[vsnet-grb-info 16596] GRB 150527A: LCOGT McDonald observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  17877
SUBJECT: GRB 150527A: LCOGT McDonald observations
DATE:    15/05/27 09:02:38 GMT
FROM:    Cristiano Guidorzi at Ferrara U,Italy  <guidorzi at fe.infn.it>

J. Japelj (U. Ljubljana), C. Guidorzi (U. Ferrara), C.G. Mundell (U. Bath),
S. Kobayashi (LJMU), A. Gomboc (U. Ljubljana) on behalf of a
larger collaboration report:

The 1-m LCOGT McDonald unit began observing Swift GRB 150527A
(Evans al GCN 17874) on May 27 at 06:56:33 UT (~7.6 minutes
after the burst trigger) with SDSS r and i filters.
Inside the Swift-XRT error circle we provide conservative
limits on detection down to the following limiting magnitudes:

Mid Time      Exposure       Filter       Magnitude
(s)           (s)
---------------------------------------------------
  795          5x120          r'           > 19.5
1500          5x120          i'           > 18.3
---------------------------------------------------

These values are compatible with the source reported by RATIR
(Butler et al. GCN 17876), although no information about its
position is reported.
We note the presence of a faint source in our coadded image
with i'=20.6 +- 0.4 mag at the following position:
RA(J2000)=19:15:50.31, Dec(J2000)= +04:12:05.0.
However, we caution that the field is crowded, Galactic
dust extinction towards this field is high, A_V = 2.7 mag
(Schlafly et al. 2011).
Calibration is done against nearby USNOB-1 stars.