The rate of stellar tidal disruption flares from SDSS data

¹ Department of Astrophysics/IMAPP, Radboud University, PO Box 9010, 6500 GL Nijmegen, The Netherlands
² Center for Cosmology and Particle Physics, New York University, NY 10003, USA
³ Department of Physics, New York University, NY 10003, USA

^a e-mail: s.vanvelzen@astro.ru.nl

Abstract

We have searched for flares due to the tidal disruption of stars by supermassive black holes in archival Sloan Digital Sky Survey (SDSS) multi-epoch imaging data. Our pipeline takes advantage of the excellent astrometry of SDSS to separate nuclear flares from supernovae. The 10 year baseline and the high cadence of the observations facilitate a clear-cut identification of variable active galactic nuclei. We found 186 nuclear flares, of which two are strong stellar tidal disruption flare (TDF) candidates. To compute the rate of these events, we simulated our entire pipeline to obtain the efficiency of detection for a given light curve. We compute a model-independent upper limit to the TDF rate of Ṅ < 3 × 10⁻⁴ yr⁻¹galaxy⁻¹ (90% CL). Using a simple model to extrapolate the observed light curve forward and backward in time, we find our best-estimate of the rate: Ṅ = 3_-3⁺⁵ × 10⁻⁵ yr⁻¹galaxy⁻¹.