TITLE: GCN CIRCULAR NUMBER: 37646 SUBJECT: LIGO/Virgo/KAGRA S240930du: Identification of a GW compact binary merger candidate DATE: 24/10/01 01:42:32 GMT FROM: takada@icrr.u-tokyo.ac.jp The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We identified the compact binary merger candidate S240930du during real-time processing of data from LIGO Hanford Observatory (H1) and LIGO Livingston Observatory (L1) at 2024-09-30 23:46:14.945 UTC (GPS time: 1411775192.945). The candidate was found by the cWB BBH [1] analysis pipeline. S240930du is an event of interest because its false alarm rate, as estimated by the online analysis, is 1.3e-08 Hz, or about one in 2 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S240930du The classification of the GW signal, in order of descending probability, is BBH (67%), Terrestrial (33%), 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%. [2] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [2] Both HasNS and HasRemnant consider the support of several neutron star equations of state for maximum neutron star mass. 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: * cwb.multiorder.fits,0, an initial localization generated by cWB [3], distributed via GCN notice about a minute after the candidate event time. * cwb.multiorder.fits,1, an initial localization generated by cWB [3], distributed via GCN notice about 5 minutes after the candidate event time. The preferred sky map at this time is cwb.multiorder.fits,1. For the cwb.multiorder.fits,1 sky map, the 90% credible region is 1280 deg2. 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/. [1] T. Mishra et al. PRD 105, 083018 (2022) doi:10.1103/PhysRevD.105.083018 [2] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe [3] Klimenko et al. PRD 93, 042004 (2016) doi:10.1103/PhysRevD.93.042004 View this GCN Circular online at https://gcn.nasa.gov/circulars/37646. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...