LIGO/Virgo/KAGRA S230922q

The LIGO Scientific Collaboration, the Virgo Collaboration, and the
KAGRA Collaboration report:

We identified the compact binary merger candidate S230922q during
real-time processing of data from LIGO Hanford Observatory (H1) and
LIGO Livingston Observatory (L1) at 2023-09-22 04:06:58.085 UTC (GPS
time: 1379390836.085). The candidate was found by the CWB [1], GstLAL
[2], MBTA [3], and PyCBC Live [4] analysis pipelines.

S230922q is an event of interest because its false alarm rate, as
estimated by the online analysis, is 3.6e-10 Hz, or about one in 87
years. The event's properties can be found at this URL:

https://gracedb.ligo.org/superevents/S230922q

The classification of the GW signal, in order of descending
probability, is BBH (>99%), Terrestrial (<1%), 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%. [5] Using the masses and spins inferred from the
signal, the probability of matter outside the final compact object
(HasRemnant) is <1%. [5] 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,0, an initial localization generated by
BAYESTAR [6], distributed via GCN notice about 24 seconds after the
candidate event time.
 * bayestar.multiorder.fits,1, an initial localization generated by
BAYESTAR [6], 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
3975 deg2. Marginalized over the whole sky, the a posteriori
luminosity distance estimate is 1110 +/- 313 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] Klimenko et al. PRD 93, 042004 (2016)
 [2] Tsukada et al. arXiv:2305.06286
Loading...
 
  (2023) and Ewing et al.
arXiv:2305.05625
Loading...
 
  (2023)
 [3] Aubin et al. CQG 38, 095004 (2021)
 [4] Dal Canton et al. ApJ 923, 254 (2021)
 [5] Chatterjee et al. ApJ 896, 54 (2020)
 [6] Singer & Price PRD 93, 024013 (2016)

The LIGO Scientific Collaboration, the Virgo Collaboration, and the
KAGRA Collaboration report:

We have conducted further analysis of the LIGO Hanford Observatory
(H1) and LIGO Livingston Observatory (L1) data around the time of the
compact binary merger (CBC) candidate S230922q (GCN Circular 34756
Loading...
 
 ). 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/S230922q

For the Bilby.offline0.multiorder.fits,0 sky map, the 90% credible
region is 4658 deg2. Marginalized over the whole sky, the a posteriori
luminosity distance estimate is 6653 +/- 2348 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] Ashton et al. ApJS 241, 27 (2019)