TITLE: GCN CIRCULAR NUMBER: 38149 SUBJECT: LIGO/Virgo/KAGRA S241109bn: Updated Sky localization and EM Bright Classification DATE: 24/11/09 23:38:36 GMT FROM: Aditya Vijaykumar aditya.vijaykumar@ligo.org
The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report:
We have conducted further analysis of the LIGO Hanford Observatory (H1) and Virgo Observatory (V1) data around the time of the compact binary merger (CBC) candidate S241109bn (GCN Circular 38142). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.offline0.multiorder.fits,0, distributed via GCN Notice, is available for retrieval from the GraceDB event page:
https://gracedb.ligo.org/superevents/S241109bn
Based on posterior support from parameter estimation [1], under the assumption that the candidate S241109bn is astrophysical in origin, the probability that at least one of the compact objects is consistent with a neutron star (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 for maximum neutron star mass. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is 43%.
Preliminary information from parameter estimation seems to indicate a much smaller NSBH probability than initially reported (GCN Circular 38142), and almost certainly a BBH origin.
For the Bilby.offline0.multiorder.fits,0 sky map, the 90% credible region is 10138 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 603 +/- 159 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/.
[1] Ashton et al. ApJS 241, 27 (2019) doi:10.3847/1538-4365/ab06fc and Morisaki et al. PRD 108, 123040 (2023) doi:10.1103/PhysRevD.108.123040 [2] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbez
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