GCN Circular 20833
The LIGO Scientific Collaboration and Virgo report: We have completed an initial Bayesian parameter estimation analysis of the LIGO data around the time of the compact binary coalescence (CBC) event candidate G275697 (GCN 20763) using LALInference (Veitch et al., PRD 91, 042003). This analysis used the IMRPhenomPv2 waveform approximant, which includes the inspiral, merger, and ringdown phases of the signal and accounts for the effects of spin precession. We accounted for systematic errors due to uncertainty in the calibration of the detectors' responses of up to 10% in amplitude and 10 degrees in phase. This parameter estimation analysis does not influence our estimation of the significance of this event. It remains a marginal candidate with a false alarm rate of about one in two months as reported in our original Circular. If the signal is astrophysical, then the mass estimates are consistent with a NSNS or NSBH binary. An updated localization, LALInference.fits.gz, is available for retrieval from the GraceDB event page: https://gracedb.ligo.org/events/G275697 This is the preferred sky map at this time. The localization is similar to the rapid BAYESTAR sky map, but it is coarser due to the inclusion of systematic errors due to calibration. The 50% credible region spans 1020 deg2 and the 90% credible region spans 3890 deg2. The luminosity distance is found to be 193 +/- 61 Mpc (mean +/- std. dev.). Further updates on our analysis of this event will be sent as they become available.