GCN Circular 33889
Subject
LIGO/Virgo/KAGRA S230529ay: Identification of a GW compact binary merger candidate
Date
2023-05-29T18:36:00Z (a year ago)
From
J. L. Wright at Australian National University <jennifer.wright@anu.edu.au>
The LIGO Scientific Collaboration, the Virgo Collaboration, and the
KAGRA Collaboration report:
We identified the compact binary merger candidate S230529ay during
real-time processing of data from LIGO Livingston Observatory (L1) at
2023-05-29 18:15:00.746 UTC (GPS time: 1369419318.746). The candidate
was found by the GstLAL [1] and PyCBC Live [2] analysis pipelines.
S230529ay is an event of interest because its false alarm rate, as
estimated by the online analysis, is 2e-10 Hz, or about one in 1e2
years. The event's properties can be found at this URL:
https://gracedb.ligo.org/superevents/S230529ay
The classification of the GW signal, in order of descending
probability is NSBH (62%), BNS (31%), Terrestrial (7%), or BBH (<1%).
Assuming the candidate is astrophysical in origin, the probability
that the lighter compact object is consistent with a neutron star mass
(HasNS) is >99%. [3] Using the masses and spins inferred from the
signal, the probability of matter outside the final compact object
(HasRemnant) is 12%. [3] Both HasNS and HasRemnant consider the
support of several neutron star equations of state. The probability
that any one of the binary components lie between 3 to 5 solar mass
(HasMassgap) is 98%.
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 [4], distributed via GCN notice about 25 seconds after the
candidate event time.
* bayestar.multiorder.fits,1, an initial localization generated by
BAYESTAR [4], 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
well fit by an ellipse with an area of 31171 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(00h00m, +00d00m, 163.70d, 97.20d, 147.56d)
Marginalized over the whole sky, the a posteriori luminosity distance
estimate is 217 +/- 71 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] Tsukada et al. arXiv:2305.06286 (2023) and Ewing et al. arXiv:2305.05625 (2023)
[2] Dal Canton et al. ApJ 923, 254 (2021)
[3] Chatterjee et al. The Astrophysical Journal 896, 1 (2020)
[4] Singer & Price PRD 93, 024013 (2016)