TITLE: GCN CIRCULAR NUMBER: 16360 SUBJECT: Fermi423717114: iPTF optical transient candidates DATE: 14/06/07 03:08:08 GMT FROM: Leo Singer at CIT/PTF L. P. Singer (Caltech), M. M. Kasliwal (Carnegie Observatories/Princeton), and S. B. Cenko (NASA/GSFC) report on behalf of the intermediate Palomar Transient Factory (iPTF) collaboration: Fermi GBM reported trigger 423717114 at 2014-06-06 03:11:51.86 UT. We have searched for optical counterparts using the Palomar 48-inch Oschin telescope (P48). Based on the final Fermi GBM localization, we observed 10 fields covering 73 deg2, with an estimated 56% chance of containing the true location of the event. Sifting through candidate variable sources using image subtraction and standard iPTF vetting procedures, we detected several optical transients. iPTF14bfu has no previous detections in iPTF from 2013-05-23 through 2013-10-13, and no obvious host associations. From 4.3 to 5.5 hours after the burst, it faded from r = 19.89 +/- 0.10 to 20.32 +/- 0.14 mag, fitting a power law of alpha = -1.6 +/- 0.7 relative to the time of the GBM trigger. It is at the coordinates: RA(J2000) = 21h 52m 29.97s (328.124877 deg) Dec(J2000) = +32d 00' 50.6" (+32.014053 deg) iPTF14bfw is coincident with the faint galaxy SDSS J220322.02+291451.1. It was at r = 19.96 +/- 0.06 and possibly fading, at the coordinates: RA(J2000) = 22h 03m 22.04s (330.841830 deg) Dec(J2000) = +29d 14' 51.8" (+29.247730 deg) iPTF14bgc, was at r = 18.44 +/- 0.02 and possibly fading. It is coincident with a r = 21.07 +/- 0.08 mag point source in our coadded reference image composed of exposures from 2013-07-31 through 2013-09-24. It is at the coordinates: RA(J2000) = 21h 45m 36.14s (326.400599 deg) Dec(J2000) = +32d 08' 57.9" (+32.149426 deg) iPTF14bga, was at r = 19.75 +/- 0.06 mag and possibly fading. It is coincident with a r = 20.42 +/- 0.17 mag point source in our reference image composed of exposures from 2011-07-29 through 2011-10-20. It is a the coordinates: RA(J2000) = 22h 12m 43.78s (333.182423 deg) Dec(J2000) = +33d 39' 43.7" (+33.662146 deg) Further observations are planned, and are encouraged to determine the nature of these candidates and determine if any of them are indeed associated with the Fermi trigger. The diagram http://www.its.caltech.edu/~lsinger/iptf/Fermi423717114.pdf shows the locations of our candidates and the ten P48 fields in relation to the Fermi GBM 1- and 2-sigma statistical+systematic contours. We thank the Fermi-GBM team for sharing their detailed localizations with us.