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第1476回 天文学教室談話会

日時

2016年11月16日(水) 15:00

場所

合同C棟多目的室

講演者

Xiaoyang Chen

題目

Analyses on Asymmetric Variability of AGN

要旨


Aperiodic optical / ultraviolet variability is a significant property of active galactic nuclei (AGN), but its physical origin is still unclear. Variability asymmetry describes whether a light curve favors the shape of rapid rise and gradual decay, i.e., positive asymmetry, or the shape of gradual rise and rapid decay, i.e., negative asymmetry. There are only a few observational / theoretical works in the literature which study the variability asymmetry of AGN. Studying the asymmetry in variations could provide independent constraints on physical models for AGN variability. Through Monte Carlo simulations, Kawaguchi et al. (1998) showed that the disk instability model produces negative asymmetry, while the starburst model, which attributes the optical variations to the random superposition of supernovae in the nuclear starburst region, yields a contrary asymmetry. The high-quality light curves from the Kepler space telescope make it possible to analyze the optical variability of AGN with unprecedented time resolution. In this work, we use Kepler observations of 19 sources to perform analyses of the variability asymmetry of AGN. After deducting the bias toward high-frequency variability asymmetry caused by poorly sampled long-term variations, individual sources show no evidence of asymmetry at timescales of 1 ~ 20 days and there is no general trend toward positive or negative asymmetry over the whole sample. Our results indicate that short-term optical variations in AGN are highly symmetric.

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【The Colloquium Committee in 2016】
Kenji Toma (toma<at>astr.tohoku.ac.jp)
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