TITLE: GCN CIRCULAR NUMBER: 39759 SUBJECT: EP 250317B: Fading optical counterpart detection by LCO DATE: 25/03/17 11:21:28 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 250317B triggered by SVOM/ECLAIRs (Zhao et al., GCN circ. 39752 and GCN circ. 39753) and SVOM/MXT(Zhao et al., GCN circ. 39752 and GCN circ. 39753; and Götz et al., GCN circ. 39756) in r filter of the 0.4-m SCICAM QHY600 at the Las Cumbres Observatory Global Telescope (LCOGT) node located at Haleakala Observatory, Hawai . 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 March 17, 2025, starting 6.46 hours after the GRB trigger.
We clearly detect the optical transient (OT) reported by GCNs (Watson et al., GCN circ. 39754, Palmerio et al., GCN circ. 39755, Pérez-Fournon et al., GCN 39757) in our r band image.
|Date| |UTstart| |t-T0 (hours)| |Exp (sec)| |Filter| |Magnitude| -------------------------------------------------------------------------------------------------- 2025-03-17 08:39:27.93 6.46 2 x 300 r r = 19.48 +/- 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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