{
  "bibcode": "2017GCN.21541....1N",
  "body": "M. Nicholl (Harvard), P. S. Cowperthwaite (Harvard), S. Allam (Fermilab),\nJ. Annis (Fermilab), E. Berger (Harvard), D. J. Brout (UPenn), D. Brown\n(Syracuse), R. E. Butler (Fermilab), H.-Y. Chen (Harvard), R. Chornock\n(Ohio University), E. Cook (TAMU), , H. T. Diehl (Fermilab), A.\nDrlica-Wagner (Fermilab), M. R. Drout (Carnegie), R. J. Foley (UCSC), W.\nFong (Northwestern), D. Fox (Penn State), J. Frieman (Fermilab/UChicago),\nM.S.S. Gill (Stanford), R. Gruendl (NCSA), K. Herner (Fermilab), D. Holz\n(UChicago), R. Kessler (UChicago), R. Margutti (Northwestern), J. Marshall\n(TAMU), E. Neilsen (Fermilab), F. Paz-Chincon (NCSA), A. Rest (STScI), M.\nSako (UPenn), N. Smith (Arizona), M. Soares-Santos (BrandeisU), D. Tucker\n(Fermilab), V. A. Villar (Harvard), A. Walker (NOAO), P. K. G. Williams\n(Harvard), B. Yanny (Fermilab), P. Lopes (UFRJ), F. Durret (IAP), A.\nLouren��o (UFRJ)\n\nOn behalf of the DESGW+community team:\n\nWe report preliminary optical i- and z-band photometry from DECam imaging of\nthe possible optical counterpart to G298048 first identified in Coulter et\nal. (LVC GCN 21529),  and further reported on by Allam et al. (LVC GCN\n21530), Valenti et al. (LVC GCN 21531), Melandri et al. (LVC GCN 21532) and\nArcavi et al. (GCN 21538). Observations were obtained on 2017-08-18 at\n00:04 UTC.\n\nWe find preliminary PSF magnitudes of\n\ni = 17.5 +/- 0.1 mag\nz = 17.5 +/- 0.1 mag\n\nThis suggests an i-z color of 0 mag, which is consistent with the expected\ncolors of a Short GRB afterglow, but not for lanthanide dominated kilonova\nemission (e.g., Barnes & Kasen 2013, Barnes et al. 2016, Wollaeger et al.\n2017).\n\nThese magnitudes are determined from difference PSF photometry of DECam\nimages relative to Pan-STARRs 3pi catalogs.\n\nFurther analysis is ongoing.\n\n[GCN OPC NOTE(18aug17):  Per author's request, the trigger number\nin the Subject-line was changed from 298045 to 298048.]",
  "circularId": 21541,
  "createdOn": 1503031472000,
  "email": "pcowperthwaite@cfa.harvard.edu",
  "subject": "LIGO/VIRGO G298048: The Potential Optical Counterpart in NGC 4993 Has Afterglow-Like Colors",
  "submitter": "Philip Cowperthwaite at Harvard U  <pcowperthwaite@cfa.harvard.edu>",
  "eventId": "LIGO/VIRGO G298048"
}