{
  "bibcode": "2014GCN.16226....1S",
  "body": "L. P. Singer (Caltech), S. B. Cenko (NASA/GSFC), M. M. Kasliwal\n(Carnegie Observatories/Princeton), Christoffer Fremling (Stockholm\nUniversity), and Yifat Dzigan (Weizmann) report on behalf of the\nintermediate Palomar Transient Factory (iPTF) collaboration:\n\nWe have searched for an optical counterpart of GRB 140508A (Yu and\nGoldstein, GCN 16224), Fermi/GBM trigger 421211037 (2014-05-08\n03:03:54.60), using the Palomar 48-inch Oschin telescope (P48). Based\non the final Fermi GBM localization, we observed 10 fields covering\n73 deg2, with an estimated 67% chance of containing the true location\nof the event. Due to weather at Palomar early in the night,\nobservations started at 09:48 UTC, 6.7 hours after the trigger.\n\nAlso detected by Konus-Wind, INTEGRAL, Swift BAT (outside FoV), and\nMESSENGER, the IPN error box (Hurley et al., GCN 16225) was mostly\ncontained within two CCDs in one of our fields.\n\nSifting through candidate variable sources using image subtraction\nand standard iPTF vetting procedures, we detected several optical\ntransients. Only is located within the IPN error box:\n\niPTF14aue, at the coordinates:\n  RA(J2000)  =  17h 01m 51.95s (255.466450 deg)\n  Dec(J2000) = +46d 46' 49.5\"  (+46.780417 deg)\n\nThe source was detected at r = 17.89 +/- 0.01 mag and appeared to\nfade. A power-law fit to the first two observations, relative to the\ntime of the GBM trigger, gives a decay index of alpha = 1.12 +/- 0.1.\nThere is no source coincident with this location in our reference\nimages or in SDSS DR10.\n\nThis position is also consistent with the IPN triangulation\n(Hurley et al., GCN 16225), and is 7' from the center of the error\nbox.\n\nGiven the spatial coincidence with the IPN localization, the lack of\narchival detections, and the source fading, iPTF14aue is likely\nassociated with the GRB. We are submitting a Swift XRT target of\nopportunity. Further observations are encouraged to confirm the\nassociation and the nature of the candidate.\n\nThe diagram\nhttp://www.its.caltech.edu/~lsinger/iptf/Fermi421211037.pdf shows the\nten P48 fields in relation to the Fermi GBM 1- and 2-sigma\nstatistical+systematic contours, and the IPN error box.\n\nWe thank the Fermi-GBM and IPN teams for sharing their localizations\nwith us.",
  "circularId": 16226,
  "createdOn": 1399577409000,
  "email": "lsinger@caltech.edu",
  "subject": "GRB 140508A: iPTF optical transient candidate",
  "submitter": "Leo Singer at CIT/PTF  <lsinger@caltech.edu>",
  "eventId": "GRB 140508A"
}