GCN Circular 37557

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 S240917cb (GCN Circular 37534
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). 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/S240917cb

Based on posterior support from parameter estimation [1], under the assumption that the candidate S240917cb 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 <1%.

For the Bilby.offline0.multiorder.fits,0 sky map, the 90% credible region is 8644 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 6657 +/- 3466 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
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 and Morisaki et al. PRD 108, 123040 (2023) doi:10.1103/PhysRevD.108.123040
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 [2] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe
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