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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:20260519T010519Z
UID:indico-contribution-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/
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