LIGO/Virgo/KAGRA S240830gn
GCN Circular 37354
Subject
LIGO/Virgo/KAGRA S240830gn: Identification of a GW compact binary merger candidate
Date
2024-08-30T21:43:31Z (9 months ago)
Edited On
2024-08-30T22:35:20Z (9 months ago)
From
Brice Williams at LIGO-Hanford/Washington State University <bricemichael.williams@ligo.org>
Edited By
Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov> on behalf of Brice Williams at LIGO-Hanford/Washington State University <bricemichael.williams@ligo.org>
Via
Web form
The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report:
We identified the compact binary merger candidate S240830gn during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2024-08-30 21:11:20.392 UTC (GPS time: 1409087498.392). The candidate was found by the GstLAL [1], MBTA [2], and PyCBC Live [3] analysis pipelines.
S240830gn is an event of interest because its false alarm rate, as estimated by the online analysis, is 6.3e-10 Hz, or about one in 50 years. The event's properties can be found at this URL:
https://gracedb.ligo.org/superevents/S240830gn
The classification of the GW signal, in order of descending probability, is BBH (89%), NSBH (11%), 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%. [4] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [4] 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 8%.
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 [5], distributed via GCN notice about 31 seconds after the candidate event time.
* bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [5], 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 825 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 1236 +/- 337 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] Aubin et al. CQG 38, 095004 (2021) doi:10.1088/1361-6382/abe913
[3] Dal Canton et al. ApJ 923, 254 (2021) doi:10.3847/1538-4357/ac2f9a
[4] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe
[5] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013
GCN Circular 37357
Subject
LIGO/Virgo/KAGRA S240830gn: Updated Sky localization and EM Bright Classification
Date
2024-08-31T00:30:55Z (9 months ago)
From
Soichiro Morisaki at U. of Tokyo <soichiro.morisaki@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 S240830gn (GCN Circular 37354). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.multiorder.fits,0, distributed via GCN Notice, is available for retrieval from the GraceDB event page:
https://gracedb.ligo.org/superevents/S240830gn
Based on posterior support from parameter estimation [1], under the assumption that the candidate S240830gn 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.multiorder.fits,0 sky map, the 90% credible region is 410 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 1118 +/- 297 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. (2023) arXiv:2307.13380
[2] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe
GCN Circular 37358
Subject
LIGO/Virgo/KAGRA S240830gn: Coverage and upper limits from MAXI/GSC observations
Date
2024-08-31T04:54:43Z (9 months ago)
From
Yuta Kawakubo at Aoyama Gakuin University <kawakubo@phys.aoyama.ac.jp>
Via
Web form
Y. Kawakubo, S. Sugita, M. Serino, H. Hiramatsu, H. Nishikawa, Y. Kondo (AGU),
H. Negoro, M. Nakajima, K. Takagi (Nihon U.),
N. Kawai, T. Mihara, (RIKEN),
report on behalf of the MAXI team:
We examined MAXI/GSC all-sky X-ray images (2-20 keV)
after compact binary merger candidate S240830gn at 2024-08-30 21:11:20.392 UTC (GCN #37354, #37357).
At the trigger time of S240830gn, the high-voltage of MAXI/GSC was off,
and it was turned on at T0+374 sec (+6.2 min).
The first one-orbit (92 min) scan observation with GSC after the event covered 65%
of the 90% credible region of the Bilby skymap from 21:31:02 to 22:21:22 UTC (T0+1182 to T0+4202 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.