A1 Refereed original research article in a scientific journal
Observations of the GRB Afterglow ATLAS17aeu and Its Possible Association with GW170104
Authors: Stalder B, Tonry J, Smartt SJ, Coughlin M, Chambers KC, Stubbs CW, Chen TW, Kankare E, Smith KW, Denneau L, Sherstyuk A, Heinze A, Weiland H, Rest A, Young DR, Huber ME, Flewelling H, Lowe T, Magnier EA, Schultz ASB, Waters C, Wainscoat R, Willman M, Wright DE, Chu J, Sanders D, Inserra C, Maguire K, Kotak R, Kotak R
Publisher: IOP PUBLISHING LTD
Publication year: 2017
Journal: Astrophysical Journal
Journal name in source: ASTROPHYSICAL JOURNAL
Journal acronym: ASTROPHYS J
Article number: ARTN 149
Volume: 850
Issue: 2
Number of pages: 13
ISSN: 0004-637X
DOI: https://doi.org/10.3847/1538-4357/aa95c1
Self-archived copy’s web address: https://research.utu.fi/converis/portal/Publication/39037824
We report the discovery and multiwavelength data analysis of the peculiar optical transient, ATLAS17aeu. This transient was identified in the sky map of the LIGO gravitational wave event GW 170104 by our ATLAS and Pan-STARRS coverage. ATLAS17aeu was discovered 23.1 hr after GW 170104 and rapidly faded over the next three nights, with a spectrum revealing a blue featureless continuum. The transient was also detected as a fading X-ray source by Swift and in the radio at 6 and 15 GHz. The gamma-ray burst GRB 170105A was detected by three satellites 19.04 hr after GW 170104 and 4.10 hr before our first optical detection. We analyze the multiwavelength fluxes in the context of the known GRB population and discuss the observed sky rates of GRBs and their afterglows. We find it statistically likely that ATLAS17aeu is an afterglow associated with GRB 170105A, with a chance coincidence ruled out at the 99% confidence or 2.6 sigma. A long, soft GRB within a redshift range of 1 less than or similar to z less than or similar to 2.9 would be consistent with all the observed multiwavelength data. The Poisson probability of a chance occurrence of GW 170104 and ATLAS17aeu is p = 0.04. This is the probability of a chance coincidence in 2D sky location and in time. These observations indicate that ATLAS17aeu is plausibly a normal GRB afterglow at significantly higher redshift than the distance constraint for GW 170104 and therefore a chance coincidence. However, if a redshift of the faint host were to place it within the GW 170104 distance range, then physical association with GW 170104 should be considered.
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