GCN Circular 40761
Subject
GRB 250617B: SAO RAS optical observations
Date
2025-06-17T22:54:57Z (21 hours ago)
From
Alexander Moskvitin at SAO RAS <mosk@sao.ru>
Via
Web form
A. Moskvitin, O. Spiridonova, Yu. Sotnikova (SAO RAS),
A. Ghosh, S. Razzaque (CAPP, University of Johannesburg)
We observed the field of the GRB 250617B (Page et al., GCN 40760)
with SAO RAS 1-m telescope Zeiss-1000 equipped with CCD-photometer.
We obtained series of 60, 120 and 300 sec. exposures in Rc band
and also one BVIc series. Observations started on 21:28:06 UT,
since 26 minutes after the trigger.
The OT (Page et al., GCN 40760) is clearly visible in individual images
with the brightness of R = 18.31 +/- 0.04 (t_mid - T0 = 0.5444 hours)
and R = 18.66 +/- 0.04 (t_mid - T0 = 0.7635 hours).
This preliminary photometry is calibrated against R2 magnitudes
of following nearby USNO-B1 stars and not corrected for the Galaxy
extinction.
R.A. Dec. (2000) R2
22:11:38.4 +32:43:48.4 14.880
22:11:19.9 +32:44:17.5 15.280
22:11:41.0 +32:40:41.2 15.070
22:11:45.2 +32:42:19.8 14.690
Observations are ongoing.