TITLE: GCN CIRCULAR NUMBER: 33903 SUBJECT: LIGO/Virgo/KAGRA S230601bf: Identification of a GW compact binary merger candidate DATE: 23/06/01 23:28:00 GMT FROM: S. P. Stevenson at Swinburne University of Technology simon.stevenson@ligo.org
The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report:
We identified the compact binary merger candidate S230601bf during real-time processing of data from LIGO Hanford Observatory (H1) and LIGO Livingston Observatory (L1) at 2023-06-01 22:41:34.101 UTC (GPS time: 1369694512.101). The candidate was found by the CWB [1], MBTA [2], GstLAL [3], oLIB [4], PyCBC Live [5], and SPIIR [6] analysis pipelines.
S230601bf is an event of interest because its false alarm rate, as estimated by the online analysis, is 1.7e-15 Hz, or about one in 1e7 years. The event's properties can be found at this URL:
https://gracedb.ligo.org/superevents/S230601bf
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%. [7] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [7] Both HasNS and HasRemnant consider the support of several neutron star equations of state. The probability that any one of the binary components lie between 3 to 5 solar mass (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 [8], distributed via GCN notice about 31 seconds after the candidate event time. * bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [8], 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 2109 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 3578 +/- 998 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] Aubin et al. CQG 38, 095004 (2021) [3] Tsukada et al. arXiv:2305.06286 (2023) and Ewing et al. arXiv:2305.05625 (2023) [4] Lynch et al. PRD 95, 104046 (2017) [5] Dal Canton et al. ApJ 923, 254 (2021) [6] Chu et al. PRD 105, 024023 (2022) [7] Chatterjee et al. The Astrophysical Journal 896, 54 (2020) [8] Singer & Price PRD 93, 024013 (2016)