TITLE: GCN CIRCULAR NUMBER: 20385 SUBJECT: LIGO/Virgo G268556: Updated sky map from gravitational-wave data DATE: 17/01/06 21:44:29 GMT FROM: Giuseppe Greco at U degli Studi di Urbino The LIGO Scientific Collaboration and Virgo report: We have re-analyzed LIGO data around the time of the compact binary coalescence (CBC) event candidate G268556 (GCN 20364) taking into account our current understanding of calibration uncertainties. Although a full recalibration remains to be done, we expect that this event will be confirmed with a false alarm rate (FAR) of less than 1 per 100 years. Parameter estimation has been performed using LALInference (Veitch et al., PRD 91, 042003) and a new sky map, LALInference_skymap.fits.gz, is available for retrieval from the GraceDB event page: https://gracedb.ligo.org/events/G268556 This is the preferred sky map at this time. This map has two arcs in nearly the same positions as the original BAYESTAR sky map but the probability is divided more equally between the northern and southern arcs. The 50% and 90% credible regions span about 500 deg2 and 2000 deg2, respectively, which are somewhat larger than the initial BAYESTAR sky map due to marginalizing over calibration uncertainties. We will recalculate the sky map once the full recalibration is complete and will share it at that time, but that is likely at least a few weeks away.