{
"subject": "LIGO/Virgo G275404: Updated localization from LIGO data",
"bibcode": "2017GCN.20840....1L",
"createdOn": 1489012250000,
"circularId": 20840,
"submitter": "Alex Urban at Caltech ",
"email": "aurban@ligo.caltech.edu",
"body": "The LIGO Scientific Collaboration and Virgo report:\n\nWe have completed an initial Bayesian parameter estimation analysis of\nthe LIGO data around the time of the compact binary coalescence (CBC)\nevent candidate G275404 (GCN 20738) using LALInference (Veitch et al.,\nPRD 91, 042003). This analysis used the IMRPhenomPv2 waveform\napproximation, which includes the inspiral, merger, and ringdown\nphases of the signal and accounts for the effects of spin precession.\nWe accounted for systematic errors due to uncertainty in the\ncalibration of the detectors' responses of up to 10% in amplitude and\n10 degrees in phase. This follow-up analysis also used different, more\nconservative assumptions on the detector noise properties.\n\nThe updated localization, LALInference.fits.gz, is available for\nretrieval from the GraceDB event page:\n\nhttps://gracedb.ligo.org/events/G275404 \n\nThe localization has arcs similar to the rapid BAYESTAR sky map, but\nbroader, and the conservative assumptions mentioned above result in\nthis case in a much larger area in the sky consistent with the\nobserved data. The 50% credible region spans 2000 deg2 and the 90%\ncredible region spans 17000 deg2 due to a diffuse component in the\nprobability distribution.\n\nThis parameter estimation analysis does not influence our estimation\nof the significance of this event. It remains a marginal candidate\nwith a false alarm rate of about one in two months as reported in our\noriginal Circular. If the signal is astrophysical, then the mass\nestimates are consistent with a NSNS or NSBH binary."
}