{
  "bibcode": "2014GCN.17079....1S",
  "body": "L. P. Singer (Caltech), M. M. Kasliwal (Carnegie Observatories/Princeton),\nV. B. Bhalerao (IUCAA), and S. B. Cenko (NASA/GSFC) report on behalf of\nthe intermediate Palomar Transient Factory (iPTF) collaboration:\n\nWe searched for optical counterparts of GRB 141118A (GCN 17073, Hurley\net al.; GCN 17074, Golenetskii et al.) using the Palomar 48-inch Oschin\ntelescope (P48). At about 18 hours after the burst, we began imaging 20\nfields spanning an area of 145 deg2, covering most of the 1-sigma\nstatistical+systematic region of the final Fermi GBM localization (Fermi\ntrigger 438020153 / 141118678). Based on the GBM localization, we estimate\na 77% chance that these fields contain the true location of the source.\nCoincidentally, we estimate the same containment probability based on the\nIPN error box.\n\nSifting through candidate variable sources using image subtraction and\nstandard iPTF vetting procedures, we detect the optical transient\niPTF14hvs, at the coordinates:\n  RA(J2000)  =  10h 26m 05.29s (156.522055 deg)\n  Dec(J2000) = +18d 34' 08.6\"  (+18.569044 deg)\nThis position is just inside the error box. It is also in the outskirts of\nthe galaxy SDSS J102605.09+183411.6, which has a photoZ of ~0.1. In host-\nsubtracted P48 photometry, we find marginal evidence that the source faded:\n  +18.41 hours:  R = 19.92 +/- 0.14\n  +19.06 hours:  R = 20.03 +/- 0.08\nTimes are relative to the GBM trigger. Magnitudes are in the Mould R filter\nand in the AB system, calibrated with respect to point sources in SDSS as\ndescribed in Ofek et al. (2012, http://dx.doi.org/10.1086/664065).\n\nWe obtained a series of spectra of iPTF14hvs with the Gemini Multi-Object\nSpectrograph mounted on the 8 m Gemini North telescope beginning at 15:21\nUT on 2014 Nov 11. The spectra cover the wavelength range of 3900-9200 A.\nCross-correlation with a library of supernova spectra using the\n``Supernova Identification'' code (SNID; Blondin and Tonry 2007, ApJ 666,\n1024) indicates the source is a type Ia supernova several weeks past\nmaximum light at z ~ 0.11. Spatially offset from the transient location we\nidentify narrow emission lines of H-alpha, [N II], and [S II] at a common\nredshift of z = 0.108.\n\nWe conclude that iPTF14hvs is not related to the GRB.\n\nThe diagram http://www.its.caltech.edu/~lsinger/iptf/Fermi438020153.pdf\nshows our P48 fields and the location of the optical transient in relation\nto the Fermi GBM 1- and 2-sigma statistical+systematic contours and the\nIPN annulus.\n\nWe thank the IPN team for promptly sharing their analysis.",
  "circularId": 17079,
  "createdOn": 1416555466000,
  "email": "lsinger@caltech.edu",
  "subject": "GRB 141118A: iPTF Optical Observations",
  "submitter": "Leo Singer at CIT/PTF  <lsinger@caltech.edu>",
  "eventId": "GRB 141118A"
}