TITLE: GCN CIRCULAR NUMBER: 39912 SUBJECT: GRB 250327B: LCO optical counterpart detection DATE: 25/03/28 18:04:55 GMT FROM: Ismael Perez-Fournon at Instituto de Astrofisica de Canarias ipf@iac.es
I. Pérez-Fournon, F. Poidevin (IAC and ULL), D. Cano-Morales, I. Correa-Plasencia, A.E. Hernández-Díaz (ULL), and A. López-Oramas (IAC and ULL)
We report Las Cumbres Observatory Global Telescope network (LCOGT) observations of GRB 250327B, detected by SVOM ECLAIRs and MXT (Bouchet et al., GCN circ. 39888) and VT (Xin et al., GCN circ. 39890) and Swift XRT (Page et al., GCN circ. 39895) at a redshift of z = 3.035 (Malesani et. al, GCN circ. 39893; Dennefeld et al., GCN circ. 39905).
We observed the field of GRB 250327B with the two LCOGT 1-m telescopes, equipped with Sinistro cameras, located at the LCOGT node at Teide Observatory (Tenerife, Spain) in the SDSS r, g, and i filters, starting at 2025-03-27 23:55:43 UT, about 2.74 hours after the SVOM trigger. An uncatalogued source is clearly detected at the position of the optical counterpart reported by Moskvitin et al., GCN circ. 39889; Xin et al., GCN circ. 39890; O’Neill et al., GCN circ. 39891; Malesani et al., GCN circ. 39893; Lian et al., GCN circ. 39894; Shrestha et al., GCN circ. 39896; Ducoin et al., GCN circ. 39897; Perley and Bochenek, GCN circ. 39902; Kumar et al., GCN circ. 39904; Dennefeld et al., GCN circ. 39905; and Pankov et al., GCN circ. 39906).
We measure the following magnitudes, calibrated against Pan-STARRS DR2 stars and not corrected for Galactic extinction:
Date | UT start | mag | error | filter | exposure time (sec) --------------------------------------------------------------------- 2025-03-27 23:55:43 18.24 0.02 r 180 2025-03-28 00:31:11 20.07 0.06 g 180 2025-03-28 00:34:41 18.19 0.04 i 180 2025-03-28 02:12:57 18.79 0.06 i 180 2025-03-28 03:04:23 19.35 0.05 r 300 2025-03-28 03:09:13 21.25 0.14 g 180
This work makes use of observations from the Las Cumbres Observatory global telescope network (LCOGT observing programme IAC2025A-009, SGLF).
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