{
  "bibcode": "2019GCN.23986....1H",
  "body": "A. Hajela, R. Margutti, W. Fong , K. D. Alexander (Northwestern/CIERA), P.\nBlanchard (Harvard), R. Chornock (Ohio U.), D. Coppejans\n(Northwestern/CIERA), S. Gomez (Harvard), G. Hosseinzadeh  (Harvard), G.\nTerreran (Northwestern/CIERA), A. Villar (Harvard) report:\n\n���We report the results from the first 36ks of Chandra observations of\nGW170817 (another ~ 64ks will be acquired in the next few days). Chandra\nstarted to observe GW170817 on 21 March 2019 at 07:44 UT (obsID 21322,\nCo-PIs Margutti and Fong; program 20500299). X-ray emission from GW170817\nis detected at the level of ~3 sigma  (assuming pure Poissonian\nstatistics), with a 0.5-8 keV count-rate of  (1.5 +\\-0.7)e-4 c/s, and a\ntotal of ~5 net photons. Assuming a simple power-law spectrum with photon\nindex Gamma=1.6 and no intrinsic absorption, as found in previous Chandra\nobservations (e.g., Margutti et al., 2018; Alexander et al., 2018), the\ncount-rate above translates into an unabsorbed flux of  (2.3+\\- 1.1)e-15\nerg/s/cm2 (0.3-10 keV). The Galactic neutral hydrogen column density in the\ndirection of the transient is N_H = 7.8e+20cm-2 (Kalberla et al., 2005).\nThis flux measurement is consistent with the expectations from the fast\ndecay of the emission from the jet (e.g., Margutti et al., 2018; Alexander\net al., 2018; Wu et al., 2018). Further Chandra observations are ongoing.\n\nWe thank the entire Chandra team for making these observations possible.���",
  "circularId": 23986,
  "createdOn": 1553270568000,
  "email": "rafmargutti@gmail.com",
  "subject": "Chandra observations of GW170817 ~581 days since merger",
  "submitter": "Raffaella Margutti at Northwestern U  <rafmargutti@gmail.com>"
}