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A DECAM SEARCH FOR AN OPTICAL COUNTERPART TO THE LIGO GRAVITATIONAL-WAVE EVENT GW151226

Cowperthwaite, PS; Berger, E; Soares-Santos, M; Annis, J; Brout, D; Brown, DA; Buckley-Geer, E; ... Weller, J; + view all (2016) A DECAM SEARCH FOR AN OPTICAL COUNTERPART TO THE LIGO GRAVITATIONAL-WAVE EVENT GW151226. ASTROPHYSICAL JOURNAL LETTERS , 826 (2) 10.3847/2041-8205/826/2/L29. Green open access

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Abstract

We report the results of a Dark Energy Camera optical follow-up of the gravitational-wave (GW) event GW151226, discovered by the Advanced Laser Interferometer Gravitational-wave Observatory detectors. Our observations cover 28.8 deg2 of the localization region in the i and z bands (containing 3% of the BAYESTAR localization probability), starting 10 hr after the event was announced and spanning four epochs at 2–24 days after the GW detection. We achieve $5\sigma $ point-source limiting magnitudes of $i\approx 21.7$ and $z\approx 21.5$, with a scatter of 0.4 mag, in our difference images. Given the two-day delay, we search this area for a rapidly declining optical counterpart with $\gtrsim 3\sigma $ significance steady decline between the first and final observations. We recover four sources that pass our selection criteria, of which three are cataloged active galactic nuclei. The fourth source is offset by 5.8 arcsec from the center of a galaxy at a distance of 187 Mpc, exhibits a rapid decline by 0.5 mag over 4 days, and has a red color of $i-z\approx 0.3$ mag. These properties could satisfy a set of cuts designed to identify kilonovae. However, this source was detected several times, starting 94 days prior to GW151226, in the Pan-STARRS Survey for Transients (dubbed as PS15cdi) and is therefore unrelated to the GW event. Given its long-term behavior, PS15cdi is likely a Type IIP supernova that transitioned out of its plateau phase during our observations, mimicking a kilonova-like behavior. We comment on the implications of this detection for contamination in future optical follow-up observations.

Type: Article
Title: A DECAM SEARCH FOR AN OPTICAL COUNTERPART TO THE LIGO GRAVITATIONAL-WAVE EVENT GW151226
Open access status: An open access version is available from UCL Discovery
DOI: 10.3847/2041-8205/826/2/L29
Publisher version: http://dx.doi.org/10.3847/2041-8205/826/2/L29
Additional information: © 2016. The American Astronomical Society.
Keywords: Science & Technology, Physical Sciences, Astronomy & Astrophysics, binaries: close, catalogs, gravitational waves, stars: neutron, surveys, ENERGY CAMERA SEARCH, SUPERNOVA RATES, IA SUPERNOVAE, FOLLOW-UP, GW150914, CURVES, PHOTOMETRY, PAN-STARRS1, AFTERGLOWS, LMC
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
URI: https://discovery-pp.ucl.ac.uk/id/eprint/1540185
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