GCN Circular 41000
Subject
GRB 250706A: SAO RAS optical observations
Event
Date
2025-07-07T03:57:27Z (17 hours ago)
From
Alexander Moskvitin at SAO RAS <mosk@sao.ru>
Via
Web form
A. Moskvitin and O. Spiridonova (SAO RAS),
report on behalf of a GRB follow-up collaboration.
We observed the field of the GRB 250706A (Moss et al., GCN 40988)
with SAO RAS 1-m telescope Zeiss-1000 equipped with CCD-photometer.
We obtained 20 x 300 sec. images in Rc band on July 6,
20:04:37--22:41:35 UT (t_mid - T0 = 5.5764 hours) under a good weather
conditions and the seeing of 1".6.
In the XRT error circle (Moss et al., GCN 40988) we detected a bright
stellar-like source with the coordinates R.A. = 18:56:04.3,
Dec. = +32:19:13.5 (J2000.0) also presented in the archival images.
After the PSF subtraction of this bright star we did not detect any
significant sources down to the limiting magnitude of R_lim = 23.0.
(based on the nearby USNO-B1.0 stars and not corrected
for the Galactic extinction)
Additionaly we divided whole set into two 10 x 300 sec. subsets
(1st: t_mid - T0 = 4.9217 hours, 2nd: t_mid - T0 = 6.2393 hours)
and found no significant residuals between two stacked images
and no variability of the mentioned bright star within 0.01 mag.
between two epochs.
This results are in agreement with OT non-detection by Moss et al.
(GCN 40988); Mohan et al. (GCN 40990) and Wu et al. (GCN 40998).