TITLE:   GCN CIRCULAR
NUMBER:  17612
SUBJECT: GRB 150323A: P60 Optical Afterglow Candidate
DATE:    15/03/23 03:51:38 GMT
FROM:    S. Bradley Cenko at NASA/GSFC  <brad.cenko@nasa.gov>

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

We observed the location of the Swift GRB150323A (Amaral-Rogers et al., GCN 17611) with the robotic Palomar 60 inch telescope.  Observations began at 2:57 UT (~ 8 minutes after the Swift trigger) and were obtained in the Sloan r, i, and z filters.  In a stacked r-band image with a mid-point of 3:07 UT, we detect a source at the edge of the XRT error circle, with coordinates:

  RA: 08:32:42.83    Dec: +45:27:53.5   (J2000.0)

At this time, we measure an r-band magnitude of ~ 20.6 (photometric calibration performed with respect to nearby point sources from SDSS). Given the lack of a quiescent counterpart in SDSS at this location, we consider this likely to be the afterglow of GRB150323A.

Observations are ongoing.