Copy of Tidal Disruption Events: A New Black Hole Census

Описание: Tidal disruption events, or TDEs, occur when stars pass too close to massive black holes (MBHs) and are spaghettified by tidal forces. The ensuing fallback of stellar debris powers a luminous flare brighter than most supernovae, with most of the luminosity emerging as quasi-thermal optical, UV, and soft X-rays. These transients have great potential to measure the demographics of MBHs in the Universe, especially at the uncertain bottom end of the MBH mass function: they preferentially occur in the smallest nucleated galaxies, they are visible to cosmological distances, and their light curves are governed by just a handful of free parameters. Furthermore, upcoming advances in time domain astronomy will turn TDE discovery from an artisanal into an industrial process: while less than 100 TDEs are known today, the upcoming LSST optical survey and ULTRASAT UV survey will each find thousands per year. In this talk, I will discuss the potential of TDEs to resolve long-standing questions on MBH demographics, origins, and evolution, focusing both on what can already be done today with techniques such as X-ray continuum fitting, and on the theoretical challenges that must be resolved before making further progress in optical/UV modeling. With an emphasis on recent progress in ab initio simulations, I will review the key theoretical questions concerning TDE flares: how does the debris circularize into an accretion flow? And what is the power source and geometry of the optical/UV emission? I will argue that the answer to these long-standing questions are finally emerging, and that observed optical/UV light curves can now be modeled from first principles.