TITLE: GCN CIRCULAR NUMBER: 15327 SUBJECT: Fermi403206457: continued P60 observations and fading behavior DATE: 13/10/13 07:26:44 GMT FROM: Daniel Perley at Caltech D. A. Perley (Caltech), S. B. Cenko (GSFC), and M. M. Kasliwal (Carnegie Observatories/Princeton) report: We imaged PTF13dsw, the possible optical counterpart to Fermi trigger 403206457 (Kasliwal et al., GCN 15324) with the Palomar 60-inch telescope starting at 05:16:19 UT in i, r, and g filters. Five exposures of 180 seconds each were acquired per filter. Calibrating to USNO B1.0 stars in the field, photometry of the candidate gives an approximate magnitude of R = 21.2 (+/- 0.2) in a stack of 15 minutes of r-band imaging at midpoint UT 05:40. As also noted by Malesani et al. (GCN 15325) the continued, significant fading relative to the previous night is consistent with that of a GRB afterglow and strengthens the association of this source with the Fermi trigger.