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GCN Circular 21277

GRB 170626A: SAO RAS confirmation of OT fading
2017-06-27T22:58:52Z (7 years ago)
Moskvitin Alexander at SAO RAS <>
A. Moskvitin (SAO RAS), A. Volnova (IKI RAS), A. Pozanenko (IKI RAS),
I. Reva (Fesenkov Astrophysical Institute),
report on behalf of larger GRB follow-up team:

We observed the field of the GRB 170626A (Marshall et al., GCNC 21264)
with the 1-m telescope of SAO RAS, Zeiss-1000 on June, 27.
The OT observed by numerous telescopes (de Ugarte Postigo et al.,
GCNC 21269; Melandri et al., GCNC 21270; Gres et al. GCNC 21272;
Izzo et al., GCNC 21273; Volnova et al., GCNC 21276)
is approx. 0.9 magnitude fainer than in previous SAO epoch.
F ~ (t-T0)^ alpha. The decay slope alpha is about -0.7.

The result of the first SAO epoch (GCNC 21268) were checked with the
full 1.5 hour stack obtained during the first night.
The stacked frames of both epochs were re-calibrated
against all standards mentioned by Volnova et al. (GCNC 21276).
The results are presented in the following table.
The errors are statistical only.

Date       UT start   T_mid - T0, d  Filter Exp., s   mag_OT   Err.

2016.06.26 19:57:42   0.4695         Rc     18 x 300  19.83 +/- 0.04 (GCNC
2016.06.27 18:50:27   1.4079         Rc     12 x 300  20.68 +/- 0.07
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