TITLE: GCN CIRCULAR NUMBER: 40189 SUBJECT: GRB 250419A: LCO optical observation DATE: 25/04/21 08:35:46 GMT FROM: ankur ghosh at CAPP, University of Johannesburg ghosh.ankur1994@gmail.com
Ankur Ghosh, Soebur Razzaque (CAPP, University of Johannesburg), Alexander Moskvitin, Yulia Sotnikova (SAO RAS), Naveen Dukiya (ARIES), Rahul Gupta (NASA GSFC) on behalf of a larger collaboration.
We observed the field of the GRB 250419A triggered by SVOM/ECLAIRs (Wang et al., GCN 40168) in V, r filters of the 1-meter Sinistro and B filter of 0.4 m SCICAM QHY600 telescopes at the Las Cumbres Observatory Global Telescope (LCOGT) node located at Siding Spring New South Wales, Australia. The 1-m Sinistro telescope is equipped with a 4K x 4K CCD (FOV: 26 x 26 arcmin, scale: 0.39 arcsec/pixel). The 0.4 m SCICAM QHY600 is equipped with 9576 x 6388 pixel CCD (FOV: 1.9 x 1.2 degrees, scale: 0.74 arcsec/pixel) but we only used the FOV of 30 x 30 arcmin for our observation.
Observations began on , starting from 2025-04-19T10:30:01.728 UT, 8.00 hours after the GRB trigger. Observation for later epochs are still going on.
We clearly detect the optical transient (OT) reported by GCNs (López et al., GCN 40169; Xin et al., GCN 40170; Zheng et al., GCN 40171; Kumar et al., GCN 40172; Thakur et al., GCN 40174; Lipunov et al., GCN 40179; Odeh et al., GCN 40180; Perley et al., GCN 40181; Pankov et al., GCN 40182; Pérez-Fournon GCN 40183; Kuin et al., GCN 40185; WU et al., GCN 40186; Xie et al., GCN 40187, Jiang et al., GCN 40188) in our B, V, r band images.
|Date| |UTstart| |t-T0 (hours)| |Exp (sec)| |Filter| |Magnitude| ----------------------------------------------------------------------------------------------------- 2025-04-19 10:30:01.728 8.00 1 x 600 V V = 19.50+/- 0.02 2025-04-19 10:41:55.392 8.21 1 x 600 r r = 19.35+/- 0.01 2025-04-19 14:57:03.744 12.46 2 x 450 B B = 20.51 +/- 0.11 -----------------------------------------------------------------------------------------------------
The field was calibrated against nearby APASS stars, with magnitudes converted using Lupton (2005) equations, and has not been corrected for Galactic extinction.
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