TITLE:   GCN CIRCULAR
NUMBER:  27419
SUBJECT: LIGO/Virgo S200316bj: Updated Sky Localization and EM Bright Classification
DATE:    20/03/21 17:07:55 GMT
FROM:    Deep Chatterjee at University of Wisconsin, Milwaukee  <deep@uwm.edu>

The LIGO Scientific Collaboration and the Virgo Collaboration report:

We have conducted further analysis of the LIGO Hanford Observatory
(H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1)
data around the time of the compact binary merger (CBC) candidate
S200316bj (GCN Circular 27388). Parameter estimation has been
performed using LALInference [1] and a new sky map,
LALInference.fits.gz,0, distributed via GCN Notice, is available for
retrieval from the GraceDB event page:

https://gracedb.ligo.org/superevents/S200316bj

The preferred sky map at this time is LALInference.fits.gz,0. For the
LALInference.fits.gz,0 sky map, the 90% credible region is 508 deg2.
Marginalized over the whole sky, the a posteriori luminosity distance
estimate is 1178 +/- 283 Mpc (a posteriori mean +/- standard
deviation).

Based on posterior support from parameter estimation [1], under the
assumption that the candidate S200316bj is astrophysical in origin,
the probability that the lighter compact object has a mass < 3 solar
masses (HasNS) is <1%. Using the masses and spins inferred from the
signal, the probability of matter outside the final compact object
(HasRemnant) is <1%.

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)