{
  "bibcode": "2017GCN.20802....1A",
  "body": "S. M. Adams (Caltech), C. Cannella (Caltech), A. A. Miller\n(Northwestern/Adler), S. Papadogiannakis (OKC), R. Lunnan (Caltech), N.\nBlagorodnova (Caltech), L. P. Singer (NASA/GSFC), S. B. Cenko (NASA/GSFC),\nR. Walters (Caltech), T. Barlow (Caltech), J. Rana (IUCAA), V. Bhalerao\n(IIT-B),  Y. Cao (UW), R. Laher (IPAC), F. Masci (IPAC) and M.M. Kasliwal\n(Caltech)\n\nreport on behalf of the iPTF (intermediate Palomar Transient Factory) and\nGROWTH (Global Relay of Observatories Watching Transients Happen)\ncollaborations:\n\nWe have continued tiled observations of LIGO/Virgo G275404 (LVC, GCN\n20738) and LIGO/Virgo G275697 (LVC, GCN 20763) using the Palomar 48-inch\nOschin telescope (P48). Including our first night of observations on\n2017-03-01 UTC (GCN 20791) and a second night on 2017-03-02, we have\nobserved a total of 240 fields spanning 1747 square degrees. We estimate a\n20% chance that these fields contain the true location of G275404 and a\n25% chance that they containing the true location of G275697.\n\nDuring preliminary sifting through candidate variable sources using image\nsubtraction by our IPAC (Masci et al. 2016) and NERSC (Cao et al. 2016)\npipelines, a total of 115 candidates were saved in the fields imaged.\nApplying standard iPTF vetting procedures and removing transients with a\nhistory of previous variability, we flagged 16 optical transient candidates\nin the 90% localization contour of G275697, listed below, for further\nfollow-up.\n\nWe encourage spectroscopic classification of these candidates. In\nparticular, we highlight 17bub and 17buo as fast-evolving by more than 0.3\nmag in the same night.\n\nWe are grateful to the Palomar crew (John Henning, Jeff Zolkower, Carolyn\nHeffner, Jamey Eriksen, Nick Ganciu) for their hard work in reviving a\nfaulty declination encoder essential to collecting this dataset during the\nlast two days of iPTF survey operations.\n\niPTF17bti   0.800077        67.402379       02:38  18.67\npstar=0.957; nuclear/stellar?\niPTF17btj   27.422253       68.506993       02:53  18.34\npstar=0.91; nuclear/stellar?\niPTF17bto   53.02396        70.025567       03:38  17.87\nnuclear/stellar?\niPTF17btp   68.216762       72.512217       03:46  19.23\npstar=0.969; nuclear/stellar?\niPTF17bub   85.525185       70.159774       04:32  18.72\npstar=0.946; nuclear/stellar?; fading (0.84 mag intra-night)\niPTF17bue   54.623802       71.407755       03:38  18.04\noff-center from host galaxy\niPTF17bun   57.584087       72.275187       03:35  18.63\npstar=0.909; nuclear/stellar?\niPTF17buo   49.553246       73.391128       03:35  18.39\npstar=0.166; nuclear/stellar?; fading (0.69 mag intra-night)\niPTF17buq   41.070946       69.589982       03:28  18.9\npstar=0.996; nuclear/stellar?\niPTF17bvd   83.199221       71.328788       04:32  20.1            hostless\nin iPTF reference; possible marginal counterpart seen in PS1.\niPTF17bvw   85.92019        70.584375       04:32  19.74           hostless\nin iPTF and PS1\niPTF17bvx   72.69051        69.373832       04:17  19.36\npstar=0.918; nuclear/stellar?\niPTF17bvz   66.258018       69.031885       04:17  19.81\npstar=0.889; nuclear/stellar?\niPTF17bwi   82.2476         71.146032       04:24  20.16\npstar=0.958; nuclear/stellar?\niPTF17bwj   141.533287      7.757573        07:09  19.39   0.441   specz;\nnuclear; SDSS QSO\niPTF17bxa   76.262387       69.156295       04:26  19.66           nuclear;\npstar=0.01\n\nTwo known transients detected in early January also fall in the\nlocalization region and were recovered with iPTF: PS17m (=iPTF17D) and\nPS17n/Gaia17aan (=iPTF17G).\n\nPositions are stated in the ICRS. Discovery times are noted in UTC hh:mm on\n2017-03-02. Magnitudes are based on image subtraction and in the Mould R\nfilter, calibrated with respect to point sources in SDSS as described in\nOfek et al. 2012.\n\nWe caution that many candidates are outside the SDSS footprint and lack a\nsecure star/galaxy classification for the underlying source. We flag these\nas \"nuclear/stellar?\". Where available, we provide machine-learning\nprobability scores on whether the underlying source is a galaxy/star (0/1)\n(Miller et al. 2016).\n\nWe encourage spectroscopic classification of these candidates. In\nparticular, we highlight 17bub and 17buo as fast-evolving by more than 0.3\nmag in the same night.\n\nWe are grateful to the Palomar crew (John Henning, Jeff Zolkower, Carolyn\nHeffner, Jamey Eriksen, Nick Ganciu) for their hard work in reviving a\nfaulty declination encoder essential to collecting this dataset during the\nlast two days of iPTF survey operations.",
  "circularId": 20802,
  "createdOn": 1488515373000,
  "email": "mansi@astro.caltech.edu",
  "subject": "LIGO/Virgo G275697: Additional iPTF Optical Transient Candidates",
  "submitter": "Mansi M. Kasliwal at Caltech  <mansi@astro.caltech.edu>",
  "eventId": "LIGO/Virgo G275697"
}