TITLE: GCN CIRCULAR NUMBER: 21751 SUBJECT: LIGO/Virgo G298936: Updated localization from parameter estimation on LIGO and Virgo data DATE: 17/08/29 15:55:12 GMT FROM: Leo Singer at NASA/GSFC The LIGO Scientific Collaboration and the Virgo Collaboration report: We have re-analyzed data from LIGO Hanford Observatory (H), LIGO Livingston Observatory (L), and Virgo (V) around the time of the binary black hole merger candidate G298936 (GCNs 21656 and 21661) taking into account our current understanding of calibration uncertainties. Parameter estimation has been performed using LALInference (Veitch et al., PRD 91, 042003) and a new sky map, LALInference_r1.fits.gz, can be retrieved from the GraceDB event page: https://gracedb.ligo.org/events/G298936 This is the preferred sky map at this time. The new localization is consistent with but slightly smaller than the BAYESTAR localization using HLV data (GCN 21661, bayestar-HLV.fits.gz). The 50% area has decreased from 277 to 207 deg2 and the 90% area has decreased from 1219 to 952 deg2. The all-sky, marginalized luminosity distance estimate is 1738 +/- 477 Mpc (a posteriori mean +/- standard deviation), largely consistent with the original estimate.