Sifting for Sapphires: Systematic Selection of Tidal Disruption Events in iPTF

October 2018 • 2018ApJS..238...15H

Authors • Hung, T. • Gezari, S. • Cenko, S. B. • van Velzen, S. • Blagorodnova, N. • Yan, Lin • Kulkarni, S. R. • Lunnan, R. • Kupfer, T. • Leloudas, G. • Kong, A. K. H. • Nugent, P. E. • Fremling, C. • Laher, Russ R. • Masci, F. J. • Cao, Y. • Roy, R. • Petrushevska, T.

Abstract • We present results from a systematic selection of tidal disruption events (TDEs) in a wide-area (4800 deg²), g+R band, Intermediate Palomar Transient Factory experiment. Our selection targets typical optically selected TDEs: bright (>60% flux increase) and blue transients residing in the centers of red galaxies. Using photometric selection criteria to down-select from a total of 493 nuclear transients to a sample of 26 sources, we then use follow-up UV imaging with the Neil Gehrels Swift Telescope, ground-based optical spectroscopy, and light curve fitting to classify them as 14 Type Ia supernovae (SNe Ia), 9 highly variable active galactic nuclei (AGNs), 2 confirmed TDEs, and 1 potential core-collapse supernova. We find it possible to filter AGNs by employing a more stringent transient color cut (g - r < -0.2 mag); further, UV imaging is the best discriminator for filtering SNe, since SNe Ia can appear as blue, optically, as TDEs in their early phases. However, when UV-optical color is unavailable, higher-precision astrometry can also effectively reduce SNe contamination in the optical. Our most stringent optical photometric selection criteria yields a 4.5:1 contamination rate, allowing for a manageable number of TDE candidates for complete spectroscopic follow-up and real-time classification in the Zwicky Transient Facility era. We measure a TDE per galaxy rate of {1.7}_-1.3^+2.9× {10}^-4 {gal}}^-1 {yr}}^-1 (90% CL in Poisson statistics). This does not account for TDEs outside our selection criteria, and thus may not reflect the total TDE population, which is yet to be fully mapped.

Links

• PREPRINT http://arxiv.org/abs/1712.04936
• NED https://ned.ipac.caltech.edu/uri/NED::InRefcode/2018ApJS..238...15H
• ELECTR https://doi.org/10.3847%2F1538-4365%2Faad8b1
• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2018ApJS..238...15H
• PDF https://iopscience.iop.org/article/10.3847/1538-4365/aad8b1/pdf
• PDF https://stacks.iop.org/0067-0049/238/15/pdf
• DATA http://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/biblink.pl?code=2018ApJS..238...15H
• DATA https://nxsa.esac.esa.int/nxsa-web/#bibcode=2018ApJS..238...15H