D. Xu (NAOC/CAS), A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), N. R.
Tanvir (Univ. Leicester), D. Malesani (DARK/NBI), T. Kruehler (MPE),
P. Jakobsson (Univ. Iceland), S. Schulze (PUC, MAS), V. D'Elia
(ASI/ASDC and INAF-OAR), K. Karhunen (Turku Univ.), report on behalf
of a larger collaboration:
We observed the field of GRB 150915A (D'Elia et al., GCN 18315) with
the Nordic Optical Telescope equipped with the ALFOSC camera. Two
observations composed each by 3x300 s exposures in R-band were taken
with the mean times of 0.80 and 3.05 hr after the GRB trigger.
The source detected by GROND and reported by Yates et al. (GCN 18317)
is clearly visible in our images at both epochs, with a magnitude of
R(Vega) = 22.52 +- 0.09 on our first epoch (assuming R = 16.72 for the
star at RA = 21:18:34.76, Dec = -34:53:44.9).
Interestingly, the object is found to brighten between the two epochs
by 0.28 +- 0.11 mag - a behavior not common, though not unprecedented.