[vsnet-grb-info 19638] GRB 170728A: LCO observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  21382
SUBJECT: GRB 170728A: LCO observations
DATE:    17/07/29 14:47:33 GMT
FROM:    Antonino Cucchiara at UVI  <antonino.cucchiara at uvi.edu>

A. Cucchiara, D. Morris (U. of Virgin Islands), and
C. Guidorzi (U. Ferrara), reports on behalf of a larger
collaboration:

"On July 28.38 UT  (T_0 +2.1h) we began observing the center
of the field of GRB 170728A (Cannizzo et al. GCN 21367,
Evans et al. GCN 21368) using the Las Cumbres Observatory
1m telescope in Cerro Tololo.
We performed a series of 4x240s observations in R and Ic band
for a total of 16 minutes on sky in each filter at average
airmass of 1.8. Further observations were requested in Sloane
i' filter for a total of 360s.

In the full combined R and I+i' stacks we identified no optical
counterpart within the center of Swift-XRT refined position
(Evans et al. GCN 21368) at the following 3-sigma limits:

R > 18.9 mag
I > 18.4 mag

These magnitudes are calibrated against nearby USNO-B1 sources,
and are not corrected for Galactic extinction."