[vsnet-grb-info 16388] GRB 150323C: Khureltogot optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  17669
SUBJECT: GRB 150323C: Khureltogot optical observations
DATE:    15/04/04 11:07:51 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen at iki.rssi.ru>

E. Mazaeva (IKI), S. Schmalz (AIP), N. Tungalag (Research Center of 
Astronomy and Geophysics MAS),  A. Volnova (IKI), I.Molotov (KIAM), A. 
Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:

We observed the field of the GRB 150323C (Amaral-Rogers  et al., GCN 17621) 
with ORI-40 telescope of Khureltogot observatory starting on Mar., 23 (UT) 
17:20:51, i.e. ~15 minutes after burst trigger. We obtained 180 unfiltered 
images of 60 s exposure. Within  enhanced Swift-XRT error circle (Osborne et 
al., GCN 17633)  we detect optical afterglow (Xu et al. GCN 17625, Xin et 
al. GCN 17631; Watson et al. GCN 17632). Preliminary photometry of the 
afterglow in combined images is following

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

2015-01-23  17:20:51  0.01449   none    10*60  21.1 0.3
2015-01-23  17:31:40  0.02199   none    10*60  20.5 0.25
2015-01-23  17:42:28  0.02950   none    10*60  20.8 0.25
2015-01-23  17:53:17  0.03700   none    10*60  20.2 0.2
2015-01-23  18:04:04  0.04451   none    10*60  20.0 0.2
2015-01-23  18:14:54  0.06199   none    35*60  21.3 0.3
2015-01-23  18:54:26  0.09409   none    39*60  21.0 0.3
2015-01-23  19:57:04  0.13649   none    40*60  21.5 0.4

Photometry is based on SDSS DR9 stars:

SDSS9_id                        R(Lupton)
J125026.13+501147.9  16.16
J125023.08+501048.2  16.84

Our photometry confirms  non-monotonic behaiviour of a lighr curve of the 
afterglow mentioned by Xin et al. (GCN 17631).
The light curve of GRB 150323C afterglow can be found in 
http://grb.rssi.ru/GRB150323C/GRB150323C_ORI40_lc.png