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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:20260818T023830Z
UID:indico-contribution-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/
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