[vsnet-grb-info 15366] GRB 140801A: NOT afterglow confirmation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  16656
SUBJECT: GRB 140801A: NOT afterglow confirmation
DATE:    14/08/02 03:34:21 GMT
FROM:    Dong Xu at DARK/NBI  <dong.dark at gmail.com>

D. Xu (DARK/NBI), S. Schulze (PUC, MAS), M. El-Souri, S. Boye Nissen,
M. Sparre, J. P. U. Fynbo (DARK/NBI), A. de Ugarte Postigo (IAA-CSIC,
DARK/NBI), P. Jakobsson (U. Iceland) report on behalf a larger
collaboration:

We observed the field of GRB 140801A (Fermi trigger 428612396) with
the 2.5-m Nordic Optical Telescope (NOT) equipped with ALFOSC. We
obtained a 200-s exposure in each of V, R, and I bands. Observations
started at 01:07:23 UT on August 2 (i.e. 6.12 hours after the burst).

The optical transient reported by Gorbovskoy et al. (GCN 16653) is
clearly detected in each of our images at the same position. And it
has decayed to R(Vega) ~ 20.6 mag at 6.15 hours post-trigger,
calibrated against two bright nearby USNO B1 stars. This measurement
is not corrected for foreground extinction.

The OT roughly decays as t^-1.5 during the MASTER observations (GCN
16653), and then changes to roughly as t^-0.9 assuming a simple
power-law decline since the MASTER's end-time. The whole behavior is
similar to that of previous GRB optical afterglows. We thus conclude
that this OT is very likely the optical afterglow of GRB 140801A.