GCN Circular 42074
Subject
GRB 251003A: LCOGT Optical Detection
Event
Date
2025-10-03T04:04:06Z (6 days ago)
From
Robert Strausbaugh at Eastern Illinois University <rstrausbaugh@eiu.edu>
Via
email
R. Strausbaugh (Eastern Illinois University), A. Cucchiara (NASA) report on behalf of a larger collaboration:
We observed the Swift GRB 251003A field (Beardmore et al., GCN 42070) with the LCOGT 1-meter Sinistro instrument at the McDonald Observatory, USA site, on October 3, from 03:07 to 03:39 UT (corresponding to 1.15 to 1.68 hours after the GRB trigger time) with the SDSS i and r filters.
We performed a series of 3x300s exposures in i-band and r-band. We detect an uncatalogued source in the XRT enhanced error region (Evans et al. GCNC 42071) consistent with other optical counterpart observations (Aceituno et al., GCN 42072; Méndez et al., GCN 42073) in both bands. We note that the r-i color of this event may indicate a moderate redshift source (z>4).
The following magnitudes are calculated using the PanSTARRS catalog as reference:
r = 20.97 +/- 0.12
i = 19.25 +/- 0.04
These magnitudes are not corrected for galactic extinction.