TITLE: GCN CIRCULAR NUMBER: 40082 SUBJECT: GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations. DATE: 25/04/05 22:22:30 GMT FROM: Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, Messina, Italy giovannicalapai@tiscali.it
Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, (Messina) Italy Member of: GRB/UAI Gamma Ray Burst Section of Unione Astrofili Italiani.
Report:
We observed the field of GRB 250402A (SVOM burst-id sb25040203, Chen et al., GCN 40014) with the 11 inches Schmidt-Cassegrain (Celestron 11) telescope F/D=6,3.
The observations were started at 2025-04-02 23:57 UT (approximately 49 min after burst) stacking a set of unfiltered CCD image. The observations were carried out with clear skies and fair visibility conditions.
The OT was detected at the following position (+/- 0.3 arcsec):
RA (J2000.0) 14h 13m 38.17s Decl. (J2000.0) -05° 55' 48.8"
Photometry was obtained using nearby PanSTARRS stars as follows:
Observation Mid-Time T-T0 (hr) Exposure Filter Mag. Err. 2025-04-03 01:39:02 UT 2.52 180x60s CR 21.6 +/- 0.4
Magnitude was calibrated with the nearby PanSTARRS stars converted using Lupton (2005) equations. No correction for galactic dust extinction was applied.
Our observations are consistent with other already reported L.P. Xin et al. (GCN 40015), Pérez-Fournon et al. (GCN 40020), Brivio et al. (GCN 40021), Schneider et al. (GCN 40022), Magnani et al. (GCN 40023), Komesh et al. (GCN 40033), Shilling et al. (GCN 40047), Mazaeva et al. (GCN 40049).
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