{
  "bibcode": "2016GCN.18995....1S",
  "body": "L. P. Singer (NASA/GSFC), S. B. Cenko (NASA/GSFC), M. M. Kasliwal\n(Caltech), and V. Bhalerao (IUCAA) report on behalf of a larger\ncollaboration:\n\nFermi GBM detected GRB 160206B (trigger 476446756 / bn160206430) at\n2016-02-06 10:19:12.43. At 10:29:40, about 10 minutes after the burst, we\nbegan searching for optical counterparts using the Palomar 48-inch Oschin\ntelescope (P48).\n\nWe imaged 114 fields covering an area of 379 deg^2 and covering most of\nthe 2-sigma statistical+systematic region of the final Fermi GBM\nlocalization. We estimate a 84% prior probability that these fields\ncontain the true location of the source. Sifting through candidate\nvariable sources using image subtraction and standard iPTF vetting\nprocedures, we detected the following optical transient candidates:\n\n   name       RA        Dec      mag   t    Notes\n----------------------------------------------------------------------------\n                   Hosts with spectroscopic redshifts\n----------------------------------------------------------------------------\niPTF16ca 181.162415 +45.059301 19.97 +2.39 z=0.190, host is an X-ray source\niPTF16ce 188.768138 +47.301857 20.27 +2.81 z=0.131\niPTF16ch 189.333005 +51.432720 20.70 +1.82 z=0.120\niPTF16cc 187.973175 +45.076476 19.12 +2.73 z=0.062, poor subtraction in interacting host galaxy\niPTF16cl 170.605169 +59.384422 20.12 +1.79 z=0.051\niPTF16cd 187.947490 +47.927964 19.48 +1.39 z=0.030\n----------------------------------------------------------------------------\n                    Hosts with photometric redshifts\n----------------------------------------------------------------------------\niPTF16cg 175.872772 +50.316844 19.65 +2.30 z=0.31\niPTF16ci 180.780807 +53.977868 19.49 +1.73 z=0.27\niPTF16ck 193.756732 +57.354180 20.42 +2.93 z=0.19\niPTF16cf 197.002541 +48.632699 20.05 +2.08 z=0.13\niPTF16bx 116.788070 +22.170396 19.20 -1.32 z=0.09\n\nTimes are in hours since the GBM trigger. Magnitudes are in the Mould R\nfilter and in the AB system, calibrated with respect to point sources in\nSDSS as described in Ofek et al. (2012, http://dx.doi.org/10.1086/664065).\n\nFurther observations of the above candidates are encouraged to determine\ntheir nature and if one of them is the optical afterglow of the GRB. We\nhave scheduled additional imaging of the P48 fields tonight.\n\nThe diagram http://asd.gsfc.nasa.gov/Brad.Cenko/Fermi476446756.pdf\nshows the locations of our candidates and the P48 fields in relation to\nthe Fermi GBM 1-, 2-, and 3-sigma statistical+systematic contours.",
  "circularId": 18995,
  "createdOn": 1454781732000,
  "email": "leo.p.singer@nasa.gov",
  "subject": "GRB 160206B: iPTF P48 Observations and Optical Transient Candidates",
  "submitter": "Leo Singer at GSFC/iPTF  <leo.p.singer@nasa.gov>",
  "eventId": "GRB 160206B"
}