Optical discovery of probable stellar tidal discruption flares
Number of pages
Faculty of Science (FNWI)
Anton Pannekoek Institute for Astronomy (API)
Using archival Sloan Digital Sky Survey (SDSS) multi-epoch imaging data (Stripe 82), we have searched for the tidal disruption
of stars by supermassive black holes in non-active galaxies. Two candidate tidal disruption events (TDEs) are identified.
The TDE flares have optical blackbody temperatures of 2 × 104 K and observed peak luminosities of Mg = -18.3 and -20.4 (νL
ν = 5 × 1042, 4 × 1043 erg s-1, in the rest frame); their cooling rates are very low, qualitatively consistent with expectations
for tidal disruption flares. The properties of the TDE candidates are examined using (1) SDSS imaging to compare them to other
flares observed in the search, (2) UV emission measured by GALEX, and (3) spectra of the hosts and of one of the flares. Our
pipeline excludes optically identifiable AGN hosts, and our variability monitoring over nine years provides strong evidence
that these are not flares in hidden AGNs. The spectra and color evolution of the flares are unlike any SN observed to date,
their strong late-time UV emission is particularly distinctive, and they are nuclear at high resolution arguing against these
being first cases of a previously unobserved class of SNe or more extreme examples of known SN types. Taken together, the
observed properties are difficult to reconcile with an SN or an AGN-flare explanation, although an entirely new process specific
to the inner few hundred parsecs of non-active galaxies cannot be excluded. Based on our observed rate, we infer that hundreds
or thousands of TDEs will be present in current and next-generation optical synoptic surveys. Using the approach outlined
here, a TDE candidate sample with O(1) purity can be selected using geometric resolution and host and flare color alone, demonstrating
that a campaign to create a large sample of TDEs, with immediate and detailed multi-wavelength follow-up, is feasible. A by-product
of this work is quantification of the power spectrum of extreme flares in AGNs.
go to publisher's site
If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let
the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible
and/or remove it from the website. Please Ask the Library, or send a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands.
You will be contacted as soon as possible.