报告题目：The Gamma-ray Afterglows of Tidal Disruption Events

报 告 人：陈弦 (Pontificia Universidad Católica de Chile)

报告时间：2015年10月27日（周二）下午3：00

报告地点：蒙民伟科技南楼S727

报告摘要：Tidal disruption event (TDE) — the incident in which a star becomes too close to a supermassive black hole (SMBH) so that it is tidally disrupted — provides an effective means of revealing the otherwise invisible SMBHs in normal galaxies. Conventionally, the search of TDE is carried out in UV and soft X-ray wavebands, where most of the emission is coming from, but photons in these bands are subject to extinction and this contributes a major uncertainty in the TDE research. Recently, it is realized that the interaction between the debris of a disrupted star with the surrounding ISM inevitably produces a large amount of cosmic rays, and eventually results in a long-lasting gamma-ray glow as the cosmic rays propagate in the host galaxy. Such a gamma-ray signature provides an alternative tool to probe TDE, which is less affected by extinction. In this talk, I will outline the properties of this gamma-ray signature. In particular, I will present the results from our recent studies of the interaction of stellar debris with molecular clouds, which are expect to exist in large amount close to SMBHs. The subsequent gamma-ray emission is much stronger than what is expected in the case of a smooth ISM, and such a gamma-ray source potentially could be detected by Fermi and H.E.S.S., and mostly likely by the future Cherenkov Telescopes Array (CTA) out to a distance of tens of Mpc. Our work also has profound implications for the search of other gamma-ray sources, such as starbursts, pulsars, and dark-matter annihilation, which will be briefly discussed towards the end of the talk.