Follow Up of GW170817 and Its Electromagnetic Counterpart by Australian-Led Observing Programmes
The discovery of the first electromagnetic counterpart to a gravitational wave signal has generated follow-up observations by over 50 facilities world-wide, ushering in the new era of multi-messenger astronomy. In this paper, we present follow-up observations of the gravitational wave event GW170817 and its electromagnetic counterpart SSS17a/DLT17ck (IAU label AT2017gfo) by 14 Australian telescopes and partner observatories as part of Australian-based and Australian-led research programs. We report early- to late-time multi-wavelength observations, including optical imaging and spectroscopy, mid-infrared imaging, radio imaging, and searches for fast radio bursts. Our optical spectra reveal that the transient source emission cooled from approximately 6 400 K to 2 100 K over a 7-d period and produced no significant optical emission lines. The spectral profiles, cooling rate, and photometric light curves are consistent with the expected outburst and subsequent processes of a binary neutron star merger. Star formation in the host galaxy probably ceased at least a Gyr ago, although there is evidence for a galaxy merger. Binary pulsars with short (100 Myr) decay times are therefore unlikely progenitors, but pulsars like PSR B1534+12 with its 2.7 Gyr coalescence time could produce such a merger. The displacement (~2.2 kpc) of the binary star system from the centre of the main galaxy is not unusual for stars in the host galaxy or stars originating in the merging galaxy, and therefore any constraints on the kick velocity imparted to the progenitor are poor.
© 2017 Astronomical Society of Australia. Published online: 20 December 2017. We thank Prof. Brian Metzger who provided the gri light curves for the M15 model. Part of this research was funded by the Australian Research Council Centre of Excellence for Gravitational Wave Discovery (OzGrav), CE170100004 and the Australian Research Council Centre of Excellence for All-sky Astrophysics (CAASTRO), CE110001020. Parts of this research were conducted by the Australian Research Council Centre of Excellence for All-sky Astrophysics in 3 Dimensions (ASTRO-3D), CE170100013. Research support to IA is provided by the Australian Astronomical Observatory (AAO). JC acknowledges the Australian Research Council Future Fellowship grant FT130101219. The Etelman Observatory team acknowledges support through NASA grants NNX13AD28A and NNX15AP95A. TM acknowledges the support of the Australian Research Council through grant FT150100099. SO acknowledges the Australian Research Council grant Laureate Fellowship FL15010014. DLK and ISB are additionally supported by NSF grant AST-141242.1 PAB and the DFN team acknowledge the Australian Research Council for support under their Australian Laureate Fellowship scheme. C.M. is supported by NSF grant AST-1313484. The Australia Telescope Compact Array is part of the Australia Telescope National Facility which is funded by the Australian Government for operation as a National Facility managed by CSIRO. This scientific work makes use of the Murchison Radio-astronomy Observatory, operated by CSIRO. We acknowledge the Wajarri Yamatji people as the traditional owners of the Observatory site. Support for the operation of the MWA is provided by the Australian Government (NCRIS), under a contract to Curtin University administered by Astronomy Australia Limited. We acknowledge the Pawsey Supercomputing Centre which is supported by the Western Australian and Australian Governments. The Australian SKA Pathfinder is part of the Australia Telescope National Facility which is managed by CSIRO. Operation of ASKAP is funded by the Australian Government with support from the National Collaborative Research Infrastructure Strategy. ASKAP uses the resources of the Pawsey Supercomputing Centre. Establishment of ASKAP, the Murchison Radio-astronomy Observatory and the Pawsey Supercomputing Centre are initiatives of the Australian Government, with support from the Government of Western Australia and the Science and Industry Endowment Fund. We acknowledge the Wajarri Yamatji people as the traditional owners of the Observatory site. This work was supported by resources provided by the Pawsey Supercomputing Centre with funding from the Australian Government and the Government of Western Australia. The Long Baseline Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. The Zadko Telescope is supported by the University of Western Australia Department of Physics, in the Faculty of Engineering and Mathematical Sciences. We also thank the superb technical support from J. Moore and A. Burrel that has enabled the facility to participate in this project. SkyMapper is owned and operated by The Australian National University's Research School of Astronomy and Astrophysics. The national facility capability for SkyMapper has been funded through ARC LIEF grant LE130100104 from the Australian Research Council, awarded to the University of Sydney, the Australian National University, Swinburne University of Technology, the University of Queensland, the University of Western Australia, the University of Melbourne, Curtin University of Technology, Monash University and the Australian Astronomical Observatory. The AST3 project is supported by the National Basic Research Program (973 Program) of China (Grant No. 2013CB834900), and the Chinese Polar Environment Comprehensive Investigation & Assessment Program (Grand No. CHINARE2016-02-03-05). The construction of the AST3 telescopes has received fundings from Tsinghua University, Nanjing University, Beijing Normal University, University of New South Wales, Texas A&M University, the Australian Antarctic Division, and the National Collaborative Research Infrastructure Strategy (NCRIS) of Australia. It has also received fundings from Chinese Academy of Sciences through the Center for Astronomical Mega-Science and National Astronomical Observatory of China (NAOC). Based in part on data acquired through the Australian Astronomical Observatory. We acknowledge the traditional owners of the land on which the AAT stands, the Gamilaraay people, and pay our respects to elders past and present. Some of the observations reported in this paper were obtained with the Southern African Large Telescope (SALT) under the Director's Discretionary Time programme 2017-1-DDT-009. The SALT/SAAO team are supported by the National Research Foundation (NRF) of South Africa. Research partially based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme 60.A-9392.
Submitted - 1710.05846.pdf