{
  "bibcode": "2014GCN.16442....1B",
  "body": "V. B. Bhalerao (IUCAA), L. P. Singer (Caltech), M. M. Kasliwal\n(Carnegie Observatories/Princeton), S. B. Cenko (NASA/GSFC), A. Horesh\n(Weizmann Institute) and D. A. Perley (Caltech) report on behalf of\nthe intermediate Palomar Transient Factory (iPTF) collaboration: \n\nFermi GBM reported trigger 425193729 at 2014-06-23 05:22:06.600 UT.\nStarting 2014-06-23 05:33:07.776 UT (JD 2456831.73134, 11 min after\ntrigger), we began our search for optical counterparts using the\nPalomar 48-inch Oschin telescope (P48).  Based on the automated Fermi\nground localization, we selected 10 fields covering an area of 74\ndeg^2.\n\nThe final Fermi localization, available 2.6 hours after the trigger,\ndiffered in position by 13.4 deg. Based on the final localization and\nan empirical description of the systematic errors of the GBM\nlocalization (Paciesas et al. 2012,\nhttp://dx.doi.org/10.1088/0067-0049/199/1/18), we estimate a 4% chance\nthat these fields contain the true location of the source.\n\nSifting through candidate transient sources using image subtraction\nand standard intermediate Palomar Transient Factory vetting\nprocedures, we detected several optical transients. The fastest fading\ntransient was iPTF14cyb, at the coordinates:\n  RA(J2000)  =  15h 01m 53.42s  (225.472574 deg)\n  Dec(J2000) = +81d 11' 29.1\"   (+81.191410 deg)\n\nWe note that the position of 1PTF 14cyb is consistent with both the\niniital ground and final localizations.\n\nMeasured R magnitudes of iPTF14cyb are\n   JD          R\n2456831.73527 18.0\n2456831.75906 19.3\n2456831.78167 19.7\n\nThese are consistent with a power-law decay with index -0.93 +- 0.17.\n\nWe observed iPTF14cyb with the Gemini Multi-Object Spectrograph\nmounted on the 8m Gemini North telescope beginning at 08:10 UT on 2014\nJune 23 (~ 2.8 hr after the GBM trigger). Two 900 s spectra were\nobtained, covering the wavelength range from 4000-9300 A.\nSuper-imposed on a relatively flat continuum, we detect a number of\nstrong absorption features, including Mg II, Fe II, Al II, Si II, Al\nIII, C I, and C IV, at a common redshift of z = 1.92.  The lack of\nLy-alpha absorption in the spectrum suggests that this is the redshift\nof the Fermi GBM GRB. In addition, we detect strong absorption\nfeatures (Mg II, Fe II) from an intervening system at a redshift of z\n= 1.06.\n\nThe diagram\nhttp://www.its.caltech.edu/~lsinger/iptf/Fermi425193729.pdf shows the\nlocations of the afterglow and the 10 P48 fields in relation to the\nFermi GBM 1- and 2-sigma statistical+systematic contours.\n\nWe have triggered follow-up observations with Swift, EVLA and CARMA.\nWe encourage follow-up observations to confirm the nature of the\nsource. \n\nWe thank GoGo Inflight Wifi for internet at 10,000 feet.",
  "circularId": 16442,
  "createdOn": 1403531926000,
  "email": "varunb@iucaa.ernet.in",
  "subject": "Fermi 425193729 / iPTF14cyb: Discovery of optical afterglow",
  "submitter": "Varun Bhalerao at IUCAA  <varunb@iucaa.ernet.in>"
}