Professor Yue Shen (Department of Astronomy, University of Illinois at Urbana-Champaign)
"The final parsec: time-domain exploration of the inner regions of quasars"
時間/地點： 2018-12-21 15:00 [S4-1013]
The spatially-unresolved sub-parsec region of quasars (rapidly accreting
supermassive black holes) is a dynamic environment where the most
important processes related to BH accretion and feedback are taking
place. Studying this region observationally, however, requires somewhat
different approaches that are not hurdled by the spatial resolution
requirement. A hallmark characteristic of quasars is their ubiquitous
variability over a wide range of wavelengths and timescales from
intra-day to decades, which provides unique and critical constraints on
the structure, dynamics, and radiative processes in the innermost
emitting regions of accreting SMBHs that are otherwise difficult to
probe. I will give a brief overview on variability studies to understand
the inner structures of quasars, with several examples such as the
measurement of the sizes of the accretion disk and the gaseous
broad-line region with light echos, and the discovery and
characterization of extreme variability events that challenge current
accretion theories. Finally I will discuss the prospects of advancing
quasar science in the upcoming time-domain era of LSST.
Professor Xin Liu (Department of Astronomy, University of Illinois at Urbana-Champaign)
"Finding low-frequency gravitational wave sirens in the electromagnetic sky"
時間/地點： 2018-12-21 14:00 [S4-1013]
Binary supermassive black holes are expected to be common from galaxy mergers. Their final coalescence is believed to be the loudest gravitational wave siren in the universe, yet no confirmed binary is known to be close enough so that it would efficiently emit gravitational waves to merge within the age of the universe. Over the past few years, systematic searches using synoptic surveys based on active galactic nucleus variability have started to yield a sample of intriguing candidates. I will review the results from these searches and discuss future prospects to confirm systems that are directly emitting low-frequency gravitational waves.
Dr. Cheng-Ling Kuo (Institute of Space Science, NCU)