{
  "bibcode": "2013GCN.15574....1S",
  "body": "L. P. Singer (Caltech), M. M. Kasliwal (Carnegie Observatories),\nS. B. Cenko (NASA/GSFC), Yi Cao (Caltech), Daniel Perley (Caltech),\nand Annalisa De Cia (Weizmann) report on behalf of the intermediate\nPalomar Transient Factory (iPTF) collaboration:\n\nWe report our continued observations of the optical transient\niPTF13ecv (Singer & Kasliwal, GCN 15524; Xu et al., GCN 15531; Quadri\net al., GCN 15543; Quadri et al., GCN 15558), which was spatially\ncoincident with the Fermi GBM localization of GRB 131127B (von\nKienlin, GCN 15528) but was well outside the IPN error box\n(Golenetskii et al., GCN 15529).\n\nNo X-ray source coincident with iPTF13ecv was detected in a 5 ks Swift\nXRT observation starting at 2013-11-28 10:10 (0.83 days after the\nFermi-GBM trigger). We calculate a 3 sigma upper limit on the count\nrate of < 2.2e-3 cps at this time.\n\nWe obtained further optical photometry with the robotic Palomar\n60-inch telescope (P60), yielding r=19.0 +/- 0.1 mag at 2013-11-30\n03:36.\n\nOn 2013-11-29, we obtained a spectrum with the DEIMOS instrument on\nthe Keck II telescope. The spectrum was blue and featureless from\nabout 5000 to 8500 angstroms.\n\nOn 2013-12-02, we obtained a second spectrum with the LRIS instrument\non Keck I. This spectrum had a blue continuum with prominent Balmer\nabsorption lines at a redshift of z=0.\n\nConsidering the position well outside the IPN localization, the\ncontinued optical detection of iPTF13ecv, its blue optical SED, and\nthe Balmer absorption lines, we conclude that iPTF13ecv is unrelated\nto the GRB trigger and is likely a cataclysmic variable in outburst.\n\nWe also note that the other two iPTF candidates reported in GCN\n15524, iPTF13ect and iPTF13ecu, are probably due to AGN activity. In\nthe 6dFGS survey (Jones et al., MNRAS, 355, 747), iPTF13ect displays\na Seyfert I-type spectrum (broad H-alpha and strong [N II] emission\nlines) and iPTF13ecu a Seyfert II spectrum (no broad H-alpha\nemission, but strong [N II] emission lines).",
  "circularId": 15574,
  "createdOn": 1386132150000,
  "email": "lsinger@caltech.edu",
  "subject": "GRB 131127B: rejection of optical counterpart candidates",
  "submitter": "Leo Singer at CIT/PTF  <lsinger@caltech.edu>",
  "eventId": "GRB 131127B"
}