From no-reply@gcn.nasa.gov Mon Nov 25 23:53:39 2024
From: GCN Circulars <no-reply@gcn.nasa.gov>
To: vsnet-grb-info@ooruri.kusastro.kyoto-u.ac.jp
Subject: [vsnet-grb-info 36307] LIGO/Virgo/KAGRA S241125n: Upper limits from
 Fermi-GBM Observations
Date: Mon, 25 Nov 2024 23:53:31 +0000
Message-ID: <0100019365be9ff7-2352d41e-bf35-4ec6-9fdc-12445d0219e7-000000@email.amazonses.com>
MIME-Version: 1.0
Content-Type: multipart/mixed; boundary="===============0458709304826477824=="

--===============0458709304826477824==
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: quoted-printable

TITLE:   GCN CIRCULAR
NUMBER:  38316
SUBJECT: LIGO/Virgo/KAGRA S241125n: Upper limits from Fermi-GBM Observations
DATE:    24/11/25 23:53:23 GMT
FROM:    Lorenzo Scotton at UAH <lscottongcn@outlook.com>

L. Scotton (UAH) reports on behalf of the Fermi-GBM Team:

For LIGO/Virgo/Kagra (LVK) S241125n (GCN 38305) and the Swift/BAT-GUANO candi=
date counterpart (Tohuvavohu, A. et al. 2024, GCN 38308), we used the LVK/BAT=
 combined skymap (combined-ext.multiorder.fits,2; LVK and Swift/BAT, GCN 3831=
5). Fermi-GBM was observing 97.1% of the localization probability at event ti=
me.

There was no Fermi-GBM onboard trigger around the event time of the LVK detec=
tion of GW trigger S241125n. An automated, blind search for short gamma-ray b=
ursts 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 al=
so identified no counterpart candidates.

Part of the LVK-BAT localization region is behind the Earth for Fermi, locate=
d at an RA=3D335.8, Dec=3D12.1 with a radius of 67.7 degrees. We therefore se=
t upper limits on impulsive gamma-ray emission for the LVK-BAT localization r=
egion visible to Fermi at merger time. Using the representative soft, normal,=
 and hard GRB-like templates described in arXiv:1612.02395, we set the follow=
ing 3 sigma flux upper limits over 10-1000 keV, weighted by GW localization p=
robability (in units of 10^-7 erg/s/cm^2):

Timescale  Soft     Normal     Hard   =20
--------------------------------------
0.128 s:   1.7      2.9        5.5=20
1.024 s:   0.6      1.0        1.7=20
8.192 s:   0.2      0.3        0.6=20

Assuming the median luminosity distance of 3213.8 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:    3.3      4.9      15.8
1.024s:    1.3      1.6       4.9
8.192s:    0.4      0.5       1.6


View this GCN Circular online at https://gcn.nasa.gov/circulars/38316.
---
To unsubscribe, open this link in a web browser:
https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LWd=
yYi1pbmZvQG9vcnVyaS5rdXNhc3Ryby5reW90by11LmFjLmpwIiwidG9waWNzIjpbImNpcmN1bGFy=
cyJdLCJpYXQiOjE3MzI1Nzg4MDgsImlzcyI6Imh0dHBzOi8vZ2NuLm5hc2EuZ292In0.1P1LvIMhe=
Ibu8TWu6h4M-b0hspzUBWOh8Xh54dWZpLo

--===============0458709304826477824==--


