GCN Circular 42287
Subject
GRB 251014B: VLT/FORS2 Optical Observation
Event
Date
2025-10-15T13:01:17Z (2 days ago)
From
Roberto Ricci at INAF-IRA <ricci@ira.inaf.it>
Via
Web form
Muskan Yadav (U Rome), Yu-Han Yang (U Rome), Roberto Ricci (U Rome), Niccolò Passaleva (U Rome), Rosa Becerra (U Rome), Eleonora Troja (U Rome), Lei Hu (Upenn) report on behalf of the ERC BHianca team:
We observed the Swift-BAT/GUANO (Ronchini et al., GCN 42263) field of GRB 251014B detected by Fermi-GBM (trigger number 782110046) with the FORS2 imager on the ESO VLT UT1 (Antu). Observations started on Oct 15th, 2025 at 05:22 UT (24.6 hours after the trigger) and were carried out in the R filter with an average airmass of ~1.06 and exposure time of 20 minutes.
Image subtraction against the SkyMapper Southern Survey (SMSS) Fourth Data Release (DR4) catalog (Onken et., 2024) shows no new uncataloged sources down to a 3-sigma limiting magnitude of ~24 AB mag. Several fainter sources are visible within the XRT localization of source #2 (Evans et al., GCN 42265) within the BAT localization, however they match catalogued counterparts in the Dark Energy Survey (DES) catalogue (DR2; Abbott et al. 2021) and, without a deeper template image, we cannot assess their variability.
We thank the staff at the VLT for the rapid execution of these observations.