TITLE: GCN CIRCULAR NUMBER: 38975 SUBJECT: LIGO/Virgo/KAGRA S250118dp: Identification of a GW compact binary merger candidate DATE: 25/01/18 17:37:47 GMT FROM: julio.martins@ligo.org
The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report:
We identified the compact binary merger candidate S250118dp during real-time processing of data from LIGO Hanford Observatory (H1) and LIGO Livingston Observatory (L1) at 2025-01-18 17:05:23.221 UTC (GPS time: 1421255141.221). The candidate was found by the CWB [1], CWB-BBH [2], GstLAL [3], MBTA [4], PyCBC Live [5], and SPIIR [6] analysis pipelines.
S250118dp is an event of interest because its false alarm rate, as estimated by the online analysis, is 5.6e-25 Hz, or about one in 1e17 years. The event's properties can be found at this URL:
https://gracedb.ligo.org/superevents/S250118dp
The classification of the GW signal, in order of descending probability, is BBH (>99%), NSBH (<1%), BNS (<1%), or Terrestrial (<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 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,1, an initial localization generated by BAYESTAR [8], distributed via GCN notice about 30 seconds after the candidate event time. * bayestar.multiorder.fits,2, 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,2. For the bayestar.multiorder.fits,2 sky map, the 90% credible region is 1136 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 2125 +/- 569 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/.
[1] Klimenko et al. PRD 93, 042004 (2016) doi:10.1103/PhysRevD.93.042004 [2] T. Mishra et al. PRD 105, 083018 (2022) doi:10.1103/PhysRevD.105.083018 [3] Tsukada et al. PRD 108, 043004 (2023) doi:10.1103/PhysRevD.108.043004 and Ewing et al. (2023) arXiv:2305.05625 [4] Aubin et al. CQG 38, 095004 (2021) doi:10.1088/1361-6382/abe913 [5] Dal Canton et al. ApJ 923, 254 (2021) doi:10.3847/1538-4357/ac2f9a [6] Chu et al. PRD 105, 024023 (2022) doi:10.1103/PhysRevD.105.024023 [7] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe [8] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013
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