[vsnet-grb-info 17337] GRB151215A: Early optical light curve from pt5m, La Palma

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  18703
SUBJECT: GRB151215A: Early optical light curve from pt5m, La Palma
DATE:    15/12/16 15:03:14 GMT
FROM:    Liam K Hardy at U of Shffield  <liam.hardy at sheffield.ac.uk>

L. K. Hardy (Sheffield), S. P. Littlefair (Sheffield),
V. S. Dhillon (Sheffield, IAC), T. Butterley (Durham) and
R. W. Wilson (Durham) report:

The automated robotic telescope 'pt5m' (Hardy et al.
2015, MNRAS 454, 4316) on La Palma observed the field
of GRB 151215A (Gibson et al., GCN 18691) starting
at 03:02:42 UT on Dec 15, 53 seconds after the alert
notice release and 74 seconds after the GRB detection.

Observations comprised of 59 x 60-second exposures in
the Johnson/Cousins R-band with approximately 6-seconds
dead time between images. The final image was taken 65
minutes after the first.

We detect the optical counterpart to the GRB and observe a
rapidly declining light curve. Photometry is performed using
historical instrumental zeropoints. We measure an initial
magnitude of R = 17.13 +/- 0.04 (2 minutes after the GRB) and
a final magnitude of R = 20.8 +/- 0.7 (67 minutes after the GRB).

The light curve is available at:
http://slittlefair.staff.shef.ac.uk/images/grb151215.png