LIGO/Virgo/KAGRA S240915bd
GCN Circular 37514
Subject
LIGO/Virgo/KAGRA S240915bd: Identification of a GW compact binary merger candidate
Date
2024-09-15T11:18:49Z (8 months ago)
From
Ulyana Dupletsa <ulyana.dupletsa@gssi.it>
Via
Web form
The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report:
We identified the compact binary merger candidate S240915bd during real-time processing of data from LIGO Hanford Observatory (H1) and Virgo Observatory (V1) at 2024-09-15 10:51:51.059 UTC (GPS time: 1410432729.059). The candidate was found by the GstLAL [1] analysis pipeline.
S240915bd is an event of interest because its false alarm rate, as estimated by the online analysis, is 3.3e-14 Hz, or about one in 1e6 years. The event's properties can be found at this URL:
https://gracedb.ligo.org/superevents/S240915bd
The classification of the GW signal, in order of descending probability, is BBH (>99%), NSBH (<1%), Terrestrial (<1%), or BNS (<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 10%.
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 [3], distributed via GCN notice about 27 seconds after the candidate event time.
* bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [3], 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 5115 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 659 +/- 176 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] Tsukada et al. PRD 108, 043004 (2023) doi:10.1103/PhysRevD.108.043004 and Ewing et al. (2023) arXiv:2305.05625
[2] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe
[3] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013
GCN Circular 37516
Subject
LIGO/Virgo/KAGRA S240915bd: Updated Sky localization
Date
2024-09-15T14:22:10Z (8 months ago)
From
Nelson Christensen at Obs.de la Cote dAzur,Nice <nelson.christensen@oca.eu>
Via
Web form
The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report:
We have conducted further analysis of the LIGO Hanford Observatory (H1) and Virgo Observatory (V1) data around the time of the compact binary merger (CBC) candidate S240915bd (GCN Circular 37514). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.multiorder.fits,0, distributed via GCN Notice, is available for retrieval from the GraceDB event page:
https://gracedb.ligo.org/superevents/S240915bd
For the Bilby.multiorder.fits,0 sky map, the 90% credible region is 4244 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 612 +/- 139 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] Ashton et al. ApJS 241, 27 (2019) doi:10.3847/1538-4365/ab06fc and Morisaki et al. PRD 108, 123040 (2023) doi:10.1103/PhysRevD.108.123040