[vsnet-grb-info 19673] GRB 170804A: LCO Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  21417
SUBJECT: GRB 170804A: LCO Observations
DATE:    17/08/05 16:53:45 GMT
FROM:    Antonino Cucchiara at UVI  <antonino.cucchiara at uvi.edu>

A. Cucchiara, D. Morris (U. of the Virgin Islands), and
N. Orange (OrangeWave), report on behalf of a larger
collaboration:

"On August 4.79 UT  (T_0 +7.0h) we began observing the
center of the field of GRB 170804A (Cholden-Brown et al.
GCN 21410, Emery et al. GCN 21411) using the Las Cumbres
Observatory 1m telescope located in Siding Spring
Observatory.

Under poor sky conditions (seeing ~2.6 arcseconds) we
performed a series of 5x240s observations in SDSS r' and i’
bands for a total of 20 minutes on sky in each filter at
average airmass of 1.3.

In the full median stacked images we identified no optical
counterpart within the center of the Swift-XRT refined position
or at the UVOT optical counterpart location (Evans et al.
GCN 21413, Emery et al. GCN 21411) at the following
3-sigma limits:

r' > 21.4 mag
i' > 21.1 mag

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