GCN Circular 35050

K. Ackley, D. Steeghs, B. P. Gompertz, A. J. Levan, D. B. Malesani, R. Starling, M. J. Dyer, J. Lyman, K. Ulaczyk, F. Jimenez-Ibarra, A. Kumar, D. O'Neill, D. K. Galloway, V. Dhillon, P. O'Brien; G. Ramsay, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, E. Pall'e and D. Pollacco report on behalf of the GOTO collaboration:

The Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022) serendipitously covered the field of GRB 231115A (Fermi GBM Team, GCN 35035
Not found
 
 
; Mereghetti et al, GCN 35037
Not found
 
 
; Cheung et al. GCN 35045
Not found
 
 
) at 04:44:17 UT on 2023-11-15. This is 10.87 hours before trigger and 16.9 hours later than the limits reported in Ahumada et al. (GCN 25048
Not found
 
 
). The observation consisted of a 12x60s exposure set in the GOTO L-band (400-700 nm).

Analysis at the location of the potential optical transient https://www.wis-tns.org/object/2023xvj (Kumar et al. GCN 35041
Not found
 
 
) does not show evidence of the source to a 3-sigma limiting AB magnitude of L > 20.1.

Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed manually on the stacked set using recent survey observations of the same pointings. 

Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are not corrected for Galactic extinction.

Further observations are scheduled during the coming nights.

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).