GCN Circular 38317
Subject
LIGO/Virgo/KAGRA S241125n: COLIBRÍ Upper Limits on a Optical Counterpart at the BAT Position
Date
2024-11-26T06:20:40Z (a year ago)
From
Alan Watson at UNAM <alan@astro.unam.mx>
Via
email
Alan M. Watson (UNAM), S. Antier (OCA), Stéphane Basa (UAR Pytheas),
William H. Lee (UNAM), D. Akl (AUS), Jean-Luc Atteia (IRAP), Nathaniel R.
Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), J.-G. Ducoin
(CPPM), Simona Lombardo (LAM), Francesco Magnani (CPPM), and Margarita
Pereyra (UNAM) report:
We imaged the field of the Swift/BAT-GUANO candidate counterpart (DeLaunay
et al., GCN Circ. 38308) of the GW compact binary merger candidate S241125n
(LIGO/Virgo/KAGRA Collaborations, GCN Circ. 38305) during the commissioning
of the COLIBRÍ (SVOM/F-GFT) telescope at the Observatorio Astronómico
Nacional on the Sierra de San Pedro Mártir in Mexico.
We observed with the engineering test camera in a red filter that
approximates SDSS r from 2024-11-26 02:08 to 05:49:58 UTC (25.1 to 28.8
hours after the event) and obtained 188 minutes of exposure on a field
about 12 arcmin to a side centered on the BAT position given by DeLaunay et
al. (GCN Circ. 38308). The data were reduced using custom software and then
analysed and calibrated against the PS1 catalog using the STDWeb service.
No clear candidate is identified to a 5-sigma upper limit of
r > 23.0
This limit is below the catalog limit, so definite statements on the
absence of an optical counterpart will require a second epoch of similar
depth.
Further observations are planned.
We warmly thank the COLIBRÍ engineering team and the staff of the
Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir. We
warmly thank the GRANDMA IJCLAB team and S. Karpov for the access of the
STDWeb service for STDPipe.