{
  "version": 2,
  "body": "P.S. Cowperthwaite (Harvard), M. Nicholl (Harvard), E. Berger (Harvard)\n\nWe construct a preliminary UV/Optical/NIR SED for the potential optical\ncounterpart SSS17a first reported by Coulter et al. (GCN 21529). These data\nare compiled from the photometry reported in circulars submitted during the\nfirst night of follow-up. We correct these data for extinction due to\nreddening along the line of sight to the host galaxy NGC 4993.\n\nWe perform a preliminary fit with a blackbody function to this SED finding\nan effective temperature of T = 8000 K and an effective radius of R = 6e14\ncm.\n\nWe test the sensitivity of our fit to the UV flux, refitting with the\nSwift/UVOT data excluded. We find T = 10,200 K and R ~ 4e14 cm.\n\nIn both cases, the large expansion radius and short time since explosion (t\n~ 1 day) suggest an expansion velocity of >0.2c. This is too fast to be\nexplained by supernova ejecta, but is consistent with the expansion\nvelocities expected for relativistic BNS/NS-BH merger ejecta.\n\nThese values, and the inferred relativistic expansion, are consistent with\nthe results of Malesani et al. (GCN 21577).",
  "eventId": "LIGO/Virgo G298048",
  "createdOn": 1503097890000,
  "email": "pcowperthwaite@cfa.harvard.edu",
  "subject": "LIGO/VIRGO G298048: Expansion Velocity of SSS17a Consistent With Relativistic Merger Ejecta",
  "editedOn": 1777052862497,
  "submitter": "Philip Cowperthwaite at Harvard U  <pcowperthwaite@cfa.harvard.edu>",
  "editedBy": "Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov>",
  "bibcode": "2017GCN.21578....1C",
  "circularId": 21578
}