TITLE: GCN CIRCULAR NUMBER: 34195 SUBJECT: LIGO/Virgo/KAGRA S230708z: Identification of a GW compact binary merger candidate DATE: 23/07/10 15:58:45 GMT FROM: adrian.helmling-cornell@ligo.org The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We identified the compact binary merger candidate S230708z during real-time processing of data from LIGO Hanford Observatory (H1) and LIGO Livingston Observatory (L1) at 2023-07-08 07:18:59.444 UTC (GPS time: 1372835957.444). The candidate was found by the CWB [1], MBTA [2], and GstLAL [3] analysis pipelines. S230708z is an event of interest because its false alarm rate, as estimated by the online analysis, is 7e-08 Hz, or about one in 5 months. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S230708z The classification of the GW signal, in order of descending probability, is BBH (95%), Terrestrial (5%), NSBH (<1%), or BNS (<1%). There was a high rate of noise transients (glitches) in the LIGO Livingston detector which may affect the parameters or the significance of the candidate. Assuming the candidate is astrophysical in origin, the probability that the lighter compact object is consistent with a neutron star mass (HasNS) is <1%. [4] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [4] 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 [5], distributed via GCN notice about 24 seconds after the candidate event time. * bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [5], 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 3111 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 5796 +/- 1854 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] Chatterjee et al. ApJ 896, 54 (2020) [5] Singer & Price PRD 93, 024013 (2016) --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...