TITLE: GCN CIRCULAR NUMBER: 18889 SUBJECT: LIGO/Virgo G211117: Refined localization from CBC parameter estimation DATE: 16/01/18 15:55:50 GMT FROM: Leo Singer at NASA/GSFC The LIGO Scientific Collaboration and Virgo report: We have completed a Bayesian parameter estimation analysis of the GW candidate G211117 (GCN 18728) under the assumption that the signal arises from a compact binary coalescence (CBC) and using the initial online calibration of the GW strain data. The data is most consistent with a binary black hole merger. One refined sky map is now available and can be retrieved from GraceDB (https://gracedb.ligo.org/events/G211117): * LALInference_skymap.fits.gz, using Bayesian Markov-chain Monte Carlo and nested sampling to perform forward modeling of the full GW signal including spin precession and regression of systematic calibration errors. We expect that additional parameter estimation runs based on the offline re-calibration of the GW data and additional waveform approximants will yield consistent results. We regard this sky map as the most accurate to date for this event. This sky map agrees with the initial BAYESTAR and cWB localizations on favoring two broad, disjoint segments of an annulus. The table below presents a quantitative comparison of the available localizations along the lines of Sec. 4.5 of Essick et al. (2015, http://adsabs.harvard.edu/abs/2015ApJ...800...81E). The first column gives the area in deg2 of the 90% credible region, and the second column gives the area in deg2 of the overlap with the LALInference 90% credible region. Area Overlap Algorithm (filename) ------------------------------------------------------------- 1340 1090 BAYESTAR (bayestar.fits.gz) 2230 1180 cWB (skyprobcc_cWB.fits) 1240 ---- LALInference (LALInference_skymap.fits.gz)