LIGO/Virgo/KAGRA S231118ab
GCN Circular 35094
Subject
LIGO/Virgo/KAGRA S231118ab: Identification of a GW compact binary merger candidate
Date
2023-11-18T08:05:49Z (2 years ago)
From
valeria.sequino@na.infn.it
Via
Web form
The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report:
We identified the compact binary merger candidate S231118ab during real-time processing of data from LIGO Hanford Observatory (H1) and LIGO Livingston Observatory (L1) at 2023-11-18 07:14:02.239 UTC (GPS time: 1384326860.239). The candidate was found by the CWB [1], GstLAL [2], MBTA [3], PyCBC Live [4], and SPIIR [5] analysis pipelines.
S231118ab is an event of interest because its false alarm rate, as estimated by the online analysis, is 1.9e-08 Hz, or about one in 1 year, 8 months. The event's properties can be found at this URL:
https://gracedb.ligo.org/superevents/S231118ab
The classification of the GW signal, in order of descending probability, is BBH (99%), Terrestrial (1%), BNS (<1%), or NSBH (<1%).
Assuming the candidate is astrophysical in origin, the probability that the lighter compact object is consistent with a neutron star mass (HasNS) is <1%. [6] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [6] 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%.
Two sky maps are available at this time and can be retrieved from the GraceDB event page:
* bayestar.multiorder.fits,0, an initial localization generated by BAYESTAR [7], distributed via GCN notice about 29 seconds after the candidate event time.
* bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [7], distributed via GCN notice about 5 minutes after the candidate event time.
The preferred sky map at this time is bayestar.multiorder.fits,1. For the bayestar.multiorder.fits,1 sky map, the 90% credible region is 3197 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 4531 +/- 1498 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] Klimenko et al. PRD 93, 042004 (2016)
[2] Tsukada et al. PRD 108, 043004 (2023) and Ewing et al. arXiv:2305.05625 (2023)
[3] Aubin et al. CQG 38, 095004 (2021)
[4] Dal Canton et al. ApJ 923, 254 (2021)
[5] Chu et al. PRD 105, 024023 (2022)
[6] Chatterjee et al. ApJ 896, 54 (2020)
[7] Singer & Price PRD 93, 024013 (2016)
GCN Circular 35145
Subject
LIGO/Virgo/KAGRA S231118ab: Updated Sky localization and Source Classification
Date
2023-11-20T21:06:08Z (2 years ago)
From
jgolomb@caltech.edu
Via
Web form
The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report:
We have conducted further offline analysis of the LIGO Hanford Observatory (H1) and LIGO Livingston Observatory (L1) data around the time of the compact binary merger (CBC) candidate S231118ab (GCN Circular 35094). 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/S231118ab
After parameter estimation by RapidPE-RIFT [2], the updated classification of the GW signal, in order of descending probability, is BBH (99%), Terrestrial (1%), NSBH (<1%), or BNS (0%).
For the Bilby.offline0.multiorder.fits,0 sky map, the 90% credible region is 2898 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 4353 +/- 1588 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] Rose et al. arXiv:2201.05263 (2022) and Pankow et al. PRD 92, 023002 (2015)