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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:20260306T084438Z
UID:indico-contribution-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/
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