{
"subject": "LIGO/Virgo/KAGRA S230708t: Identification of a GW compact binary merger candidate",
"bibcode": "2023GCN.34194....1L",
"createdOn": 1689003078388,
"circularId": 34194,
"submitter": "adrian.helmling-cornell@ligo.org",
"body": "The LIGO Scientific Collaboration, the Virgo Collaboration, and the\nKAGRA Collaboration report:\n\nWe identified the compact binary merger candidate S230708t during\nreal-time processing of data from LIGO Hanford Observatory (H1) and\nLIGO Livingston Observatory (L1) at 2023-07-08 05:37:05.120 UTC (GPS\ntime: 1372829843.120). The candidate was found by the MBTA [1] and\nGstLAL [2] analysis pipelines.\n\nS230708t is an event of interest because its false alarm rate, as\nestimated by the online analysis, is 4.3e-08 Hz, or about one in 8\nmonths. The event's properties can be found at this URL:\n\nhttps://gracedb.ligo.org/superevents/S230708t\n\nThe classification of the GW signal, in order of descending\nprobability, is BBH (97%), Terrestrial (3%), NSBH (<1%), or BNS (<1%).\n\nThere was a high rate of noise transients (glitches) in the LIGO Hanford \ndetector which may affect the parameters or the significance of \nthe candidate.\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%. [3] Using the masses and spins inferred from the\nsignal, the probability of matter outside the final compact object\n(HasRemnant) is <1%. [3] 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\nThree sky maps are available at this time and can be retrieved from\nthe GraceDB event page:\n * bayestar.multiorder.fits,0, an initial localization generated by\nBAYESTAR [4], distributed via GCN notice about 27 seconds after the\ncandidate event time.\n * bayestar.multiorder.fits,1, an initial localization generated by\nBAYESTAR [4], distributed via GCN notice about 36 seconds after the\ncandidate event time.\n * bayestar.multiorder.fits,2, an initial localization generated by\nBAYESTAR [4], distributed via GCN notice about 5 minutes after the\ncandidate event time.\n\nThe preferred sky map at this time is bayestar.multiorder.fits,2. For\nthe bayestar.multiorder.fits,2 sky map, the 90% credible region is\n2292 deg2. Marginalized over the whole sky, the a posteriori\nluminosity distance estimate is 3372 +/- 1101 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] Aubin et al. CQG 38, 095004 (2021)\n [2] Tsukada et al. arXiv:2305.06286 (2023) and Ewing et al.\narXiv:2305.05625 (2023)\n [3] Chatterjee et al. ApJ 896, 54 (2020)\n [4] Singer & Price PRD 93, 024013 (2016)"
}