[vsnet-grb-info 15948] GRB 141225A: Nanshan very early optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  17236
SUBJECT: GRB 141225A: Nanshan very early optical observations
DATE:    14/12/26 06:39:37 GMT
FROM:    Dong Xu at DARK/NBI  <dong.dark at gmail.com>

D. Xu (DARK, NAOC) and X. Gao (Urumqi No.1 Senior High School, Xinjiang) report:

We observed the field of GRB 141225A (D'Avanzo et al., GCN 17229)
using the 36cm robotic telescope located at Nanshan, Xinjiang, China.
Observations started at 23:04:14 UT on 2014-12-25, i.e., 187 s after
the burst, and subsequently 3x40s, 4x60s, and 12x90s unfiltered images
were obtained.

The optical afterglow (Gorosabel et al., GCN 17230; Guidorzi et al.,
GCN 17231; Malesani et al., GCN 17232; Kuin & D'Avanzo, GCN 17233) is
detected in all 40s and 60s exposures and only in the beginnings of
90s exposures, and is evident of decaying. The afterglow has m(R)~17.2
from the first 40s image (i.e., 187 s - 227 s post-burst), calibrated
with R-band magnitudes of nearby SDSS stars.