LIGO/Virgo/KAGRA S241114bi
GCN Circular 38228
Subject
LIGO/Virgo/KAGRA S241114bi: Identification of a GW compact binary merger candidate
Date
2024-11-15T00:25:28Z (6 months ago)
From
Jade Powell at LIGO Scientific Collaboration <jade.powell@ligo.org>
Via
Web form
The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report:
We identified the compact binary merger candidate S241114bi during real-time processing of data from LIGO Livingston Observatory (L1) and Virgo Observatory (V1) at 2024-11-14 23:52:58.148 UTC (GPS time: 1415663596.148). The candidate was found by the GstLAL [1] analysis pipeline.
S241114bi is an event of interest because its false alarm rate, as estimated by the online analysis, is 1.8e-13 Hz, or about one in 1e5 years. The event's properties can be found at this URL:
https://gracedb.ligo.org/superevents/S241114bi
After parameter estimation by RapidPE-RIFT [2], the classification of the GW signal, in order of descending probability, is BBH (91%), NSBH (9%), 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%. [3] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [3] 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 6%.
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 [4], distributed via GCN notice about 27 seconds after the candidate event time.
* bayestar.multiorder.fits,2, 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,2. For the bayestar.multiorder.fits,2 sky map, the 90% credible region is 9934 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 782 +/- 219 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] Rose et al. (2022) arXiv:2201.05263 and Pankow et al. PRD 92, 023002 (2015) doi:10.1103/PhysRevD.92.023002
[3] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe
[4] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013
GCN Circular 38230
Subject
LIGO/Virgo/KAGRA S241114bi: Coverage and upper limits from MAXI/GSC observations
Date
2024-11-15T04:41:09Z (6 months ago)
From
Yuta Kawakubo at Aoyama Gakuin University <kawakubo@phys.aoyama.ac.jp>
Via
Web form
K. Takagi, H. Negoro, M. Nakajima (Nihon U.),
N. Kawai, T. Mihara, (RIKEN),
S. Sugita, M. Serino, Y. Kawakubo, H. Hiramatsu, H. Nishikawa, Y. Kondo (AGU)
report on behalf of the MAXI team:
We examined MAXI/GSC all-sky X-ray images (2-20 keV)
after compact binary merger candidate S241114bi at 2024-11-14 23:52:58.148 UTC (#38228).
At the trigger time of S241114bi, the high-voltage of MAXI/GSC was off,
and it was turned on at T0+792 sec (+13.2 min).
The first one-orbit (92 min) scan observation with GSC after the event covered 94%
of the 90% credible region of the bayestar skymap from 00:06:11 to 01:13:09 UTC (T0+793 to T0+4811 sec).
No significant new source was found in the region in the one-orbit scan observation.
A typical 1-sigma averaged upper limit obtained in one scan observation
is 20 mCrab at 2-20 keV.
If you require information about X-ray flux by MAXI/GSC at specific coordinates,
please contact the submitter of this circular by email.
GCN Circular 38231
Subject
LIGO/Virgo/KAGRA S241114bi: Upper limits from Fermi-GBM Observations
Date
2024-11-15T05:13:30Z (6 months ago)
From
Sarah Dalessi at UAH <sd0104@uah.edu>
Via
Web form
S. Dalessi (UAH) reports on behalf of the Fermi-GBM Team:
For S241114bi (GCN 38228) and using the initial bayestar skymap, Fermi-GBM was observing 59.4% of the localization probability at event time.
There was no Fermi-GBM onboard trigger around the event time of the LIGO/Virgo/KAGRA (LVK) detection of GW trigger S241114bi. An automated, blind search for short gamma-ray bursts below the onboard triggering threshold in Fermi-GBM also identified no counterpart candidates. The GBM targeted search, the most sensitive, coherent search for GRB-like signals, was run from +/-30 s around merger time, and also identified no counterpart candidates.
Part of the LVK localization region is behind the Earth for Fermi, located at an RA=63.3, Dec=4.0 with a radius of 68.0 degrees. We therefore set upper limits on impulsive gamma-ray emission for the GW localization region visible to Fermi at merger time. Using the representative soft, normal, and hard GRB-like templates described in arXiv:1612.02395, we set the following 3 sigma flux upper limits over 10-1000 keV, weighted by GW localization probability (in units of 10^-7 erg/s/cm^2):
Timescale Soft Normal Hard
------------------------------------
0.128 s: 1.2 2.0 3.7
1.024 s: 0.42 0.66 1.2
8.192 s: 0.13 0.18 0.22
Assuming the median luminosity distance of 781.7 Mpc from the GW detection, we estimate the following intrinsic luminosity upper limits over the 1 keV-10 MeV energy range (in units of 10^50 erg/s):
Timescale Soft Normal Hard
------------------------------------
0.128s: 0.14 0.21 0.63
1.024s: 0.047 0.068 0.20
8.192s: 0.015 0.019 0.038
GCN Circular 38243
Subject
LIGO/Virgo/KAGRA S241114bi: Updated Sky localization and EM Bright Classification
Date
2024-11-15T19:53:57Z (6 months ago)
From
Charlie Hoy at University of Portsmouth <charlie.hoy@port.ac.uk>
Via
Web form
The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report:
We have conducted further analysis of the LIGO Livingston Observatory (L1) and Virgo Observatory (V1) data around the time of the compact binary merger (CBC) candidate S241114bi (GCN Circular 38228). 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/S241114bi
Based on posterior support from parameter estimation [1], under the assumption that the candidate S241114bi is astrophysical in origin, the probability that at least one of the compact objects 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 2%.
For the Bilby.offline0.multiorder.fits,0 sky map, the 90% credible region is 10127 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 752 +/- 195 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
[2] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe