptic poles than the majority of the sky. Between Dec. 2019 \ nand Feb. 2022\, the eRASS surveys scanned the full sky more than four \nt imes and observed the ecliptic poles more than 4600 times\, with a total \ nexposure of more than 160ks at the ecliptic poles. Because of the long \n exposure near the confusion limit of eROSITA\, we treated the region \nwit hin 3 degrees of the south ecliptic pole (SEP) separately from the \nmain part of the eRASS surveys and detected X-ray sources with a \npipeline fin e-tuned for such crowed fields. We built a catalog with ~15k \nX-ray sourc es within 3 degrees of SEP (~8k within 1 degree) and \nidentified their mu ltiband counterparts from a few catalogs including \nCatWISE\, NSC-DR2\, S -CVZ\, and GAIA-DR3. Based on multiband colors\, we \nselected AGN from th em and used the AAOmega spectrograph onboard the AAT \ntelescope to follow them up. A large number of the X-ray sources exhibit \nsignificant variab ility\, including a few particular targets that are \npossibly tidal disru ption events\, AGN shutting down or ignition events\, \nor quasi-periodic oscillation cases. We study the normalized excess \nvariance and power spe ctral densities of AGN with X-ray light curves\, \nmeasure their optical p roperties\, e.g.\, black hole mass\, using optical \nspectra\, and analyze the correlation between them.\n\nhttps://indico.unina.it/event/61/contrib utions/814/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/814/ END:VEVENT BEGIN:VEVENT SUMMARY:eROSITA Detection of Cloud Occultation Events in Seyfert AGN\, and Contributions for Clumpy-Torus models DTSTART;VALUE=DATE-TIME:20230628T104500Z DTEND;VALUE=DATE-TIME:20230628T110000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-865@cern.ch DESCRIPTION:Speakers: Alex Markowitz (Nicolaus Copernicus Astronomical Cen ter\, Polish Academy of Sciences)\nRecent years have seen broad observatio nal support for the\ncircumnuclear gas around supermassive black holes to contain a clumpy\ncomponent. In the X-ray band\, individual clouds can ma nifest\nthemselves when they transit the line of sight to the X-ray corona \,\ntemporarily obscuring the X-ray continuum\, and indicating the\ncharac teristics and location of these clouds.\n\nThe eROSITA X-ray telescope abo ard Spectrum X/Gamma is performing\nmultiple all-sky X-ray surveys\, inclu ding monitoring a vast sample of\nAGN and galaxies. Such monitoring can a mplify rare cloud occultation\nevents\, allowing us to accumulate observat ional constraints for\nclumpy-torus models\, including cloud distribution and composition\nparameters.\n\nHere\, we discuss the first cloud occultat ion events detected in a\nSeyfert 1 galaxy by eROSITA: in this Seyfert\, t he soft X-ray flux\ndipped abruptly for $\\sim$ 10-18 months during 2020-2 021\, recovered\,\nbut then dropped a second time by Spring 2022. Our two- year\nmulti-wavelength follow-up campaign included X-ray/UV and ground-bas ed\noptical photometric and spectroscopic observations\, and confirmed tha t\nthe soft X-ray flux dips were caused by partial-covering obscuration\nb y two separate\, single compact clouds near the black hole.\nThe two trans iting clouds are consistent with neutral or lowly-ionized\ngas\, residing at radial distances commensurate with the optical Broad\nLine Region and t he inner dusty torus\, respectively.\n\nhttps://indico.unina.it/event/61/c ontributions/865/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/865/ END:VEVENT BEGIN:VEVENT SUMMARY:Review: AGN variability with eROSITA DTSTART;VALUE=DATE-TIME:20230628T100000Z DTEND;VALUE=DATE-TIME:20230628T103000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-912@cern.ch DESCRIPTION:Speakers: Andrea Merloni ()\neROSITA (extended ROentgen Survey with an Imaging Telescope Array)\, the core instrument on the Russian-Ger man Spektrum-Roentgen-Gamma (SRG) mission has completed 4 scans of the ent ire sky with unprecedented sensitivity in the 0.2-8 keV energy range. I wi ll present an overview of the instrument capabilities\, the current status of the mission\, a few selected early science results focusing on the stu dy of the time domain properties of galactic nuclei.\n\nhttps://indico.uni na.it/event/61/contributions/912/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/912/ END:VEVENT BEGIN:VEVENT SUMMARY:Extreme variability in galactic nuclei detected with eROSITA DTSTART;VALUE=DATE-TIME:20230628T103000Z DTEND;VALUE=DATE-TIME:20230628T104500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-869@cern.ch DESCRIPTION:Speakers: David Homan (Leibniz-Institut für Astrophysik Potsd am)\nThe eROSITA all-sky X-ray survey has provided the basis for a large-s cale search for extreme X-ray variability in extragalactic objects associa ted with accretion changes in AGN. We have combined the survey dataset wit h a multi-wavelength follow-up campaign of the most variable objects. The follow-up observations include optical spectroscopy and X-ray and UV obser vations. This presentation will cover the results of our search for extrem ely variable AGN based on at least four epochs of available eROSITA data. Our sample consists of ~2200 vetted extragalactic sources with significant X-ray changes. As part of our follow-up\, we have collected optical spect roscopic follow-up on ~350 objects\, including repeat spectroscopy for 40% of these. I will introduce our sample selection criteria\, statistics on the detected X-ray variability\, and the observed correlation with optical 'changing-look' behaviour. I will also briefly summarise some of the most interesting individual sources. Finally\, I will discuss our results in t he context of the link between extreme X-ray and optical variability and t he time scales involved in large-scale accretion changes around SMBHs.\n\n https://indico.unina.it/event/61/contributions/869/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/869/ END:VEVENT BEGIN:VEVENT SUMMARY:The search for variable AGN with Gaia DTSTART;VALUE=DATE-TIME:20230628T084500Z DTEND;VALUE=DATE-TIME:20230628T090000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-810@cern.ch DESCRIPTION:Speakers: Maria Isabel Carnerero Martin (INAF-Osservatorio Ast rofisico di Torino)\nThe third release of Gaia data\, published on June 13 \, 2022\, includes not only astrometric and astrophysical parameters of di fferent types of sources\, but also several catalogues of variable sources . Among these\, the catalogue of Gaia variable AGN\, which is described by Carnerero et al. (2022). To identify the variable AGN\, we analyzed the l ight curves of more than 80 million sources observed by Gaia\, selecting 8 70 thousands of them compliant with requirements on their variability prop erties (structure function\, Butler and Bloom metrics\, fractional variabi lity)\, color indices\, astrometric parameters and others. The purpose was to create a variable AGN catalogue as pure as possible. More than 21\,000 of these 870 thousand sources are identified as variable AGN for the firs t time. For each source of the catalogue\, the Gaia multi-band light curve s and the values of a number of variability parameters have been included in the database. In view of the next Gaia DR4\, we are now implementing ne w variability parameters that will be published in the Gaia AGN variabilit y table. They will be useful to the community\, both for carrying out stat istical studies and for AGN classification with machine learning.\n\nhttp s://indico.unina.it/event/61/contributions/810/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/810/ END:VEVENT BEGIN:VEVENT SUMMARY:Review: Restless AGNs in the Legacy Survey of Space and Time DTSTART;VALUE=DATE-TIME:20230628T073000Z DTEND;VALUE=DATE-TIME:20230628T080000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-906@cern.ch DESCRIPTION:Speakers: William Brandt (Penn State University)\nThe Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST)\, aiming to begin in early 2025\, will allow studies of the growing supermassive black hole s (SMBHs) in active galactic nuclei (AGNs) on a truly massive scale. After a brief review of the LSST from an AGN perspective\, I will describe the planned selection of tens of millions of AGNs using the LSST plus multiwav elength data\, including with variability techniques. I will then highligh t examples of exciting LSST AGN variability investigations including massi ve general AGN variability studies\, photometric and spectroscopic reverbe ration mapping\, microlensing of small-scale AGN structure\, transient SMB H fueling events\, and candidate binary SMBHs. I will end by briefly descr ibing the LSST AGN Science Collaboration (AGN SC)\, currently composed of about 160 members spanning the globe. The AGN SC aims to lead many of the described investigations and is preparing for science with the petabyte de luge of LSST data.\n\nhttps://indico.unina.it/event/61/contributions/906/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/906/ END:VEVENT BEGIN:VEVENT SUMMARY:AGN Variability: A ZTF perspective DTSTART;VALUE=DATE-TIME:20230628T083000Z DTEND;VALUE=DATE-TIME:20230628T084500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-811@cern.ch DESCRIPTION:Speakers: Matthew Graham (Caltech)\nThe Zwicky Transient Facto ry (ZTF) has been surveying the visible sky above Dec = -30 on a 2-3 night cadence in $g$\, $r$\, and $I$ for the past five years. With a $5 \\sigma $ detection limit of $g = 20.5$\, this provides hundreds of thousands of n ightly real-time public alerts as well as well-sampled light curves for ov er 3 billion sources. This is an unparalleled data set for both anomaly de tection and population studies of many astrophysical classes but it has be en particularly fruitful for supermassive black holes: both the tens of ti dal disruption events found around quiescent systems but also detecting ne w types of phenomena in active systems. In this talk\, I will review what insights ZTF is providing into the AGN Zoo with changing state quasars\, a mbiguous nuclear transients\, and EM counterparts to stellar mass black ho le mergers as well as the more general properties of the AGN population.\n \nhttps://indico.unina.it/event/61/contributions/811/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/811/ END:VEVENT BEGIN:VEVENT SUMMARY:Review: Optical Variability of AGN with SF and PSD DTSTART;VALUE=DATE-TIME:20230627T150000Z DTEND;VALUE=DATE-TIME:20230627T153000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-916@cern.ch DESCRIPTION:Speakers: Szymon Kozlowski (Warsaw University\, Poland)\nI wil l briefly review basic analysis methods used to describe the typical optic al variability of AGN - structure functions and power spectra. I will disc uss the applicability\, usage\, biases\, and limitations of these methods and present some of the results for the OGLE AGN 20-year-long sample.\n\nh ttps://indico.unina.it/event/61/contributions/916/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/916/ END:VEVENT BEGIN:VEVENT SUMMARY:Periodic variability of Stripe 82 quasar light curves DTSTART;VALUE=DATE-TIME:20230627T161500Z DTEND;VALUE=DATE-TIME:20230627T163000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-851@cern.ch DESCRIPTION:Speakers: Lovro Palaversa ()\nI am going to present the result s of the search for small-amplitude (A_g > 0.03 mag)\, long-period (100 < P[days] < 600) variability in the SDSS Stripe 82 region. This search led t o the discovery of five quasars with apparently periodic light curves. In addition\, I will discuss the line profile variability (presumably linked to the change in the phase of the optical light curve) of the MgII emissio n line of our strongest periodically variable candidate quasar (P=278 days )\, obtained over the past year. With the data collected so far we were no t yet able to exclude the possibility of the object being system of superm assive binary black holes.\n\nOur search was made possible by the precisel y calibrated (1%-2%) Stripe 82 photometry in SDSS ugriz bands\, which cove red a period of approximately 6 years and reached down to r~22 mag. By ana lyzing the Lomb-Scargle periodograms\, we identified the most promising ca ndidates for periodically variable sources. We then cross-matched these ca ndidates with other surveys across the electromagnetic spectrum (photometr y and spectroscopy) to confirm their variability and type. Our analysis wa s supported by Pan-STARRS and ZTF time series\, which provided observation al data spanning more than 20 years.\n\nAll of the identified candidates w ere quasars\, and the highest-ranked one was flagged as a variable source in the Chandra X-ray catalog. The observed periodic behavior of quasars co uld be attributed to various factors\, such as radio jet precession\, tilt ed or warped accretion disks\, tidal disruption events\, and other accreti on-related effects.\n\nhttps://indico.unina.it/event/61/contributions/851/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/851/ END:VEVENT BEGIN:VEVENT SUMMARY:Revealing Changing-Look Quasar Candidates in SDSS Stripe 82 with S DSS\, Pan-STARRS1\, and ZTF data. DTSTART;VALUE=DATE-TIME:20230627T154500Z DTEND;VALUE=DATE-TIME:20230627T160000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-849@cern.ch DESCRIPTION:Speakers: Krzysztof Suberlak (University of Washington)\nWe us e data from the Panoramic Survey Telescope and Rapid Response System 1 Sur vey (Pan-STARRS1\, PS1) to extend the Sloan Digital Sky Survey (SDSS) Stri pe 82 quasar light curves. Combining PS1 and SDSS light curves provides a 15 yr baseline for 9248 quasars–five years longer than prior studies tha t used only SDSS. We fit the light curves with the damped random walk (DRW ) model –  a statistical description of their variability. We correlate the resulting DRW model parameters (asymptotic variability amplitude\, an d characteristic timescale)\, with quasar physical properties (black hole mass\, bolometric luminosity\, and redshift). We also make predictions for the fidelity of DRW model parameter retrieval when light curves will be f urther extended with Zwicky Transient Facility (ZTF) and the Rubin Observa tory Legacy Survey of Space and Time (LSST) data. Finally\, we show how up dated DRW parameters offer an independent method of discovering changing-l ook quasar candidates (CLQSOs). The candidates are outliers in terms of di fferences in magnitude\, and scatter between SDSS and PS1 segments. We ide ntify 40 objects (35 newly reported) exhibiting a tenfold increase in vari ability timescale between SDSS and SDSS - PS1 data. An accompanying large (over 0.5 mag) change in brightness is characteristic of CLQSOs. We summ arize the results of a recent program of spectroscopic follow-up of select CLQSO candidates carried out at the Apache Point Observatory.\n\nhttps:// indico.unina.it/event/61/contributions/849/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/849/ END:VEVENT BEGIN:VEVENT SUMMARY:ZTF constraints on variability from intermediate-mass black hole c andidates DTSTART;VALUE=DATE-TIME:20230627T160000Z DTEND;VALUE=DATE-TIME:20230627T161500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-848@cern.ch DESCRIPTION:Speakers: Ernesto Camacho (Instituto de Astrofisica\, Pontific ia Universidad Catolica de Chile. Millennium Institute of Astrophysics MAS \, Nuncio Monsenor Sotero Sanz 100\, Of. 104\, Providencia\, Santiago\, Ch ile)\nIntermediate-mass black holes (IMBHs) are key pieces in the puzzle o f extragalactic and galactic astronomy\, due to their potential to answer questions related the formation and evolution of supermassive black holes and co-evolution with their host galaxies\, among others. Because of the d ifficulties present when detecting and confirming sources as IMBHs\, they have proven to be an elusive population. Accreting BHs are known to show r andom variability in different spectral bands (optical\, UV\, etc.). We ai m to demonstrate the viability of optical variability as a technique to se lect IMBHs candidates and characterize a sample of IMBHs obtained from the literature. Using ZTF forced photometry on the difference image\, and var ious variability features\, we obtain a high-confidence IMBHs candidates s ubgroup. We aim to study the multi-wavelength properties of the selected s ubsample and discuss it's implications in the AGN paradigm.\n\nhttps://ind ico.unina.it/event/61/contributions/848/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/848/ END:VEVENT BEGIN:VEVENT SUMMARY:Ensemble Power Spectral Density of AGN in optical bands DTSTART;VALUE=DATE-TIME:20230627T133000Z DTEND;VALUE=DATE-TIME:20230627T134500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-853@cern.ch DESCRIPTION:Speakers: Vincenzo Petrecca (Università di Napoli Federico II )\nVariability of AGN in all wavelengths has been known for decades\, with timescales ranging from days to years. However\, the physical mechanisms driving such variability are still unclear. X-ray Power Spectral Densities (PSDs) are usually well represented by power laws with slopes α ~ -1 at low frequencies\, and α ~ -2 at high frequencies. Similar power-law trend s have also been observed in UV/optical bands\, but with a much lower brea k frequency. Optical variability is typically studied through Structure Fu nction (SF) and modeled with a Damped Random Walk (DRW)\, implying a PSD w ith slopes at low and high frequencies\, α=0\, α=-2\, respectively. Desp ite the good agreement of the DRW model on timescales from several months to a few years\, many works show significant deviations on both longer and shorter timescales\, along with strong uncertainties in determining the p osition of the break. \n\nI will present a completely model independent st udy of AGN optical variability through ensemble PSD analysis on archival d ata. The wealth of information about bolometric luminosities and black hol e masses enable the study of correlations between the variability amplitud e and the AGN physical properties. PSD also has the advantage that its est imates at different frequencies are uncorrelated and with well known stati stical properties. Moreover\, as X-ray variability is usually studied thro ugh PSDs\, using the same tool for optical bands provides better constrain ts on different variability models. Results from this analysis will be fur ther boosted by the upcoming Legacy Survey of Space and Time (LSST)\, whic h will increase both the size of the sample and the temporal baseline\, co mpared to previous surveys.\n\nhttps://indico.unina.it/event/61/contributi ons/853/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/853/ END:VEVENT BEGIN:VEVENT SUMMARY:Extracting AGN variable component properties with long-term optica l photometry DTSTART;VALUE=DATE-TIME:20230627T140000Z DTEND;VALUE=DATE-TIME:20230627T141500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-852@cern.ch DESCRIPTION:Speakers: Hartmut Winkler (University of Johannesburg)\nI pres ent initial results from long-term (*U*)*BV*(*u'*)*g'r'* photometry with t he Las Cumbres Observatory robotic telescope network of a sample of ~80 AG N with a cadence of typically 1 month. The sample includes multiple repres entatives from the following AGN sub-categories: NLS1 with strong Fe II em ission\; Seyferts with Keplerian rotator broad line profiles\; Seyferts wi th strong broad He II emission\; obscured AGN\; known Changing-look AGN\; blazars. I utilise the flux variation gradient (FVG) method to determine t he colour of an AGN's variable component. In most cases the FVG method als o enables the separation of the variable and non-variable optical flux con tributions and the estimation of the nuclear reddening. Since commencing t his programme three years ago variations have been confirmed in >80% of th e sample\, and nuclear colours with an accuracy of 0.1 mag or better in *B -V* have been determined for half of the observed AGN. From these colours I determine the intrinsic variable component optical flux distributions an d examine if and how these differ between the AGN sub-categories mentioned earlier. I briefly discuss how this constrains physical models of the var iable parts of these AGN. Additional results include the indication that N LS1 with strong Fe II emission display lower optical variability amplitude s and that the reddening law for the dust obscuring some AGN differs to th at applicable to typical interstellar dust.\n\nhttps://indico.unina.it/eve nt/61/contributions/852/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/852/ END:VEVENT BEGIN:VEVENT SUMMARY:Studying Quasar accretion discs with massive optical variability s urveys DTSTART;VALUE=DATE-TIME:20230627T141500Z DTEND;VALUE=DATE-TIME:20230627T143000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-850@cern.ch DESCRIPTION:Speakers: Patricia Arévalo (Instituto de Física y Astronomí a\, Universidad de Valparaíso)\nQuasars optical variability gives us clue s to understand the accretion disc around supermassive black holes. We can expect variability properties to correlate with the main physical propert ies of the accreting black hole\, i.e.\, its mass and accretion rate. It h as been established that the relative amplitude of optical variability ant i-correlates with the accretion rate and luminosity.The dependence of the variance on black hole mass has remained elusive\, and contradicting resul ts\, including positive\, negative\, or no correlation\, have been reporte d. In this work\, we show that the key to these contradictions lies in the timescales of variability studied (e.g.\, the length of the light curves available). By isolating the variance on different timescales as well as m ass and accretion rate bins we show that there is indeed a negative correl ation between black hole mass and variance and that this anti-correlation is stronger for shorter timescale fluctuations. The behavior can be explai ned in terms of a universal variability power spectrum for all quasars\, r esembling a broken power law where the variance is constant at low tempora l frequencies and then drops continuously for frequencies higher than a ch aracteristic frequency f_b\, where f_b correlates with the black hole mass .  Furthermore\, to explain all the variance results presented here\, not only the normalization of this power spectrum must anti-correlate with th e accretion rate\, but also the shape of the power spectra at short timesc ales must depend on this parameter as well. In this talk I will present th e possible interpretations of the dependence of power spectral shape on bo th parameters as well as the data supporting the results.\n\nhttps://indic o.unina.it/event/61/contributions/850/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/850/ END:VEVENT BEGIN:VEVENT SUMMARY:Uncovering Optical Quasar Variability After 20 Years DTSTART;VALUE=DATE-TIME:20230627T134500Z DTEND;VALUE=DATE-TIME:20230627T140000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-846@cern.ch DESCRIPTION:Speakers: Zachary Stone (University of Illinois at Urbana Cham paign)\nAll quasars show a common stochastic variability\, seen across var ious observed wavelengths and timescales. The origin of this variability i s still uncertain\, though variability in the optical is thought to stem f rom processes in the accretion disk around the SMBH. Time-series variabili ty analysis presents a unique way to probe a quasar's geometry and dynamic s in this regime without ultra-fine spatial resolution.\n\nOptical quasar variability has been shown to be well-described by the Damped Random Walk (DRW) model\, which is parameterized by a characteristic timescale $\\tau_ {\\rm DRW}$ and amplitude $\\sigma_{\\rm DRW}$. A set of these parameters for a sample of quasars can be used to describe the variability statistica lly\, which can then be related to physical properties of the accretion di sk and its SMBH. For example\, it has been shown that $\\tau_{\\rm DRW}$ c orrelates with the SMBH mass $M_{BH}$.\n\nTo investigate the validity and bias of the DRW model\, in a recent work\, we perform DRW-fitting analysis on multi-band 20-year-long optical quasar light curves for a sample of ne arly 200 quasars\, the longest baseline so far in DRW analysis.\n\nWe find that many of the timescales are still biased\, though they are becoming l ess biased as baselines increase. We also find\, using more flexible model s\, that the group (i.e.\, ensemble) power spectrum of the sample differs from the theoretical DRW model power spectrum on short timescales ($\n\nht tps://indico.unina.it/event/61/contributions/846/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/846/ END:VEVENT BEGIN:VEVENT SUMMARY:Review: AGN Optical/UV Variability: pleasures and pains DTSTART;VALUE=DATE-TIME:20230627T130000Z DTEND;VALUE=DATE-TIME:20230627T133000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-905@cern.ch DESCRIPTION:Speakers: Demetra De Cicco (Università degli Studi di Napoli "Federico II")\nVariability characterizes AGN at all wavelengths and is ob served both in continuum and line emission. My talk aims at giving an over view of AGN optical/UV variability\, focusing on the main results and chal lenges from the past decades.\n\nhttps://indico.unina.it/event/61/contribu tions/905/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/905/ END:VEVENT BEGIN:VEVENT SUMMARY:Review: AGN accretion disk physics and variability DTSTART;VALUE=DATE-TIME:20230627T094500Z DTEND;VALUE=DATE-TIME:20230627T101500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-902@cern.ch DESCRIPTION:Speakers: Omer Blaes (University of California\, Santa Barbara )\nTraditional accretion disk models have always had problems explaining a variety of observed features of AGN\, particularly the short wavelength S ED in the ultraviolet and beyond\, and the rapid variability. I will revi ew possible resolutions to these problems\, including the effects of outfl ows\, opacity-driven convection in the disk\, and magnetically elevated di sks.\n\nhttps://indico.unina.it/event/61/contributions/902/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/902/ END:VEVENT BEGIN:VEVENT SUMMARY:Modified models of radiation pressure instability as a potential c ause of Changing-Look AGN phenomenon DTSTART;VALUE=DATE-TIME:20230627T110000Z DTEND;VALUE=DATE-TIME:20230627T111500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-858@cern.ch DESCRIPTION:Speakers: Marzena Sniegowska (Tel Aviv University)\nApart from regular\, low-level stochastic variability\, some AGNs occasionally show exceptionally large changes in luminosity\, spectral shape\, and/or X-ray absorption. The most notable are the changes of the spectral type when the source classified as a Seyfert 1 becomes a Seyfert 2 galaxy or vice versa . Thus a name was coined as 'Changing-Look AGN' (CL AGN). The origin of th is phenomenon is still unknown\, but for most of the sources\, there are s trong arguments in favor of intrinsic changes.\n\nUnderstanding the nature of such rapid changes is a challenge to the models of black hole accretio n flows since the timescales of the changes are much shorter than the stan dard disk viscous timescale\, related to changes in angular momentum distr ibution.\nWe aim to model the CL AGN phenomenon using the time-dependent e volution of a black hole accretion disk unstable due to the dominant radia tion pressure. We use a 1-dimensional\, vertically integrated scheme\, and focus on the variability timescales and amplitudes\, which can be regulat ed by the action of large-scale toroidal magnetic fields and the presence of an inner optically thin flow\, like Advection-Dominated Accretion Flow (ADAF). We thus modify the inner boundary condition of the cold disk flow\ , and we mimic the formation of the MRI-inactive zones\, that suppress ins tabilities\, by parameterizing their relative importance according to a lo cal accretion rate. We succeed to model the timescales of tens of years th at correspond to timescales of observed repetitive outbursts in CL AGN\, s uch as NGC 1566 or NGC 4151.\nHowever\, other interpretations of quasar va riability are still open and most probably more than one mechanism is resp onsible for changes observed in CL AGN.\n\nhttps://indico.unina.it/event/6 1/contributions/858/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/858/ END:VEVENT BEGIN:VEVENT SUMMARY:Hydrodynamical simulations of the variable accretion on to our clo sest SMBH DTSTART;VALUE=DATE-TIME:20230627T101500Z DTEND;VALUE=DATE-TIME:20230627T103000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-857@cern.ch DESCRIPTION:Speakers: Jorge Cuadra (Universidad Adolfo Ibáñez)\nSgr A$^* $\, located only 8 kpc away\, allows us to study in detail the accretion p rocess on to a super-massive black hole. Direct observations show that th e black hole luminosity varies on different time-scales\, but remains extr emely dim\, despite the (disputed) presence of a cold gaseous disc. Howev er\, indirect evidence reveals that it was several orders of magnitude bri ghter just a few hundred years ago\, and perhaps an AGN a few million year s in the past. Unlike any other super-massive black hole\, in our Galacti c centre we can directly observe the source of the material feeding the ac cretion\, which in this case corresponds to a few dozen young\, massive st ars\, with powerful stellar winds. After reviewing the observed variabili ty\, I will describe our hydrodynamical models of the gas surrounding Sgr A$^*$\, originating from the observed stars\, with known orbits and stella r wind properties. Our simulations show that these winds can naturally ac count for the formation of both the hot\, inefficient accretion flow and t he cold disc. Moreover\, the stellar orbits\, and the formation of cold c lumps and streams\, make the accretion vary on time-scales of decades to m illennia\, potentially explaining the observed behaviour.\n\nhttps://indic o.unina.it/event/61/contributions/857/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/857/ END:VEVENT BEGIN:VEVENT SUMMARY:Stellar graveyards in AGN disks - prospects for multi-messenger tr ansients DTSTART;VALUE=DATE-TIME:20230627T104500Z DTEND;VALUE=DATE-TIME:20230627T110000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-856@cern.ch DESCRIPTION:Speakers: Imre Bartos ()\nActive Galactic Nuclei (AGNs) can co llect stars and stellar remnants from the vicinity of the galactic center into the inner plane of the AGN disk. The dense population of stellar obje cts give rise to a wealth of interactions from stellar-mass black hole col lisions to the tidal disruption of stars on stellar-mass black holes. Thes e transients are promising multi-messenger sources from gravitational wave s to radiation across the electromagnetic spectrum. I will discuss what we currently know about AGN-assisted mergers and disruptions so far\, and hi ghlight the most promising future observational directions.\n\nhttps://ind ico.unina.it/event/61/contributions/856/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/856/ END:VEVENT BEGIN:VEVENT SUMMARY:Review: Reverberation Mapping of Emission Lines in AGNs: Last Deca de and Future Prospects DTSTART;VALUE=DATE-TIME:20230627T073000Z DTEND;VALUE=DATE-TIME:20230627T080000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-909@cern.ch DESCRIPTION:Speakers: Pu Du (Institute of High Energy Physics\, Chinese Ac ademy of Sciences)\nReverberation Mapping (RM) is a powerful technique for studying the geometry and kinematics of the broad-line regions in AGNs\, as well as measuring the masses of supermassive black holes. This is achie ved by observing the delayed response of broad emission lines with respect to the varying continuum. Significant progress has been made over the pas t decade\, with the accumulation of RM data in different emission lines of various types of AGNs\, as well as the development of more sophisticated analysis methods. In this talk\, I will try to review the past 10 years of RM of emission lines in AGNs and discuss future prospects.\n\nhttps://ind ico.unina.it/event/61/contributions/909/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/909/ END:VEVENT BEGIN:VEVENT SUMMARY:Exploring the jet-BLR connection: flare-induced variability in the optical emission lines DTSTART;VALUE=DATE-TIME:20230627T090000Z DTEND;VALUE=DATE-TIME:20230627T091500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-845@cern.ch DESCRIPTION:Speakers: Marco Berton (European Southern Observatory (ESO))\n PKS 2004-447 is a narrow-line Seyfert 1 (NLS1) galaxy harboring relativist ic jets capable of producing gamma-ray emission. On 2019-10-25\, the Fermi Satellite detected a gamma-ray flare from this source for the first time. Thanks to coordinated spectral observations\, we had a unique opportunity to study the behavior of the broad-line region (BLR) during a jet flare a nd searching for optical variability. Despite the obvious importance of un derstanding whether the jet can interact with the BLR\, this aspect has no t been thoroughly investigated. In my talk\, I will introduce the peculiar nature of PKS 2004-447\, which has remained poorly understood since its i dentification more than twenty years ago. I will also report on the result s of our FORS2 and X-Shooter observations carried out before\, during\, an d after the flare. During the high-energy event\, a flux excess redshifted by 250 km/s is clearly seen in the Balmer\, Paschen\, and He I permitted lines. Such behavior has never been observed before\, and interestingly th is new emission feature is no longer visible 1.5 years after the flare\, i ndicating a possible causal connection with the gamma-ray flare. The emiss ion lines coming from the same atomic transition series show a similar vel ocity offset for this "red excess"\, but the offset changes for different line series. This discovery suggests that the relativistic jet can affect the physics of the BLR in this peculiar AGN\, and that flaring activity ca n lead to the formation of additional and localized broad emission compone nts. Our results highlight the importance of optical spectroscopy for flar ing jetted AGN\, and that our understanding of the jet-BLR connection is s till very limited. These results will be used as a starting point for futu re dedicated studies of this kind.\n\nhttps://indico.unina.it/event/61/con tributions/845/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/845/ END:VEVENT BEGIN:VEVENT SUMMARY:Investigating the high-luminosity end of the H beta size-luminosit y relation based on the 6-year Seoul National University Monitoring Projec t (SAMP) DTSTART;VALUE=DATE-TIME:20230627T081500Z DTEND;VALUE=DATE-TIME:20230627T083000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-818@cern.ch DESCRIPTION:Speakers: Shu Wang (Seoul National University)\nReverberation mapping (RM) of Active Galactic Nuclei (AGNs) is the primary method to mea sure AGN broad line region (BLR) sizes and black hole (BH) masses. Most ob jects in the current H$\\beta$ RM sample are low-to-intermediate luminosit y AGNs with only a few objects having $L_{5100}\\geq10^{44.5}$ erg/s. Here we present the latest results from our 6-year Seoul National University A GN Monitoring Project (SAMP). With hundreds of nights of regularly sampled spectroscopic/photometric observations\, we successfully obtain reliable H$\\beta$ lags and BH masses for 24 objects in the luminosity range of $L_ {5100} = 10^{44.1\\sim45.6}$ erg/s. The BLR sizes of these objects are gen erally smaller than the expectation from Bentz et al. relation. By applyin g an uniform lag analysis to literature H$\\beta$ RM light curves and sele cting reliable lag measurements to combine with SAMP measurements\, we fin d the current H$\\beta$ size-luminosity relation has a slope of $0.41\\pm0 .02$ with an intrinsic scatter of 0.19 dex. We confirm that the accretion rate / UV-optical spectral energy distribution is related to this shallowe r slope. In addition\, we will present the H$\\beta$ velocity resolved lag measurements for $\\sim20$ AGNs and discuss the implication of these resu lts on the BLR properties.\n\nhttps://indico.unina.it/event/61/contributio ns/818/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/818/ END:VEVENT BEGIN:VEVENT SUMMARY:Resolving the BLR with VLTI/GRAVITY DTSTART;VALUE=DATE-TIME:20230627T080000Z DTEND;VALUE=DATE-TIME:20230627T081500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-817@cern.ch DESCRIPTION:Speakers: Daryl Joe Santos (MPE)\nWith VLTI/GRAVITY and near-i nfrared (NIR) interferometry\, we can directly spatially resolve the broad -line region (BLR) to probe its physics and derive supermassive black hole (SMBH) masses via dynamical modelling. This method provides an independen t test of the assumptions of reverberation mapping (RM)\, which has been t he main method used so far to study the small scales associated with the B LR. In this talk\, I will present our study of 7 type 1 AGNs observed with VLTI/GRAVITY. All of our studied BLRs can be well described by a thick\, rotating disk of clouds. For each individual AGN\, though\, we can trace s ubstructure and non-circular motions. For Mrk 509 and PDS 456 in particula r\, we find evidence for significant outflows. Interestingly\, we find sig nificant spatial offsets between average photocenters of the hot dust cont inuum and the BLR (ranging from $\\sim$17$\\mu$as to 140$\\mu$as)\, which seem to follow a tight relationship with the AGN luminosity. I will discus s our interpretation of this relation\, together with the implications of our results with RM\, the physics of the BLR\, and scaling relations such as the radius-luminosity (R-L) and black hole mass – stellar velocity di spersion ($M_{\\rm BH}$ - $\\sigma_*$) relations.\n\nhttps://indico.unina. it/event/61/contributions/817/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/817/ END:VEVENT BEGIN:VEVENT SUMMARY:Inferring long-term variability on scales of 10^4-5 yrs using exte nded emission line regions DTSTART;VALUE=DATE-TIME:20230627T084500Z DTEND;VALUE=DATE-TIME:20230627T090000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-816@cern.ch DESCRIPTION:Speakers: Carolina Finlez ()\nWe present the analysis of a fiv e nearby AGN that present extended emission line regions (EELRs) observed with the VLT/MUSE spectrograph. Spatially resolved emission line diagnosti cs indicate that the EELRs have been primarily photo-ionized by their AGN. The stellar and gas component kinematics indicate past merger or galaxy i nteractions that have perturbed all of these sources.\nWe generate sets of photo-ionization models and fit these to different regions along the diff erent EELRs\, covering distances of tens of kpc from the centre. These mod els allow us to estimate the bolometric luminosity required at different r adii to excite the gas at the observed state. Our results suggests a syste matic gradual decrease in AGN luminosity\, and hence the accretion rate on to the SMBH\, by a factor ∼ 100 over the past ~ 10^4 yr for every galaxy in the sample. This allow us to probe AGN variability on scales larger th an possible for human timescales.\n\nhttps://indico.unina.it/event/61/cont ributions/816/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/816/ END:VEVENT BEGIN:VEVENT SUMMARY:MgII radius-luminosity relation: applications to the BLR structure and cosmology DTSTART;VALUE=DATE-TIME:20230627T083000Z DTEND;VALUE=DATE-TIME:20230627T084500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-815@cern.ch DESCRIPTION:Speakers: Michal Zajaček (Masaryk University)\nBy long-term s pectroscopic and photometric monitoring of three luminous intermediate-red shift quasars (CTS C30.10\, HE 0413-4031\, HE0435-4312) by the SALT telesc ope\, we have been able to progressively constrain the parameters of the M gII radius-luminosity (R-L) relation (Czerny+2019\, Zajacek+2020\, Zajacek +2021). The MgII line variability is comparable to the continuum variabil ity and the MgII light curve is significantly correlated with respect to c ontinuum light curve. Thanks to that\, we were able to infer the rest-fram e time delays of the MgII emission\, which are 276\, 303\, and 296 days fo r CTS C30.10\, HE 0413\, and HE0435\, respectively. In combination with SD SS and OzDES reverberation mapping programs\, which monitored lower-lumino sity sources\, the MgII R-L relation is constrained well using 94 sources up to now. The luminous quasars are crucial for enhancing the R-L correla tion. The MgII R-L relation has a large vertical scatter of ~0.39 dex and a slope of ~0.3\, which is in tension with the simple photoionization theo ry. We compare the MgII R-L relation with optical Hbeta\, optical and UV FeII relations. The flatter slope of MgII R-L relation with respect to oth er R-L relations could be caused by the bias towards higher-Eddington\, in termediate-redshift sources whose time delays are shortened for a given lu minosity. In addition\, we show that MgII R-L relation parameters are inde pendent of the adopted cosmological model\, and thus the monitored quasars can be standardized and applied for constraining cosmological parameters of different models (flat and non-flat cosmological models with general dy namical dark energy). Inferred cosmological constraints are weak but consi stent with better established cosmological probes.\n\nhttps://indico.unina .it/event/61/contributions/815/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/815/ END:VEVENT BEGIN:VEVENT SUMMARY:X-ray polarimetry of Seyferts and the nature of the hot corona DTSTART;VALUE=DATE-TIME:20230626T163000Z DTEND;VALUE=DATE-TIME:20230626T164500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-868@cern.ch DESCRIPTION:Speakers: Francesco Ursini ()\nWe present the first X-ray pola rimetric measurements of three Seyfert 1 galaxies with IXPE\, the NASA/ASI mission operating as of December 2021. The results allow us to directly c onstrain the geometrical shape of the hot corona for the first time. We di scuss the implications for the physical interpretation of X-ray variabilit y in these sources.\n\nhttps://indico.unina.it/event/61/contributions/868/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/868/ END:VEVENT BEGIN:VEVENT SUMMARY:X-ray variability of SDSS quasars DTSTART;VALUE=DATE-TIME:20230626T161500Z DTEND;VALUE=DATE-TIME:20230626T163000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-870@cern.ch DESCRIPTION:Speakers: Guido Risaliti (Università di Firenze)\nI present t he analysis of a sample of several hundred SDSS quasars with multiple sere ndipitous XMM-Newton observations. The X-ray to UV luminosity relation all ows to predict the average X-ray flux\, and to select only the X-ray obser vations that are deep enough to remove any bias towards higer-than-average flux states. The optical/UV SDSS spectrum allows to investigate the relat ion between X-ray variability and the total luminosity\, the black hole ma ss\, and the Eddington ratio. Considering that the optical/UV and X-ray ob servations are not correlated\, I conclude that most of the "intrinsic" di spersion of the X-ray to UV relation is due to X-ray variability.\n\nhttps ://indico.unina.it/event/61/contributions/870/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/870/ END:VEVENT BEGIN:VEVENT SUMMARY:X-ray variability properties of the BASS unobscured AGN from XMM-N ewton observations. DTSTART;VALUE=DATE-TIME:20230626T154500Z DTEND;VALUE=DATE-TIME:20230626T160000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-866@cern.ch DESCRIPTION:Speakers: Alessia Tortosa (Instituto de Estudios Astrofísicos \, Facultad de Ingeniería y Ciencias\, Universidad Diego Portales)\nI wil l present the analysis of the X-ray variability properties of the Seyfert 1 Galaxies belonging to the BAT AGN Spectroscopic Survey (BASS) using XMM- Newton observations. This sample includes more than 500 observations of 15 1 local AGN (medium redshift z=0.06). The aim of this work is to constrain the relation between the common estimators of the variability amplitude ( i.e.\, fractional variability and normalised excess variance)\, calculated in different energy bands\, with the physical and accretion properties of AGN such as the black hole masses of the central supermassive black hole (known for all the sources of the BASS sample from either broad Balmer lin es or reverberation mapping estimations) and Eddington ratios (estimated c ombining the black hole masses measurements with the estimates of the bolo metric luminosity derived from the BAT 14-150 keV luminosity). As expected from previous studies we find a strong anti-correlation between the exces s variance and the black hole mass. We do not find correlation between the excess variance and the Eddington ratio but we find a strong anti-correla tion with the 2-10 keV luminosity\, which disappears when we removed the d ependence of the excess variance on the black hole mass. Exploring the rel ation of excess variance in different energy bands we found that the varia bility of the sources of our sample is mostly due to the flux variation of the primary continuum and/or of the reflection component\, at least on sc ale of 10ks. I will also show the comparison of the variability property o f the unobscured AGN of the BASS sample with the X-ray variability propert ies of a sample of 5 Super and Hyper-Eddington sources (1$\n\nhttps://indi co.unina.it/event/61/contributions/866/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/866/ END:VEVENT BEGIN:VEVENT SUMMARY:Exploring black hole scaling relations via the ensemble variabilit y of active galactic nuclei DTSTART;VALUE=DATE-TIME:20230626T153000Z DTEND;VALUE=DATE-TIME:20230626T154500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-864@cern.ch DESCRIPTION:Speakers: Antonis Georgakakis (NOA)\nOne of the most influenti al relations in extragalactic astrophysics is the one that links the stell ar-mass component of galaxies (Mstar) to the masses of the supermassive bl ack holes (MBH) at their centres. Observational constraints on the shape\, normalisation and redshift evolution of the Mstar-MBH relation provide im portant clues on the co-evolution of galaxies and their supermassive black -holes. Unfortunately\, measuring the Mstar-MBH relation\, particularly at higher redshifts\, is challenging and prone to systemics. In this contrib ution I will present a new method that provides a handle on the Mstar-MBH relation by modelling the ensemble variability of X-ray selected AGN sampl es. A key ingredient of the method is the modelling strategy that links\, for the first time\, the demographics of AGN to the physics of the stochas tic flux variations of accretion flows and allows the interpretation of th e variability properties of AGN populations. I will demonstrate the predic tive power of the model by comparing in a forward manner with observationa l measurements of the ensemble excess variance of X-ray AGN in the Chandra Deep Field South. I will also discuss future prospects for joint constrai nts on both models of AGN variability and the Mstar-MBH relation as a func tion of redshift.\n\nhttps://indico.unina.it/event/61/contributions/864/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/864/ END:VEVENT BEGIN:VEVENT SUMMARY:The universal shape of the X-ray variability power spectrum of AGN up to z ∼ 3 DTSTART;VALUE=DATE-TIME:20230626T151500Z DTEND;VALUE=DATE-TIME:20230626T153000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-867@cern.ch DESCRIPTION:Speakers: Maurizio Paolillo (Università di Napoli Federico II )\nWe present a study of the ensemble X-ray variability of Active Galactic Nuclei (AGN) over a large range of timescales (20 ks ≤ T ≤ 14 yrs)\, redshift (0 ≤ z ≲ 3)\, luminosities ($10^{40} \\leq L_X \\leq 10^{46}\ \ \\mbox{erg s}^{−1}$) and black hole (BH) masses $10^6≤M_⊙≤10^9$) . Through the use of the "variance–frequency diagram"\, as a viable alte rnative to the power spectral density (PSD)\, we show that the data collec ted from archival observations and previous literature studies are consist ent with a universal PSD form which does not show evidence for systematic evolution of shape or amplitude with redshift or luminosity. We find new e vidence that the PSD bend\nfrequency depends on BH mass and\, possibly\, o n accretion rate. We will discuss the implications for current and future AGN population and cosmological studies\n\nhttps://indico.unina.it/event/6 1/contributions/867/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/867/ END:VEVENT BEGIN:VEVENT SUMMARY:Opportunities and challenges for spectral-timing models of AGN DTSTART;VALUE=DATE-TIME:20230626T141500Z DTEND;VALUE=DATE-TIME:20230626T143000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-874@cern.ch DESCRIPTION:Speakers: Andrew Young (University of Bristol)\nX-ray reverber ation mapping studies of AGN can\, in principle\, be used to measure the b lack hole mass and spin\, the accretion disc and corona geometries\, and t he ionisation state of the disc. We report on our efforts to fit the spect ra and time lags of a number of AGN\, but focus primarily on two sources\, 1H 0707-495 and IRAS 13224-3809. We can explain the low- and high-frequen cy lags\, find that an extended corona is required\, estimate the black ho le masses\, and find there are different correlations between parameters i n each object as their coronae change. However\, this model is slow to eva luate\, the parameter space had to be limited (e.g.\, fixed spin\; simplif ied geometry)\, it was difficult to characterise the error bars and degene racies in the model\, and the data were fairly noisy. We will discuss how new approaches to modelling and improved data will lead to a better unders tanding of the inner workings of AGN.\n\nhttps://indico.unina.it/event/61/ contributions/874/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/874/ END:VEVENT BEGIN:VEVENT SUMMARY:Review: X-ray variability of AGN DTSTART;VALUE=DATE-TIME:20230626T134500Z DTEND;VALUE=DATE-TIME:20230626T141500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-903@cern.ch DESCRIPTION:Speakers: Guglielmo Mastroserio ()\nSupermassive black holes p reserve information on the growth of the host galaxy and its dynamic evolu tion. Thus\, constraining their parameters is crucial to shed light on the ir formation and evolution. In recent years\, X-ray astronomy has undergon e a renaissance\, with several instruments that perform large observationa l campaigns and cover an extremely wide range of energy timescales to stud y Active Galactic Nuclei (AGN). The X-ray radiation produced by the closes t accreting matter to the black hole shows distortions due to the strong r elativistic effects. Proper modeling of these features constrains the syst em geometry and the interplay between the corona and the accretion disk. I will review the recent results of X-ray spectral timing analyses with an emphasis on the interpretation of the observations.\n\nhttps://indico.unin a.it/event/61/contributions/903/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/903/ END:VEVENT BEGIN:VEVENT SUMMARY:Revisiting the dust torus size - luminosity relationship in AGN ba sed on the mid-infrared reverberation mapping data DTSTART;VALUE=DATE-TIME:20230626T130000Z DTEND;VALUE=DATE-TIME:20230626T131500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-878@cern.ch DESCRIPTION:Speakers: Amit Kumar Mandal (Seoul National University\, Seoul )\nWe measured the dust torus  size of 86 quasars with bolometric AGN lu minosity in the range 10^43.4 to 10^46.4 erg/s  by determining the lag b etween the optical continuum emission obtained from ground-based optical s urveys\, i.e.\, CRTS\, ASAS-SN\, PTF and ZTF\, and the mid-infrared contin uum observed with the W1 and W2 bands from the Wide-field Infrared Survey Explorer (WISE) survey. By combining the new measurements with our re-anal yzed measurements of the sample in the literature\, we constrain the torus size - AGN luminosity relation over a large dynamic range of luminosities (i.e.\, 10^43.4 to 10^47.6 erg/s) with a slope of 0.31 and 0.32\, dependi ng on mid-infrared band W1 and W2-band\, respectively. We corrected the ac cretion disk contamination in the observed MIR light flux\, obtaining a sl ightly changed slope of 0.37 and 0.31 for W1 and W2-band lags\, respective ly. While the new slope is shallower than the value of 0.5 expected from thermal equilibrium model\, it is in good agreement with that obtained fro m the interferometric observations available in the literature. We also fo und wavelength dependent lags (from K to W1\, W2)\, suggesting a stratifie d structure of the dust torus\, such that emissions in different infrared wavelengths come from the different regions of the torus.\n\nhttps://indic o.unina.it/event/61/contributions/878/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/878/ END:VEVENT BEGIN:VEVENT SUMMARY:Searching for X-ray eclipses in NGC 6814 using dense optical/UV to X-ray monitoring with Swift DTSTART;VALUE=DATE-TIME:20230626T131500Z DTEND;VALUE=DATE-TIME:20230626T133000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-882@cern.ch DESCRIPTION:Speakers: Adam Gonzalez (Saint Mary's University)\nNGC 6814 is a nearby ($z = 0.005$) Seyfert 1.5 galaxy that we recently showed had und ergone a rapid X-ray occultation event during an *XMM-Newton* observation from 2016. The X-ray eclipse of high column ($N_{\\mathrm{H}} \\approx 10^ {23}~\\mathrm{cm}^{-2}$)\, mildly ionised ($\\log\\xi \\approx 1~\\mathrm{ erg~cm~s^{-1}}$) matter lasted ~45ks\, with ingress and egress each lastin g ~14ks\, revealing a partially covered X-ray region we estimated to be ~2 5 gravitational radii across. From August to November 2022 we observed NGC 6814 3-4 times per day with *Swift* to search for new X-ray eclipses to b etter understand the environment in this AGN. We present here a new analys is of the 2016 *XMM-Newton* data using X-ray colour-colour diagrams that r eveal an inhomogeneous\, clumpy obscurer\, which is likely embedded within an extended\, large scale structure based on simultaneous and long-term * Swift* coverage. Our 2022 *Swift* campaign reveals no new X-ray eclipses\, but offers a rich data set with which we conduct the first thermal reverb eration analysis of this AGN. We find highly correlated optical/UV to X-ra y variability that exhibits a significantly flatter time-lag spectrum than the predicted 4/3 power law relation of a standard X-ray illuminated accr etion disc. Furthermore\, we find that during the 2016 X-ray eclipse X-ray s de-correlate from optical/UV variation before resuming highly correlated broad band variability ~30 days later.\n\nhttps://indico.unina.it/event/6 1/contributions/882/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/882/ END:VEVENT BEGIN:VEVENT SUMMARY:Long and short term\, X-ray/optical/UV time-lags in AGN DTSTART;VALUE=DATE-TIME:20230626T100000Z DTEND;VALUE=DATE-TIME:20230626T101500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-876@cern.ch DESCRIPTION:Speakers: Iossif Papadakis ()\nRecent multi-wavelength surveys of a few AGN have given us the opportunity to constrain well the cross-co rrelation between the X-rays and the UV/optical variations in these object s. The variations in the UV lead the variations detected at longer wavelen gths in almost all cases where good quality light curves\, in many waveban ds\, exist. However\, there have been indications that the optical variati ons lead the UV variations on the longest sampled time scales in a few obj ects. This could indicate the presence of accretion rate variations which propagate inwards. We use well sampled\, long light curves of a few Seyfer t galaxies to compute the time lags on both long and short time scales. We will present the results regarding the dependence of the observed time-la gs on the probed time-scale\, and we will discuss possible constraints on various models for the observed optical/UV variations in AGN.\n\nhttps://i ndico.unina.it/event/61/contributions/876/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/876/ END:VEVENT BEGIN:VEVENT SUMMARY:Modelling thermal reverberation in active galactic nuclei DTSTART;VALUE=DATE-TIME:20230626T104500Z DTEND;VALUE=DATE-TIME:20230626T110000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-862@cern.ch DESCRIPTION:Speakers: Elias Kammoun (IRAP - CNRS)\nSeveral active galactic nuclei (AGN) show UV/optical variability lagging behind the X-ray emissio n by a few days. The simplest and most straightforward interpretation is t hat the variable X-ray flux from the corona illuminates the accretion disc below where it is partially reflected and observed as fast X-ray reverber ation signal\, and partially absorbed and thermalised in the disc\, which produces a slow UV and optical reverberation signal. Since the corona is t hought to be centrally located and very small compared to the accretion di sc\, it first illuminates the hottest inner parts of the accretion disc an d later on its colder further out areas. Thus one expects to see the origi nal X-ray fluctuations to be firstly followed by variations in the UV and then in the optical wavebands.\n\n\nIn this talk\, I will present our newl y developed full GR-ray-tracing code that computes the thermally reverbera ted UV/optical continuum responding to X-ray illumination by a compact cor ona. Our code considers the mutual interaction of the accretion disc and t he X–ray corona. I will discuss how the properties of the system (e.g.\, black hole spin\, accretion rate\, corona height\, etc.) affect the UV/op tical time lags. I will also present our results from modelling the observ ed lags obtained from long monitoring of bright local AGN.\n\nhttps://indi co.unina.it/event/61/contributions/862/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/862/ END:VEVENT BEGIN:VEVENT SUMMARY:The Optical-to-X-ray continuum variability of AGN: thermal fluctua tion rather than reprocessing? DTSTART;VALUE=DATE-TIME:20230626T103000Z DTEND;VALUE=DATE-TIME:20230626T104500Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-861@cern.ch DESCRIPTION:Speakers: Zhen-Yi Cai ()\nFrom optical to X-ray\, the variable continuum emissions of AGN are generally found to be correlated with vari ations at longer wavelengths lagging the shorter ones. Both the correlatio n and the lag-wavelength relation are usually understood within the widesp read X-ray reprocessing scenario. However\, both of them do not always pre serve and challenge the reprocessing scenario. In recent years\, we (Cai e t al. 2016\, 2018\, 2020) upgrade the inhomogeneous thermal fluctuation mo del proposed by Dexter & Agol (2011)\, by introducing a common larger-scal e fluctuation (as a result of the propagation and mixing of local fluctuat ions\, likely\, by magnetic fields allover the accretion disk) and suggest ing a new origin for the continuum lag (as a result of the differential re gression capability of local fluctuations responding to the large-scale fl uctuation). Now\, the new thermal fluctuation scenario can account for sev eral observational properties of AGN variability\, including the correlati on and lag across the X-ray/UV/optical and the timescale-dependent color v ariation\, and may shed new light on comprehending the UV/optical continuu m variations and the relation to X-ray for AGN.\n\nhttps://indico.unina.it /event/61/contributions/861/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/861/ END:VEVENT BEGIN:VEVENT SUMMARY:Probing Accretion Disk Structure with Long Lags in AGN Photometry DTSTART;VALUE=DATE-TIME:20230626T094500Z DTEND;VALUE=DATE-TIME:20230626T100000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-860@cern.ch DESCRIPTION:Speakers: Amy Secunda (Princeton University)\nI will discuss t he use of longer timescale “negative” lags\, where the variability in high frequency bands lags the corresponding variability at low frequency\, as a probe of accretion disk structure. Traditional reverberation mapping uses lags of variations in AGN photometry from high frequency to low freq uency wavebands on the light-crossing timescale which come from the reproc essing of light in different temperature regions of the disk. The long neg ative lag\, on the other hand\, is due to fluctuations in the outer part o f the UV/optical region of the disk that are accreted inward on the inflow timescale. Because the inflow rate also depends on disk properties\, unli ke the speed of light\, these long lags can provide additional information about disk structure. Standard disk models predict the inflow timescale i s on the order of hundreds of years. However\, recent 3D radiation magneto hydrodynamic simulations of AGN disks and analysis of high-cadence\, long baseline observations of Fairall 9 suggest that in the UV/optical region o f the disk\, the inflow timescale can be on the order of only 100 days\, n ot years. This much shorter lag timescale would make the detection of long lags possible with long baseline observations from instruments such as SW IFT or Vera C. Rubin Observatory. I will outline the underlying theory of these long lags\, show results from 3D radiation magnetohydrodynamic simul ations of disk models beyond the standard disk model\, and also present so me candidate long lags.\n\nhttps://indico.unina.it/event/61/contributions/ 860/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/860/ END:VEVENT BEGIN:VEVENT SUMMARY:Looking beyond the lamppost: a new method of understanding AGN con tinuum variability DTSTART;VALUE=DATE-TIME:20230626T101500Z DTEND;VALUE=DATE-TIME:20230626T103000Z DTSTAMP;VALUE=DATE-TIME:20260417T191641Z UID:indico-contribution-61-859@cern.ch DESCRIPTION:Speakers: Jack Neustadt (The Ohio State University)\nThe varia bility of Active Galactic Nuclei (AGNs) has been studied for decades\, wit h the UV/optical continuum observed to stochastically fluctuate at the 10% level over timescales of weeks to months. Fundamentally\, this variabilit y should be driven by temperature fluctuations in the accretion disc surro unding the central black hole. Where multiband lightcurves are available \, the variability is similar in all bands\, but the bluer wavelengths var y earlier than the redder wavelengths with delays typical of the light tra vel time across the disc. These observations have led to the commonly use d "lamppost" model\, where central luminosity fluctuations - typically lin ked with X-ray emission - irradiate the disc to drive the UV/optical varia bility. However\, it seems unlikely that this is the only source of vari ability in the disc. We introduce a new approach to understanding disc va riability where we invert the multiband UV/optical lightcurves of AGNs int o “maps” of the disc resolved in time and in radius under the assumpti on of axisymmetry. In addition to a lamppost "signal"\, we see strong ev idence for small amplitude\, slow-moving temperature fluctuations. We sugg est that these fluctuations dominate AGN variability on long timescales\, a hypothesis that will be tested by Rubin/LSST in the near future. This n ew method for understanding disc variability can also be used to probe oth er issues\, such as the degree to which unrecognized emission from the bro ad line region (BLR) contaminates continuum lightcurves.\n\nhttps://indico .unina.it/event/61/contributions/859/ LOCATION:Centro Congressi Federico II Aula Magna URL:https://indico.unina.it/event/61/contributions/859/ END:VEVENT END:VCALENDAR