TITLE:   GCN CIRCULAR
NUMBER:  35034
SUBJECT: LIGO/Virgo/KAGRA S231113bw: Updated Sky localization, EM Bright Classification, and Source Classification
DATE:    23/11/15 01:32:36 GMT
FROM:    jgolomb@caltech.edu

The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report:

We have conducted further analysis of the LIGO Hanford Observatory (H1) and LIGO Livingston Observatory (L1) data around the time of the compact binary merger (CBC) candidate S231113bw (GCN Circular 35016). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.multiorder.fits, distributed via GCN Notice, is available for retrieval from the GraceDB event page:

https://gracedb.ligo.org/superevents/S231113bw

Based on posterior support from parameter estimation [1], under the assumption that the candidate S231113bw is astrophysical in origin, the probability that the lighter compact object is consistent with a neutron star mass (HasNS) is <1%. [2] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [2] Both HasNS and HasRemnant consider the support of several neutron star equations of state. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassgap) is 2%.

After parameter estimation by RapidPE-RIFT [3], the updated classification of the GW signal, in order of descending probability, is BBH (96%), Terrestrial (4%), NSBH (<1%), or BNS (<1%).

For the Bilby.multiorder.fits sky map, the 90% credible region is 1713 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 1186 +/- 376 Mpc (a posteriori mean +/- standard deviation).

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

 [1] Ashton et al. ApJS 241, 27 (2019) and Morisaki et al. arXiv:2307.13380 (2023)
 [2] Chatterjee et al. ApJ 896, 54 (2020)
 [3] Rose et al. arXiv:2201.05263 (2022) and Pankow et al. PRD 92, 023002 (2015)