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GCN Circular 23867

GRB 190204A: Mondy optical upper limit
2019-02-04T18:55:55Z (5 years ago)
Alina Volnova at SAI MSU <>
A. Volnova (IKI),  A. Pozanenko (IKI),  E. Klunko (ISTP), R. Inasaridze
(AbAO), E. Mazaeva (IKI), S. Belkin (IKI)  report   on behalf of

We observed the field of localization of  GRB 190204A   (Lien et al. GCN
23852)    with AZT-33IK telescope of Sayan observatory (Mondy).   We
started observations on Feb. 04 (UT) 13:10:12 in R-filter. We do not
detect  the optical afterglow (Lien et al.  GCN 23852; Watson et al.,
GCN  23861;  Kuin et al., GCN  23863). Preliminary photometry of the
field is following.

Date               UT start      t-T0          Filter Exp.   OT     Err.
                                         (mid, days)        (s)
                (3 sigma)

2019-02-04  13:10:12  0.32583     R      25*120      n/d     n/d   20.3

The photometry is based on nearby SDSS stars:
SDSS_id                         R_Lupton
J232549.70+545348.8 16.978 0.014
J232550.46+545253.5 17.052 0.014
J232544.33+545253.6 16.085 0.013

Our observation confirm rapid initial decay of the afterglow detected by
UVOT (Kuin et al., GCN  23863).
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