Astronomy Colloquium Speaker Calendar

Stars near our own Galactic Center are going around a supermassive black hole with orbital periods as short as a decade. Recent observations unveiled a new class of mysterious sources showing periodic bursts of X-ray emission at the centers of some distant galaxies. Different sources show a wide range of recurrence times from a few hours to days. In this talk, I will argue that these X-ray bursts are produced by stars on extremely close orbits around supermassive black holes. In each orbit, the star interacts with the gas in an accretion disk. This causes the outer layers of the star to expand and then get stripped by the black hole's tidal forces. These stars dance for only 100 years before they are eaten up. A mechanism that efficiently brings stars to such close orbits will be discussed.