[vsnet-grb-info 19069] GRB 170205A: NOT afterglow observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  20612
SUBJECT: GRB 170205A: NOT afterglow observations
DATE:    17/02/06 11:00:35 GMT
FROM:    Thomas Kruehler at MPE Garching  <kruehler at mpe.mpg.de>

T. Kruehler (MPE Garching), D. Xu (NAOC,CAS), K. E. Heintz (Univ.
Iceland & DARK/NBI) and G. Fedorets (NOT) report on behalf of the
Nordic GRB collaboration:

We observed the field of GRB 170205A (Troja et al. GCN 20603)
with the NOT equipped with ALFOSC. Photometry in the r and i-band
started at 05:49 UTC on 2017-02-06, 17.2 hr after the GRB trigger,
and was obtained under adverse atmospheric conditions (seeing
around 2.5").

Calibrating our images against magnitudes of field stars from the
SDSS catalog, we measure preliminary brightnesses of the optical
afterglow (Troja et al. GCN 20603, Guidorzi et al. GCN 20605, Butler
et al. GCN 20609) of

r = 22.2 +- 0.2 mag and
i = 22.0 +- 0.2 mag.

These magnitudes are not corrected for the expected foreground
extinction corresponding to a reddening of E_B-V = 0.30 mag
(Schlafly & Finkbeiner 2011).