IAASARS Seminar: Dr. Panos Charalampopoulos - Spectra of black-hole-tidally disrupted stars скачать в хорошем качестве

IAASARS Seminar: Dr. Panos Charalampopoulos - Spectra of black-hole-tidally disrupted stars

____________________________________________________________________________________________________________________________________________________________ Wednesday, December 18 15 at 12:00 EET Dr. Panos Charalampopoulos (University of Turku, Finland) Title: How do the spectra of stars that are tidally disrupted by supermassive black holes look like? (Almost) two decades of discoveries and questions Abstract: Tidal disruption events (TDEs) occur when a star gets too close to a supermassive black hole (SMBH) and is ripped apart by the black hole’s gravitational field, resulting in a luminous, panchromatic, transient flare. By their very nature, TDEs are a unique tool for probing SMBHs and their existence was predicted by theorists since the 80s. The first candidates were discovered in the X-ray regime in the late 90s and only at 2006 the detections of potential candidates in the optical and UV began. Since then, thanks to the rapid development of dedicated large surveys for time-domain astronomy, the number of detected candidates has surpassed 100. However, even though TDEs are now routinely discovered by surveys, the physics underlying the emission mechanism that powers them has remained elusive. Spectroscopically, the first optical spectrum of a TDE was obtained in 2007; it displayed broad emission features around Hα, Hβ and He II λ4686 and, to-date, these remain the most characteristic spectral features for a nuclear transient to be classified as a TDE. Nevertheless, since then we have come to understand that the spectral properties of optical/UV TDEs show a large diversity, potential evolution with time and, occasionally, unique features that are puzzling and challenging to understand. In this talk, I will attempt to give a concise review of the spectral properties of optical/UV TDEs, and discuss potential links between those properties and the geometrical structures, as well as their (still) elusive emission mechanism. _____________________________________________________________________________________________________________________________________________________________