{
  "bibcode": "2014GCN.15971....1S",
  "body": "L. P. Singer (Caltech), S. B. Cenko (NASA/GSFC), and M. M. Kasliwal\n(Carnegie Observatories/Princeton) report on behalf of the intermediate\nPalomar Transient Factory (iPTF) collaboration:\n\nWe have searched for optical counterparts of Fermi GBM trigger 416242156\n(2014-03-11 14:49:13.10) using the Palomar 48-inch Oschin telescope (P48).\nWe observed 10 fields, covering 73.0 deg2 and most of the Fermi GBM\n1-sigma contour. We estimate a 54% chance that our fields contain the\nlocation of the source. Sifting through candidate variable sources using\nimage subtraction and standard iPTF vetting procedures including\nphotometry with the robotic Palomar 60\" telescope (P60), we detect the\ncandidate optical transient iPTF14aak, the coordinates:\n\n  RA(J2000)  =  11h 33m 14.47s (173.310295 deg)\n  Dec(J2000) = +62d 05' 10.7\"  (+62.086313 deg)\n\nIn our P48 image taken dt=0.51 days after the Fermi trigger, we measure\nr = 19.7 +/- 0.1 mag. In our P60 image taken dt=0.82 days after the\ntrigger, we find a limit of r > 20.10 mag.\n\nGiven a bright star about 1.3' to the west, it is possible that the P48\ndetection is a ghost. If not, then the P60 non-detection is evidence of\nfading with a power law of at least alpha~0.8.\n\nWe have submitted a Swift target of opportunity to search for an X-ray\ncounterpart of iPTF14aak. Further observations are encouraged to confirm\nthe nature of the source, and determine if it is associated with the Fermi\ntrigger.\n\nThe diagram http://www.its.caltech.edu/~lsinger/iptf/Fermi416242156.pdf\nshows the ten P48 fields and the position of iPTF14aak in relation to the\nFermi GBM 1- and 2-sigma statistical+systematic contours.",
  "circularId": 15971,
  "createdOn": 1394650202000,
  "email": "lsinger@caltech.edu",
  "subject": "Fermi416242156: possible iPTF counterpart",
  "submitter": "Leo Singer at CIT/PTF  <lsinger@caltech.edu>"
}