GCN Circular 37694
Subject
GRB 241002B: GOTO24gpc/AT 2024xbg follow-up observations update
Date
2024-10-03T14:14:00Z (3 months ago)
From
Amit Kumar at Royal Holloway - U. of London/U. of Warwick, UK <amitkundu515@gmail.com>
Via
Web form
A. Kumar, D. O'Neill, B. P. Gompertz, G. Ramsay, R. Starling, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, F. Jimenez-Ibarra, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, E. Palle and D. Pollacco report on behalf of the GOTO collaboration:
We report on updated observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) on GRB 241002B (Fermi GBM Team, GCN 37668). Follow-up observations of the GOTO optical counterpart candidate GOTO24gpc/AT2024xbg (Kumar et al. GCN 37676) were performed by GOTO-South at 2024-10-03 09:03:52 UT (t0+26.83h). The observation consisted of 4x90s exposure in the GOTO L-band (400-700 nm).
Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations of the same pointings.
GOTO24gpc/AT2024xbg is not detected down to a 3-sigma limiting magnitude of L > 20.83 mag at t0+26.83h post-trigger. The reported detections of GOTO24gpc/AT2024xbg in g and r bands (20.18 ± 0.3 at t0+6.206h and 19.90 ± 0.25 at t0+6.347h post-trigger, respectively; Torreiro Marinez et al. GCN 37692) are approximately equivalent to an L-band magnitude of ~20.04 ± 0.20 mags, suggesting a decay rate of = t^-0.65±0.29. Fading is further supported by a non-detection in ATLAS observations taken at 20:44:38 UT on 2024-10-02 (t0 + 14.51h) with a 3-sigma limiting magnitude of o > 20.6 mags, consistent with the above decay rate.
We encourage further deeper follow-up observations.
Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are not corrected for Galactic extinction.
GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester and the Instituto de Astrofisica de Canarias (IAC).