A Tale of Two Transients: GW 170104 and GRB 170105A

Creators: Bhalerao, V.; Kasliwal, M. M.; Adams, S. M.; Blagorodnova, N.; Jencson, J.; Kupfer, T.; Vedantham, H.

Abstract

We present multi-wavelength follow-up campaigns by the AstroSat CZTI and GROWTH collaborations in search of an electromagnetic counterpart to the gravitational wave event GW 170104. At the time of the GW 170104 trigger, the AstroSat CZTI field of view covered 50.3% of the sky localization. We do not detect any hard X-ray (>100 keV) signal at this time, and place an upper limit of ≈4.5 x 10^(-7) erg cm^(-2) s^(-1), for a 1 s timescale. Separately, the ATLAS survey reported a rapidly fading optical source dubbed ATLAS17aeu in the error circle of GW 170104. Our panchromatic investigation of ATLAS17aeu shows that it is the afterglow of an unrelated long, soft GRB 170105A, with only a fortuitous spatial coincidence with GW 170104. We then discuss the properties of this transient in the context of standard long GRB afterglow models.

Additional Information

© 2017 The American Astronomical Society. Received 2017 June 7; revised 2017 July 19; accepted 2017 July 20; published 2017 August 22. The CZT Imager is built by a consortium of Institutes across India. The Tata Institute of Fundamental Research, Mumbai, led the effort with instrument design and development. Vikram Sarabhai Space Centre, Thiruvananthapuram provided the electronic design, assembly, and testing. ISRO Satellite Centre (ISAC), Bengaluru provided the mechanical design, quality consultation, and project management. The Inter-University Centre for Astronomy and Astrophysics (IUCAA), Pune did the Coded Mask design, instrument calibration, and Payload Operation Centre. The Space Application Centre (SAC) at Ahmedabad provided the analysis software. The Physical Research Laboratory (PRL) Ahmedabad provided the polarization detection algorithm and ground calibration. A vast number of industries participated in the fabrication and the university sector pitched in by participating in the test and evaluation of the payload. The Indian Space Research Organisation funded, managed, and facilitated the project. This work was supported by the GROWTH project funded by the National Science Foundation under grant No. 1545949. GROWTH is a collaborative project between California Institute of Technology (USA), Pomona College (USA), San Diego State University (USA), Los Alamos National Laboratory (USA), University of Maryland College Park (USA), University of Wisconsin Milwaukee (USA), Tokyo Institute of Technology (Japan), National Central University (Taiwan), Indian Institute of Astrophysics (India), Inter-University Center for Astronomy and Astrophysics (India), Weizmann Institute of Science (Israel), The Oskar Klein Centre at Stockholm University (Sweden), Humboldt University (Germany). The authors acknowledge the support of the Science and Engineering Research Board, Department of Science and Technology, India. These results made use of the Discovery Channel Telescope at Lowell Observatory. Lowell is a private, non-profit institution dedicated to astrophysical research and the public appreciation of astronomy, and operates the DCT in partnership with Boston University, the University of Maryland, the University of Toledo, Northern Arizona University, and Yale University. The Large Monolithic Imager was built by Lowell Observatory using funds provided by the National Science Foundation (AST-1005313). The author(s) also acknowledge the support of the Japan Society for the Promotion of Science. We acknowledge support for the MITSuME Telescope at Akeno by the Inter-University Research Program of the Institute for Cosmic Ray Research, the University of Tokyo. We thank Yoichi Yatsu, Yutaro Tachibana, Yoshihiko Saito, and Kotaro Morita for help with the Akeno observations. The AMI telescope team gratefully acknowledges support from the European Research Council under grant ERC-2012-StG-307215 LODESTONE, the UK Science and Technology Facilities Council (STFC) and the University of Cambridge. A.C. acknowledges support from the National Science Foundation under CAREER grant No. 1455090. V.B. acknowledges support from the INSPIRE program of the Department of Science and Technology, Government of India. J. Mao is supported by the National Natural Science Foundation of China 11673062, 11661161010, the Hundred Talent Program of the Chinese Academy of Sciences, the Major Program of the Chinese Academy of Sciences (KJZD-EW-M06), and the Oversea Talent Program of Yunnan Province. This research has made use of the NASA/ IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. PyRAF is a product of the Space Telescope Science Institute, which is operated by AURA for NASA. Software: Python (van Rossum 1995), Astropy (The Astropy Collaboration et al. 2013), Numpy (van der Walt et al. 2011), Scipy (Jones et al. 2001), DAOPHOT (Stetson 1987), FTOOLS (Blackburn 1995), GEANT4 (Agostinelli et al. 2003), CASA (McMullin et al. 2007), AMI-REDUCE (Davies et al. 2009; Perrott et al. 2013), IRAF (Tody 1986, 1993).

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