GCN Circular 18510
Subject
GRB 151027A: LCOGT-McDonald afterglow observations
Date
2015-10-28T12:16:09Z (9 years ago)
From
Cristiano Guidorzi at Ferrara U,Italy <guidorzi@fe.infn.it>
S. Dichiara (U. Ferrara, ICRANet), D. Kopac (U. Ljubljana), C. Guidorzi
(U. Ferrara), S. Kobayashi (LJMU), A. Gomboc (U. Ljubljana) on behalf of
a larger collaboration report:
The 1-m LCOGT McDonald observatory began observing Swift GRB 151027A
(Maselli et al. GCN 18478) on October 28, 01:29:27 UT (0.90 days after
the burst trigger) with SDSS R and I filters. We clearly detect the
optical afterglow (Maselli et al.; Zheng & Filippenko GCN 18479; Elenin
et al. GCN 18480; Perley & Cenko GCN 18481; Xu et al. GCN 18485) with
the following magnitudes:
Mid Time Exposure Filter Magnitude
(days) (s)
-------------------------------------------------------
0.90 5x120 R 16.87 +- 0.04
0.91 6x120 I 17.26 +- 0.05
-------------------------------------------------------
Calibration is done against nearby USNOB-1 star RA(J2000)=18:09:53.742,
DEC(J2000)=+61:20:57.27, assuming R2=17.21 mag and I=17.17 mag. We note
the presence of another USNOB-1 object at RA(J2000)=18:09:56.489,
DEC(J2000)=+61:21:10.64, lying at 3.1 arcsec from the GRB afterglow.