{
  "bibcode": "2019GCN.24592....1P",
  "body": "Dheeraj Pasham (MIT), Keith Gendreau (NASA/GSFC), Zaven Arzoumanian\n(NASA/GSFC), Stephen Eikenberry (UFL), Wynn C.G. Ho (Haverford) report on\nbehalf of the NICER team:\n\nThe transient ZTF19aassfws (Perley et al., GCN#24331) fell in the\nLIGO/Virgo error box of the trigger S190426c (LVC et al., GCN#24237), and\nCenko et al. (GCN#24430) found that its distance is consistent with that\ninferred from the gravitational wave signal. NICER observed this target for\n7 ks, approximately half of which was in especially low background/high\nsensitivity conditions.\n\nWe do not detect any X-ray emission above the background from this region.\nAssuming an X-ray spectrum with a power-law index of 1.7 (similar to\nGW170817) at a redshift of 0.093 with an absorbing column of 8e20 cm**-2\n(Milky Way column), we estimate an upper limit on the unabsorbed 0.35-11.5\nkeV X-ray flux of 1.3e-13 erg/s/cm**2.\n\nNICER can carry out prompt follow-up observations of transients and is\nplanning to systematically follow up alerts from LIGO/Virgo and other X-ray\nbright extra-galactic transients in the future.\n\nNICER is a 0.2-12 keV X-ray telescope operating on the International Space\nStation. The NICER mission and portions of the NICER science team\nactivities are funded by NASA.",
  "circularId": 24592,
  "createdOn": 1558233436000,
  "email": "dheeraj@space.mit.edu",
  "subject": "LIGO/Virgo S190426c: NICER X-ray Follow-Up of ZTF19aassfws",
  "submitter": "Dheeraj R. Pasham at Mass. Inst. of Technology  <dheeraj@space.mit.edu>",
  "eventId": "LIGO/Virgo S190426c"
}