SHAO Astrophysics Colloquia

Title: The UV/Optical Variation in Active Galactic Nuclei

Speaker: Prof. Junxian Wang (Univ. of Science and Technology of China)

Time: 3:00 PM, June 22 (Thursday)

Location: Lecture Hall, 3rd floor

Abstract:  Stochastic variation is one of the most prominent characteristics of AGNs. The UV/optical emission, which is believed from the accretion disk, is variable on timescales of days to years，the origin of which remains unclear for decades. I will present our recent works in the field, aimed to explore the origin of the variations and address the following key questions:

1)  Why AGNs appear bluer when they brighten?

2)  Why the variations in various UV/optical bands are well coordinated，  with the short wavelength variations leading the long wavelength ones?

3)  Which factors control the variation amplitude?

I will also show that variations provide a unique probe to spatially “resolve” the accretion disc. With this tool, we find the inner accretion disc in radio loud quasars clearly differ from that in radio quiet ones, offering an exciting clue to jet launching in quasars.