The Needle in the 100 deg^2 Haystack: Uncovering Afterglows of Fermi GRBs with the Palomar Transient Factory

Creators: Singer, Leo P.; Weinstein, Alan; Perley, Daniel A.; Cao, Yi; Kulkarni, S. R.; Masci, Frank; Kasliwal, M. M.

Abstract

The Fermi Gamma-ray Space Telescope has greatly expanded the number and energy window of observations of gamma-ray bursts (GRBs). However, the coarse localizations of tens to a hundred square degrees provided by the Fermi GRB Monitor instrument have posed a formidable obstacle to locating the bursts' host galaxies, measuring their redshifts, and tracking their panchromatic afterglows. We have built a target-of-opportunity mode for the intermediate Palomar Transient Factory in order to perform targeted searches for Fermi afterglows. Here, we present the results of one year of this program: 8 afterglow discoveries out of 35 searches. Two of the bursts with detected afterglows (GRBs 130702A and 140606B) were at low redshift (z = 0.145 and 0.384, respectively) and had spectroscopically confirmed broad-line Type Ic supernovae. We present our broadband follow-up including spectroscopy as well as X-ray, UV, optical, millimeter, and radio observations. We study possible selection effects in the context of the total Fermi and Swift GRB samples. We identify one new outlier on the Amati relation. We find that two bursts are consistent with a mildly relativistic shock breaking out from the progenitor star rather than the ultra-relativistic internal shock mechanism that powers standard cosmological bursts. Finally, in the context of the Zwicky Transient Facility, we discuss how we will continue to expand this effort to find optical counterparts of binary neutron star mergers that may soon be detected by Advanced LIGO and Virgo.

Additional Information

© 2015 American Astronomical Society. Received 2015 January 2; accepted 2015 February 28; published 2015 June 8. L.P.S. thanks generous support from the National Science Foundation (NSF) in the form of a Graduate Research Fellowship. The National Radio Astronomy Observatory is a facility of the NSF operated under cooperative agreement by Associated Universities, Inc. This paper is based on observations obtained with the Palomar 48 inch Oschin telescope and the Palomar 60 inch telescope at the Palomar Observatory as part of the Intermediate Palomar Transient Factory project, a scientific collaboration among the California Institute of Technology, Los Alamos National Laboratory, the University of Wisconsin, Milwaukee, the Oskar Klein Center, the Weizmann Institute of Science, the TANGO Program of the University System of Taiwan, and the Kavli Institute for the Physics and Mathematics of the Universe. The present work is partly funded by Swift Guest Investigator Program Cycle 9 award 10522 (NASA grant NNX14AC24G) and Cycle 10 award 10553 (NASA grant NNX14AI99G). Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA; the Observatory was made possible by the generous financial support of the W.M. Keck Foundation. We thank Thomas Krühler for reducing the X-shooter spectrum of GRB 131011A/iPTF13dsw. We thank the staff of the Mullard Radio Astronomy Observatory for their invaluable assistance in the operation of AMI. G.E.A., R.P.F., and T.D.S. acknowledge the support of the European Research Council Advanced Grant 267697, "4 Pi Sky: Extreme Astrophysics with Revolutionary Radio Telescopes." Support for CARMA construction was derived from the Gordon and Betty Moore Foundation; the Kenneth T. and Eileen L. Norris Foundation; the James S. McDonnell Foundation; the Associates of the California Institute of Technology; the University of Chicago; the states of California, Illinois, and Maryland; and the NSF. Ongoing CARMA development and operations are supported by the NSF under a cooperative agreement and by the CARMA partner universities. These results made use of Lowell Observatory's DCT. Lowell operates the DCT in partnership with Boston University, Northern Arizona University, the University of Maryland, and the University of Toledo. Partial support of the DCT was provided by Discovery Communications. LMI was built by Lowell Observatory using funds from the NSF (AST- 1005313). This work is partly based on observations made with GTC, at the Roque de los Muchachos Observatory (La Palma, Spain). The research activity of A.d.U.P., C.T., and J.G. is supported by Spanish research project AYA2012-39362-C02-02. A.d.U.P. acknowledges support by the European Commission under the Marie Curie Career Integration Grant programme (FP7-PEOPLE-2012-CIG 322307). A portion of this work was carried out at the Jet Propulsion Laboratory under a Research and Technology Development Grant, under contract with NASA. US Government Support Acknowledged. K.H. acknowledges support for the IPN under the following NASA grants: NNX07AR71G, NNX13AP09G, NNX11AP96G, and NNX13AI54G. The Konus-Wind experiment is partially supported by a Russian Space Agency contract and RFBR grants 15-02-00532 and 13-02-12017-ofi-m. IRAF is distributed by the National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA) under cooperative agreement with the NSF. This research has made use of data, software, and/or web tools obtained from HEASARC, a service of the Astrophysics Science Division at NASA/GSFC and of the Smithsonian Astrophysical Observatory's High Energy Astrophysics Division. This research has made use of NED, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester including the Swift XRT GRB catalog and light-curve repository (Evans et al. 2007, 2009; Goad et al. 2007). This research made use of Astropy49 (Robitaille et al. 2013), a community developed core Python package for Astronomy. Some of the results in this paper have been derived using HEALPix (Górski et al. 2005). Facilities: Fermi (GBM, LAT), PO:1.2 m (CFH12k), PO:1.5 m, Hale (DBSP), Gemini:Gillett (GMOS), Gemini: South (GMOS), EVLA, CARMA, Swift (XRT, UVOT), Keck:I (LRIS), Keck:II (DEIMOS), NOT (ALFOSC), HCT, AMI, VLT: Melipal (X-shooter), INTEGRAL(SPI-ACS), Odyssey (HEND), MESSENGER (GRNS), WIND (Konus)

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