Abstract
The tidal disruption of stars by supermassive black holes produces luminous soft X-ray accretion flares in otherwise inactive galaxies. First events have been discovered in X-rays with the ROSAT observatory, and have more recently been detected with XMM-Newton, Chandra and Swift, and at other wavelengths. In X-rays, they typically appear as very soft, exceptionally luminous outbursts of radiation, which decline consistent with L ∝ t −5/3 on the timescale of months to years. They reach total amplitudes of decline up to factors 1000-6000 more than a decade after their initial high-states, and in low-state, their host galaxies are essentially X-ray inactive, optically inactive, and radio inactive. X-ray luminous tidal disruption events (TDEs) represent a powerful new probe of accretion physics near the event horizon, and of relativistic effects. TDEs offer a new way of estimating black hole spin, and they are signposts of supermassive binary black holes and recoiling black holes. Once discovered in the thousands in upcoming sky surveys, their rates will probe stellar dynamics in distant galaxies, and they will uncover the - so far elusive - population of intermediate mass black holes in the universe, if they do exist. Further, the reprocessing of the flare into IR, optical and UV emission lines provides us with multiple new diagnostics of the properties of any gaseous material in the vicinity of the black hole (including the disrupted star itself) and in the host galaxy. First candidate events of this kind have been reported recently.
Highlights
The tidal disruption, and subsequent accretion, of a star by a supermassive black hole (SMBH) produces a luminous flare of electromagnetic radiation, visible out to large cosmic distances (Luminet 1985, Rees 1988)
The tidal disruption of stars by supermassive black holes produces luminous soft X-ray accretion flares in otherwise inactive galaxies
First events have been discovered in X-rays with the ROSAT observatory, and have more recently been detected with XMM-Newton, Chandra and Swift, and at other wavelengths
Summary
The tidal disruption, and subsequent accretion, of a star by a supermassive black hole (SMBH) produces a luminous flare of electromagnetic radiation, visible out to large cosmic distances (Luminet 1985, Rees 1988). Events have initially been discovered in the form of luminous X-ray flares from otherwise non-active galaxies during the ROSAT all-sky survey (e.g., Komossa & Bade 1999), providing us with a new method of unveiling the dormant SMBH population in the universe, and studying accretion processes and the immediate environment of SMBHs. More recently, events from otherwise quiescent galaxies have been seen in the UV, optical, and radio regime, and they continue to be detected in X-rays. A star approaching a SMBH is subject to strong tidal forces exerted by the black hole. Once these exceed the self-gravity of the star, the star is disrupted (Hills 1975). Observations of UV and optical TDEs1 will be reviewed by Gezari (these proceedings)
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