Astronomy Colloquium - Nicholas Stone
- Nicholas Stone
Tidal disruption flares (TDFs) arise when stars pass too close to supermassive black holes (SMBHs) in galactic nuclei. These rare events occur roughly once every 10,000 years in typical galactic nuclei, but produce powerful multiwavelength transients brighter than typical Type I and II supernovae. Our current sample of TDFs consists of a modest few dozen events, but has already produced a number of observational surprises not predicted by theory. I will discuss my own work to understand two of these surprises. First, an order unity fraction of TDF hosts are rare post-starburst (or “E+A”) galaxies, which make up ~0.2% of all low redshift galaxies. Clearly, something very unusual is at play in the central parsecs of this galaxy subtype; a popular explanation is the presence of unresolved SMBH binaries, which may enhance the TDF rate. My own theoretical work and analysis of HST archival data suggests a different explanation, one connected to highly overdense nuclear stellar systems formed in the starburst that created the E+A galaxy. Second, the superficially low fraction of jetted, or relativistic, TDFs carries significant implications for SMBH jet launching physics. I will discuss my recent work confirming a dearth of highly luminous jets in observed thermal TDFs, and its bearing on the search for “hidden variables” controlling SMBH jet power. I will conclude by briefly discussing ways in which TDFs will probe quiescent SMBH demography in the LSST era, when thousands will be discovered every year.