Measurement of the rate of stellar tidal disruption flares

Sjoert Van Velzen, Glennys R. Farrar

    Research output: Contribution to journalArticle

    Abstract

    We report an observational estimate of the rate of stellar tidal disruption flares (TDFs) in inactive galaxies based on a successful search for these events among transients in galaxies using archival Sloan Digital Sky Survey (SDSS) multi-epoch imaging data (Stripe 82). This search yielded 186 nuclear flares in galaxies, 2 of which are excellent TDF candidates. Because of the systematic nature of the search, the very large number of galaxies, the long time of observation, and the fact that non-TDFs were excluded without resorting to assumptions about TDF characteristics, this study provides an unparalleled opportunity to measure the TDF rate. To compute the rate of optical stellar tidal disruption events, we simulate our entire pipeline to obtain the efficiency of detection. The rate depends on the light curves of TDFs, which are presently still poorly constrained. Using only the observed part of the SDSS light curves gives a model-independent upper limit to the optical TDF rate, Ṅ < 2 × 10-4 yr-1 galaxy-1 (90% CL), under the assumption that the SDSS TDFs are representative examples.We develop three empirical models of the light curves based on the two SDSS light curves and two more recent and better-sampled Pan-STARRS TDF light curves, leading to our best estimate of the rate: ṄTDF = (1.5-2.0) -1.3 +2.7 ×10-5 yr-1 galaxy-1. We explore the modeling uncertainties by considering two theoretically motivated light curve models, as well as two different relationships between black hole mass and galaxy luminosity, and two different treatments of the cutoff in the visibility of TDFs at large MBH. From this we conclude that these sources of uncertainty are not significantly larger than the statistical ones. Our results are applicable for galaxies hosting black holes with mass in the range of a few 106-10 8M⊙, and translates to a volumetric TDF rate of (4-8)×10-8±0.4 yr-1 Mpc-3, with the statistical uncertainty in the exponent.

    Original languageEnglish (US)
    Article number53
    JournalAstrophysical Journal
    Volume792
    Issue number1
    DOIs
    StatePublished - Sep 1 2014

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    flares
    light curve
    galaxies
    rate
    visibility
    estimates
    modeling
    cut-off
    luminosity
    time measurement
    exponents

    Keywords

    • black hole physics
    • galaxies: kinematics and dynamics
    • galaxies: nuclei
    • quasars: supermassive black holes

    ASJC Scopus subject areas

    • Space and Planetary Science
    • Astronomy and Astrophysics

    Cite this

    Measurement of the rate of stellar tidal disruption flares. / Van Velzen, Sjoert; Farrar, Glennys R.

    In: Astrophysical Journal, Vol. 792, No. 1, 53, 01.09.2014.

    Research output: Contribution to journalArticle

    Van Velzen, Sjoert ; Farrar, Glennys R. / Measurement of the rate of stellar tidal disruption flares. In: Astrophysical Journal. 2014 ; Vol. 792, No. 1.
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