TITLE: GCN CIRCULAR NUMBER: 36676 SUBJECT: GRB 240615A: GOTO optical upper limits DATE: 24/06/16 08:59:28 GMT FROM: Amit Kumar at University of Warwick, UK amitkundu515@gmail.com
A. Kumar; B. P. Gompertz; G. Ramsay; S. Belkin; R. Starling; D. K. Galloway; K. Ackley; M. J. Dyer; J. Lyman; K. Ulaczyk; F. Jimenez-Ibarra; D. O'Neill; D. Steeghs; 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 optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022) in response to the Fermi GBM detected GRB 240615A (Fermi GBM Team, GCN 36671). Targeted observations also covered the Swift/BAT-GUANO updated localisation (DeLaunay, et al., GCN 36672) with GOTO-N on 2024-06-16 from UT 01:39:52 to 03:56:07 (from ~7.80 to 10.07 hours after trigger, respectively) distributed over four epochs. Each observation consisted of 4x90s exposures in the GOTO L-band (400-700 nm).
Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using recent survey observations of the same pointings. Source candidates were initially filtered using a classifier (Killestein et al. 2021) and cross-matched against a variety of contextual and minor planet catalogs. Human vetting was carried out in real time on any candidates that passed the above checks.
No significant optical counterpart is detected within the Swift/BAT-GUANO localisation region to a 5-sigma limiting L-band magnitude range of 19.8-20.4 (AB) across 4 epochs of 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).
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