TITLE:   GCN CIRCULAR
NUMBER:  25138
SUBJECT: LIGO/Virgo S190720a: Updated localization from LIGO and Virgo data
DATE:    19/07/22 18:40:13 GMT
FROM:    John Veitch at U of Glasgow  <john.veitch@ligo.org>

The LIGO Scientific Collaboration and the Virgo Collaboration report:


We have re-analyzed LIGO and Virgo data around the time of the compact
binary coalescence (CBC) candidate S190720a (GCN 25115). Parameter
estimation has been performed using LALInference [1] and a new sky
map, LALInference.offline.fits.gz, is available for retrieval from the
GraceDB event page:


https://gracedb.ligo.org/superevents/S190720a/


This is currently the preferred skymap. For the LALInference.offline.fits.gz 
sky map, the 90% credible region is 443 deg2.
Marginalized over the whole sky, the a posteriori luminosity
distance estimate is 869 +/- 283 Mpc (a posteriori mean +/- standard
deviation). This is the preferred sky map at this time. The LALInference 
skymap is generated using data from three detectors, while the sky map
shared in GCN 25115, was generated from data obtained from two detectors.
This partly contributed to the better localization.


For further information about analysis methodology and the contents
of this alert, refer to the LIGO/Virgo Public Alerts User Guide
<https://emfollow.docs.ligo.org/userguide/>.



[1] Veitch et al. PRD 91, 042003 (2015)