LIGO/Virgo/KAGRA S230807f

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

We identified the compact binary merger candidate S230807f during
real-time processing of data from LIGO Hanford Observatory (H1) and
LIGO Livingston Observatory (L1) at 2023-08-07 20:50:45.416 UTC (GPS
time: 1375476663.416). The candidate was found by the CWB [1], GstLAL
[2], MBTA [3], PyCBC Live [4], and SPIIR [5] analysis pipelines.

S230807f is an event of interest because its false alarm rate, as
estimated by the online analysis, is 7.1e-08 Hz, or about one in 5
months. The event's properties can be found at this URL:

https://gracedb.ligo.org/superevents/S230807f

The classification of the GW signal, in order of descending
probability, is BBH (86%), Terrestrial (14%), NSBH (<1%), or BNS
(<1%). 

There was a high rate of noise transients (glitches) in both the LIGO 
Livingston and Hanford detectors which may affect the parameters or the significance 
of the candidate.

Assuming the candidate is astrophysical in origin, the probability
that the lighter compact object is consistent with a neutron star mass
(HasNS) is <1%. [6] Using the masses and spins inferred from the
signal, the probability of matter outside the final compact object
(HasRemnant) is <1%. [6] 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 4%.

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 [7], distributed via GCN notice about 35 seconds after the
candidate event time.
 * bayestar.multiorder.fits,2, an initial localization generated by
BAYESTAR [7], 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
6088 deg2. Marginalized over the whole sky, the a posteriori
luminosity distance estimate is 6818 +/- 2379 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
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  (2023) and Ewing et al.
arXiv:2305.05625
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  (2023)
 [3] Aubin et al. CQG 38, 095004 (2021)
 [4] Dal Canton et al. ApJ 923, 254 (2021)
 [5] Chu et al. PRD 105, 024023 (2022)
 [6] Chatterjee et al. ApJ 896, 54 (2020)
 [7] 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 S230807f (GCN Circular 34360
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 ). 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/S230807f

Based on posterior support from parameter estimation [1], under the assumption that the candidate S230807f 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. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassgap) is <1%.

For the Bilby.offline0.multiorder.fits,0 sky map, the 90% credible region is 5436 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 5272 +/- 1900 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)
 [2] Chatterjee et al. ApJ 896, 54 (2020)

S. Dalessi (UAH) reports on behalf of the Fermi-GBM Team:
 
At 20:50:32.62 on 07 August 2023, the Fermi Gamma-ray Burst Monitor triggered onboard to the event labeled as 713134237 / 230807868 this trigger occurred 15s before the LVK Event S230807f (GCN 34360
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 ). 
 
The trigger is likely due to a solar flare and therefore is not associated to S230807f.