LIGO/Virgo/KAGRA S241109bn
GCN Circular 38142
Subject
LIGO/Virgo/KAGRA S241109bn: Identification of a GW compact binary merger candidate
Date
2024-11-09T12:36:57Z (7 months ago)
From
Biswajit Banerjee at Gran Sasso Science Institute (GSSI) <biswajit.banerjee@gssi.it>
Via
Web form
The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report:
We identified the compact binary merger candidate S241109bn during real-time processing of data from LIGO Hanford Observatory (H1) and Virgo Observatory (V1) at 2024-11-09 11:59:24.899 UTC (GPS time: 1415188782.899). The candidate was found by the GstLAL [1], MBTA [2], and PyCBC Live [3] analysis pipelines.
S241109bn is an event of interest because its false alarm rate, as estimated by the online analysis, is 1.4e-11 Hz, or about one in 1e3 years. The event's properties can be found at this URL:
https://gracedb.ligo.org/superevents/S241109bn
The initial classification of the GW signal, based on chirp-mass information only [3], in order of descending probability, is NSBH (62%), BBH (38%), 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 21%. [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 for maximum neutron star mass. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is 83%.
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 24 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 10353 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 583 +/- 171 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 38143
Subject
LIGO/Virgo/KAGRA S241109bn: Global MASTER-Net observations report
Date
2024-11-09T13:10:58Z (7 months ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
legacy email
V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko,
A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin,
V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU),
O.Gress, N.Budnev (ISU),
C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity)
D.Buckley (SAAO),
R.Rebolo (The Instituto de Astrofisica de Canarias),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)
MASTER-Tunka robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the LIGO/Virgo/KAGRA S241109bn errorbox 16 sec after trigger time at 2024-11-09 11:59:40 UT, with upper limit up to 19.9 mag. The observations began at zenith distance = 60 deg. The sun altitude is -24.0 deg.
The galactic latitude b = -22 deg., longitude l = 314 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/ligo_1.php?id=23757
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
46 | 2024-11-09 11:59:40 | MASTER-Tunka | (03h 17m 17.41s , +29d 28m 17.8s) | C | 60 | 18.7 |
119 | 2024-11-09 12:00:52 | MASTER-Tunka | (03h 08m 12.16s , +29d 28m 34.7s) | C | 60 | 19.3 |
197 | 2024-11-09 12:02:11 | MASTER-Tunka | (03h 17m 20.04s , +29d 30m 10.6s) | C | 60 | 19.6 |
270 | 2024-11-09 12:03:24 | MASTER-Tunka | (03h 08m 08.76s , +29d 28m 31.1s) | C | 60 | 19.6 |
358 | 2024-11-09 12:04:52 | MASTER-Tunka | (06h 50m 17.97s , +54d 17m 35.7s) | C | 60 | 19.3 |
418 | 2024-11-09 12:04:52 | MASTER-Tunka | (06h 50m 17.97s , +54d 17m 35.7s) | C | 180 | 19.9 | Coadd
441 | 2024-11-09 12:06:14 | MASTER-Tunka | (07h 04m 01.27s , +54d 19m 14.3s) | C | 60 | 19.4 |
501 | 2024-11-09 12:06:14 | MASTER-Tunka | (07h 04m 01.27s , +54d 19m 14.3s) | C | 180 | 19.8 | Coadd
525 | 2024-11-09 12:07:39 | MASTER-Tunka | (03h 17m 24.44s , +29d 29m 23.9s) | C | 60 | 19.7 |
585 | 2024-11-09 12:07:39 | MASTER-Tunka | (03h 17m 24.43s , +29d 29m 23.9s) | C | 180 | 19.9 | Coadd
599 | 2024-11-09 12:08:52 | MASTER-Tunka | (03h 08m 06.68s , +29d 28m 20.6s) | C | 60 | 19.7 |
659 | 2024-11-09 12:08:52 | MASTER-Tunka | (03h 08m 06.68s , +29d 28m 20.5s) | C | 180 | 19.7 | Coadd
685 | 2024-11-09 12:10:18 | MASTER-Tunka | (06h 50m 24.29s , +54d 16m 39.7s) | C | 60 | 19.3 |
758 | 2024-11-09 12:11:31 | MASTER-Tunka | (07h 04m 05.00s , +54d 18m 57.3s) | C | 60 | 19.5 |
844 | 2024-11-09 12:12:58 | MASTER-Tunka | (03h 17m 20.88s , +29d 28m 58.5s) | C | 60 | 18.8 |
917 | 2024-11-09 12:14:11 | MASTER-Tunka | (03h 08m 12.30s , +29d 30m 19.5s) | C | 60 | 16.9 |
1002 | 2024-11-09 12:15:35 | MASTER-Tunka | (06h 50m 19.98s , +54d 17m 28.4s) | C | 60 | 19.4 |
1085 | 2024-11-09 12:16:58 | MASTER-Tunka | (04h 03m 15.82s , +52d 17m 44.6s) | C | 60 | 18.7 |
1145 | 2024-11-09 12:16:58 | MASTER-Tunka | (04h 03m 15.82s , +52d 17m 44.6s) | C | 180 | 19.0 | Coadd
1158 | 2024-11-09 12:18:12 | MASTER-Tunka | (04h 16m 14.49s , +52d 17m 01.7s) | C | 60 | 18.6 |
1238 | 2024-11-09 12:19:32 | MASTER-Tunka | (03h 17m 23.75s , +29d 28m 36.6s) | C | 60 | 19.0 |
1311 | 2024-11-09 12:20:45 | MASTER-Tunka | (03h 08m 09.79s , +29d 30m 04.7s) | C | 60 | 19.4 |
1389 | 2024-11-09 12:22:02 | MASTER-Tunka | (04h 03m 13.82s , +52d 17m 17.8s) | C | 60 | 17.6 |
1463 | 2024-11-09 12:23:16 | MASTER-Tunka | (04h 16m 22.30s , +52d 18m 59.7s) | C | 60 | 16.6 |
1526 | 2024-11-09 12:24:20 | MASTER-Tunka | (03h 17m 18.98s , +29d 29m 37.5s) | C | 60 | 19.3 |
1599 | 2024-11-09 12:25:33 | MASTER-Tunka | (03h 08m 08.00s , +29d 30m 36.0s) | C | 60 | 19.7 |
1676 | 2024-11-09 12:26:50 | MASTER-Tunka | (04h 03m 17.81s , +52d 17m 54.6s) | C | 60 | 18.5 |
1933 | 2024-11-09 12:31:06 | MASTER-Tunka | (07h 04m 09.13s , +54d 18m 36.6s) | C | 60 | 18.4 |
2018 | 2024-11-09 12:32:32 | MASTER-Tunka | (03h 17m 22.12s , +29d 29m 05.6s) | C | 60 | 19.8 |
2093 | 2024-11-09 12:33:46 | MASTER-Tunka | (03h 08m 12.87s , +29d 30m 26.8s) | C | 60 | 19.8 |
2177 | 2024-11-09 12:35:11 | MASTER-Tunka | (07h 04m 07.96s , +54d 17m 51.9s) | C | 60 | 17.4 |
2237 | 2024-11-09 12:35:11 | MASTER-Tunka | (07h 04m 07.97s , +54d 17m 51.9s) | C | 180 | 17.6 | Coadd
2249 | 2024-11-09 12:36:22 | MASTER-Tunka | (07h 04m 08.18s , +54d 18m 51.8s) | C | 60 | 16.7 |
2322 | 2024-11-09 12:37:35 | MASTER-Tunka | (06h 50m 31.54s , +54d 17m 14.9s) | C | 60 | 17.6 |
2382 | 2024-11-09 12:37:35 | MASTER-Tunka | (06h 50m 31.54s , +54d 17m 14.9s) | C | 180 | 17.7 | Coadd
2395 | 2024-11-09 12:38:49 | MASTER-Tunka | (06h 50m 25.08s , +54d 16m 13.8s) | C | 60 | 16.8 |
2467 | 2024-11-09 12:40:00 | MASTER-Tunka | (06h 50m 32.11s , +54d 16m 31.8s) | C | 60 | 16.5 |
2547 | 2024-11-09 12:41:21 | MASTER-Tunka | (04h 16m 22.23s , +52d 18m 52.2s) | C | 60 | 19.0 |
2621 | 2024-11-09 12:42:35 | MASTER-Tunka | (04h 16m 22.42s , +52d 17m 22.2s) | C | 60 | 18.9 |
2681 | 2024-11-09 12:42:35 | MASTER-Tunka | (04h 16m 22.42s , +52d 17m 22.1s) | C | 180 | 19.6 | Coadd
2693 | 2024-11-09 12:43:46 | MASTER-Tunka | (04h 16m 26.54s , +52d 19m 08.7s) | C | 60 | 18.5 |
2767 | 2024-11-09 12:45:01 | MASTER-Tunka | (04h 03m 14.18s , +52d 18m 07.5s) | C | 60 | 18.5 |
2827 | 2024-11-09 12:45:01 | MASTER-Tunka | (04h 03m 14.18s , +52d 18m 07.5s) | C | 180 | 19.0 | Coadd
2838 | 2024-11-09 12:46:12 | MASTER-Tunka | (04h 03m 13.71s , +52d 19m 08.9s) | C | 60 | 17.5 |
2911 | 2024-11-09 12:47:25 | MASTER-Tunka | (04h 03m 20.25s , +52d 18m 10.4s) | C | 60 | 18.8 |
3096 | 2024-11-09 12:50:29 | MASTER-Tunka | (07h 04m 15.57s , +54d 17m 17.7s) | C | 60 | 16.8 |
3169 | 2024-11-09 12:51:42 | MASTER-Tunka | (07h 04m 13.39s , +54d 18m 36.3s) | C | 60 | 18.0 |
3244 | 2024-11-09 12:52:58 | MASTER-Tunka | (07h 04m 13.65s , +54d 16m 54.5s) | C | 60 | 19.1 |
3325 | 2024-11-09 12:54:19 | MASTER-Tunka | (04h 16m 27.69s , +52d 19m 18.9s) | C | 60 | 19.4 |
3400 | 2024-11-09 12:55:34 | MASTER-Tunka | (04h 16m 21.11s , +52d 18m 32.8s) | C | 60 | 19.5 |
3474 | 2024-11-09 12:56:48 | MASTER-Tunka | (04h 16m 20.44s , +52d 19m 34.4s) | C | 60 | 19.5 |
3554 | 2024-11-09 12:58:07 | MASTER-Tunka | (06h 07m 40.88s , +52d 20m 32.2s) | C | 60 | 19.3 |
3626 | 2024-11-09 12:59:20 | MASTER-Tunka | (06h 20m 54.32s , +52d 21m 03.6s) | C | 60 | 19.4 |
3700 | 2024-11-09 13:00:33 | MASTER-Tunka | (06h 07m 44.43s , +52d 22m 11.8s) | C | 60 | 19.3 |
3779 | 2024-11-09 13:01:53 | MASTER-Tunka | (06h 20m 51.01s , +52d 21m 03.6s) | C | 60 | 19.3 |
3853 | 2024-11-09 13:03:06 | MASTER-Tunka | (06h 07m 48.85s , +52d 22m 12.7s) | C | 60 | 19.3 |
3958 | 2024-11-09 13:04:51 | MASTER-Tunka | (06h 24m 27.80s , +54d 17m 07.5s) | C | 60 | 19.5 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 38146
Subject
LIGO/Virgo/KAGRA S241109bn: Upper limits from Fermi-GBM Observations
Date
2024-11-09T20:18:17Z (7 months ago)
From
Utkarsh Pathak at IIT Bombay <utkarshpathak.07@gmail.com>
Via
Web form
U. Pathak (IITB) reports on behalf of the Fermi-GBM Team:
For S241109bn (GCN 38142) and using the update bayestar skymap, Fermi-GBM was observing 71.8% 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 S241109bn. 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=229.0, Dec=-22.5 with a radius of 67.7 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 4.6
1.024 s: 0.34 0.59 1.2
8.192 s: 0.13 0.24 0.53
Assuming the median luminosity distance of 602.6 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: 0.080 0.122 0.466
1.024s: 0.023 0.036 0.122
8.192s: 0.009 0.015 0.054
GCN Circular 38149
Subject
LIGO/Virgo/KAGRA S241109bn: Updated Sky localization and EM Bright Classification
Date
2024-11-09T23:38:36Z (7 months ago)
From
Aditya Vijaykumar <aditya.vijaykumar@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) and Virgo Observatory (V1) data around the time of the compact binary merger (CBC) candidate S241109bn (GCN Circular 38142). 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/S241109bn
Based on posterior support from parameter estimation [1], under the assumption that the candidate S241109bn is astrophysical in origin, the probability that at least one of the compact objects is consistent with a neutron star (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 43%.
Preliminary information from parameter estimation seems to indicate a much smaller NSBH probability than initially reported (GCN Circular 38142), and almost certainly a BBH origin.
For the Bilby.offline0.multiorder.fits,0 sky map, the 90% credible region is 10138 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 603 +/- 159 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/ab8dbez
GCN Circular 38151
Subject
LIGO/Virgo/KAGRA S241109bn: Coverage and upper limits from MAXI/GSC observations
Date
2024-11-10T03:10:03Z (7 months ago)
From
Motoko Serino at Aoyama Gakuin U. <serino@phys.aoyama.ac.jp>
Via
Web form
Y. Kondo, S. Sugita, M. Serino, Y. Kawakubo, H. Hiramatsu, H. Nishikawa (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 S241109bn at 2024-11-09 11:59:24.899 UTC (GCN 38142, 38149).
At the trigger time of S241109bn, the high-voltage of MAXI/GSC was on.
The instantaneous field of view of GSC at the GW trigger time covered 1% of the 90% credible region
of the Bilby sky map, in which we found no significant new X-ray source.
The first one-orbit (92 min) scan observation with GSC after the event covered 68%
of the 90% credible region of the Bilby skymap from 11:59:24 to 13:31:23 UTC (T0+0 to T0+5519 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 38154
Subject
LIGO/Virgo/KAGRA S241109bn: Upper limits from EP-WXT observations
Date
2024-11-10T08:29:31Z (7 months ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
X. Mao (NAO, CAS), A. Li (BNU), C. Y. Wang (THU), X. L. Chen, Kaushik Chatterjee (YNU), M. H. Zhang, J. W. Hu, M. Zhang and Y. Liu (NAO, CAS) report on behalf of the Einstein Probe team:
After the trigger of the gravitational-wave (GW) event S241109bn (LVK Collaboration, GCN 38142), we examined the data of Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP). The 90% credible region of the GW event was occulted by the earth until about 20 minutes after the GW trigger time. The field of view of WXT covered 4.4% of the 90% credible region of the event (598 square degrees) with a duration of about 200 s. The 5-sigma upper limit of the observation in 0.5-4 keV is around 9 x 10^(-11) erg/cm^2/s.
Two target-of-opportunity observations by WXT was carried out about 30 minutes and 2 hours after the trigger, beginning at 2024-11-09 12:28:01 (UTC) and 2024-11-09 14:04:15 (UTC) and lasting for around 2800 s and 2400 s, respectively. 59.2% of the 90% credible region of the event was covered by these two observations, with a total area of 5811 square degrees. No new X-ray source is found in these observations. These two observations set 5-sigma upper limits on the 0.5-4 keV flux in the credible region to be approximately 1.3 x 10^(-11) erg/cm^2/s and 1.4 x 10^(-11) erg/cm^2/s, respectively. For queries on more information about these observations and the upper limits, please contact Xuan Mao at the EP science center (ep_ta@nao.cas.cn).
Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with onboard X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). EP is an international collaborative mission led by the Chinese Academy of Sciences (CAS) and participated by the European Space Agency (ESA), the Max-Planck Institute for Extraterrestrial Physics (MPE) in Germany and the Centre National d’Etudes Spatiales (CNES) in France.
GCN Circular 38168
Subject
LIGO/Virgo/KAGRA S241109bn: ATLAS observations and discovery of the potential counterpart AT2024aawt
Date
2024-11-11T17:51:56Z (7 months ago)
From
James Gillanders at University of Oxford <jhgillanders.astro@gmail.com>
Via
Web form
J. H. Gillanders (Oxford), K. W. Smith, S. J. Smartt (Oxford/QUB), D. R. Young, M. Nicholl, M. Fulton, M. McCollum, T. Moore, J. Weston, X. Sheng, A. Aamer, C. R. Angus, D. Magill (QUB), P. Ramsden (QUB/Birmingham), L. Shingles (GSI/QUB), S. Srivastav, H. Stevance, A. J. Cooper, F. Stoppa (Oxford), L. Rhodes (TSI/McGill), L. Denneau, J. Tonry, H. Weiland, R. Siverd (IfA, University of Hawaii), N. Erasmus, W. Koorts (South African Astronomical Observatory), A. Jordan, V. Suc (UAI, Obstech), A. Rest (STScI), T.-W. Chen (NCU), C. Stubbs (Harvard), J. Sommer (LMU) and B. P. Schmidt (ANU).
We report observations of the skymap of the possible NSBH merger event S241109bn (LVK Collaborations, GCN 38142) with the ATLAS survey (Tonry et al., 2018, PASP, 13, 164505). ATLAS scans the visible night sky every 24-48 hours with a 4x30s tiling pattern, reaching typical limiting magnitudes, m~19.5 (AB mag) in 30 seconds.
Our standard observing strategy tiled 31.7% of the 90% bilby.fits sky localisation area within 24 hours of the GW trigger. This rose to 35.7% within 72 hours. The images were processed with the ATLAS pipeline, and reference images were subtracted. Transient candidates were identified and run through our standard filtering procedures (Smith et al., 2020, PASP, 132, 1). All potential transients that passed our data processing cuts were manually inspected, and cross-matched with catalogued galaxies and stars. We do not find any compelling candidates that lie within the skymap, occurred after the GW trigger time, and are matched with galaxies in the range 0.10 < z < 0.17 (D = 600 +/- 150 Mpc; LVK Collaborations, GCN 38149), to a limit of around m_o~19.5 (AB mag).
We identity one bright transient discovered in images taken 1.57 days after the GW trigger (MJD 60623.50) and registered as AT2024aawt on the IAU Astronomical Transient Name Server (Tonry et al., TNS Astronomical Transient Report No. 232251). We detected the transient at MJD 60625.07 == 2024-11-11 01:40 UTC, at the coordinate location of RA=314.464552727, Dec=-41.64411. Its location is not coincident with any known, catalogued source, although some faint excess is visible in the public DECaLS image of the field. AT2024aawt was discovered with an o-band magnitude, m_o = 17.28 +/- 0.08 (AB mag). Our most recent previous observation at the transient location was on MJD 60624.04 (0.54 days after GW trigger), from which we extracted a 3-sigma limiting magnitude, m_o = 19.50 (AB mag). Forced photometry at the transient location indicates no significant activity for the last 30 days. This is most likely a foreground, Galactic source (such as a dwarf nova in outburst), and thus not related to the GW event, but a spectrum should be taken to confirm.
The Asteroid Terrestrial-impact Last Alert System (ATLAS) project is primarily funded to search for Near-Earth asteroids through NASA grants NN12AR55G, 80NSSC18K0284, and 80NSSC18K1575; by-products of this search include images and catalogues from the survey area. This work was partially funded by Kepler/K2 grant J1944/80NSSC19K0112, HST GO-15889, and STFC grants ST/T000198/1 and ST/S006109/1. The ATLAS science products have been made possible through the contributions of the University of Hawaii’s Institute for Astronomy, Queen's University Belfast, the Space Telescope Science Institute, the South African Astronomical Observatory, and The Millennium Institute of Astrophysics (MAS), Chile.
GCN Circular 38310
Subject
LIGO/Virgo/KAGRA S241109bn: Upper limits from a two-week IceCube neutrino search
Date
2024-11-25T20:38:29Z (6 months ago)
From
Jessie Thwaites at IceCube/U Wisc-Madison <thwaites@wisc.edu>
Via
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IceCube Collaboration (http://icecube.wisc.edu/) reports:
IceCube has performed an additional search [1] for track-like muon neutrino events consistent with the sky localization of gravitational-wave candidate S241109bn in a time range of -0.1 day, +14 days from the alert event time (2024-11-09 09:35:24.899 UTC to 2024-11-23 11:59:24.899 UTC).
During this time period IceCube was collecting good quality data. In this case, we report a p-value of 0.84, consistent with no significant excess of track events. IceCube's sensitivity assuming an E^-2 spectrum (E^2 dN/dE) to neutrino point sources within the locations spanned by the 90% spatial containment of the 4-Update map ranges from 0.028 to 1.219 GeV cm^-2 in this time window.
The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc@icecube.wisc.edu.
[2] Abbasi et al. Astrophys.J. 944 (2023) 1, 80