{
"subject": "LIGO/Virgo/KAGRA S230920al: Identification of a GW compact binary merger candidate",
"submittedHow": "web",
"bibcode": "2023GCN.34741....1L",
"createdOn": 1695206340228,
"circularId": 34741,
"submitter": "Nikolaos Stergioulas at Aristotle University of Thessaloniki ",
"body": "The LIGO Scientific Collaboration, the Virgo Collaboration, and the\nKAGRA Collaboration report:\n\nWe identified the compact binary merger candidate S230920al during\nreal-time processing of data from LIGO Hanford Observatory (H1) and\nLIGO Livingston Observatory (L1) at 2023-09-20 07:11:24.729 UTC (GPS\ntime: 1379229102.729). The candidate was found by the CWB [1], GstLAL\n[2], MBTA [3], PyCBC Live [4], and SPIIR [5] analysis pipelines.\n\nS230920al is an event of interest because its false alarm rate, as\nestimated by the online analysis, is 3.2e-10 Hz, or about one in 1e2\nyears. The event's properties can be found at this URL:\n\nhttps://gracedb.ligo.org/superevents/S230920al\n\nThe classification of the GW signal, in order of descending\nprobability, is BBH (>99%), Terrestrial (<1%), BNS (<1%), or NSBH\n(<1%).\n\nAssuming the candidate is astrophysical in origin, the probability\nthat the lighter compact object is consistent with a neutron star mass\n(HasNS) is <1%. [6] Using the masses and spins inferred from the\nsignal, the probability of matter outside the final compact object\n(HasRemnant) is <1%. [6] Both HasNS and HasRemnant consider the\nsupport of several neutron star equations of state. The probability\nthat either of the binary components lies between 3 and 5 solar masses\n(HasMassgap) is <1%.\n\nTwo sky maps are available at this time and can be retrieved from the\nGraceDB event page:\n * bayestar.multiorder.fits,0, an initial localization generated by\nBAYESTAR [7], distributed via GCN notice about 29 seconds after the\ncandidate event time.\n * bayestar.multiorder.fits,1, an initial localization generated by\nBAYESTAR [7], distributed via GCN notice about 5 minutes after the\ncandidate event time.\n\nThe preferred sky map at this time is bayestar.multiorder.fits,1. For\nthe bayestar.multiorder.fits,1 sky map, the 90% credible region is\n2125 deg2. Marginalized over the whole sky, the a posteriori\nluminosity distance estimate is 3164 +/- 923 Mpc (a posteriori mean\n+/- standard deviation).\n\nFor further information about analysis methodology and the contents of\nthis alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide\nhttps://emfollow.docs.ligo.org/userguide/.\n\n [1] Klimenko et al. PRD 93, 042004 (2016)\n [2] Tsukada et al. arXiv:2305.06286 (2023) and Ewing et al.\narXiv:2305.05625 (2023)\n [3] Aubin et al. CQG 38, 095004 (2021)\n [4] Dal Canton et al. ApJ 923, 254 (2021)\n [5] Chu et al. PRD 105, 024023 (2022)\n [6] Chatterjee et al. ApJ 896, 54 (2020)\n [7] Singer & Price PRD 93, 024013 (2016)\n"
}