LIGO/Virgo/KAGRA S240930du
GCN Circular 37646
Subject
LIGO/Virgo/KAGRA S240930du: Identification of a GW compact binary merger candidate
Date
2024-10-01T01:42:32Z (8 months ago)
From
takada@icrr.u-tokyo.ac.jp
Via
Web form
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
GCN Circular 37661
Subject
LIGO/Virgo/KAGRA S240930du: Updated Sky localization
Date
2024-10-01T22:27:24Z (8 months ago)
From
Sylvia Biscoveanu at Northwestern CIERA <sylvia.biscoveanu@ligo.org>
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), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) data around the time of the compact binary merger (CBC) candidate S240930du (GCN Circular 37646). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.offline0.multiorder.fits,0, distributed via GCN Notice, is available for retrieval from the GraceDB event page:
https://gracedb.ligo.org/superevents/S240930du
For the Bilby.offline0.multiorder.fits,0 sky map, the 90% credible region is well fit by an ellipse with an area of 955 deg2 described by the following DS9 region (right ascension, declination, semi-major axis, semi-minor axis, position angle of the semi-minor axis):
icrs; ellipse(07h25m, -17d26m, 35.87d, 8.65d, 41.28d)
Marginalized over the whole sky, the a posteriori luminosity distance estimate is 3874 +/- 1404 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