TITLE:   GCN CIRCULAR
NUMBER:  18537
SUBJECT: GRB 151027A: Continued P60 Monitoring
DATE:    15/10/30 14:37:08 GMT
FROM:    S. Bradley Cenko at NASA/GSFC  <brad.cenko@nasa.gov>

S. B. Cenko (NASA-GSFC) and D. A. Perley (DARK/NBI) report on behalf of a larger collaboration:

We have continued to image the optical afterglow of GRB151027A (Maselli et al., GCN 18478) with the robotic Palomar 60-inch telescope (see Perley et al., GCN 18481). We report the following r’-band photometry, calibrated with respect to nearby point sources from the APASS survey:

t_mid                                time since burst (d)          Magnitude
—————————————————————————————————
2015-10-29T02:14:14      1.93                                   19.63 +/- 0.04
2015-10-30T02:02:28      2.92                                   20.48 +/- 0.08

This implies a relatively steep power-law decay index of ~ 1.9 at these times.

Continued observations are planned.