{
  "bibcode": "2019GCN.26175....1R",
  "body": "A. Rouco Escorial, W. Fong, (Northwestern), E. Berger (Harvard), and R. Margutti (Northwestern) report:\n\n\"We initiated observations of the location of the short-duration GRB191031D (Fermi-GBM et al., GCN 26111; D'Elia et al., GCN 26112; Mailyan et al., GCN 26118) with the Chandra X-ray Observatory on 2019 Nov 3.694 UT (mid-time of 16:39:42 UT), 2.8 days post-burst under Program 20500021 (ObsID 21302; PI: Berger). The effective exposure time is 19.8 ksec.\n\nWe do not detect an X-ray source within the enhanced XRT position (Osborne et al., GCN 26117), and calculate a 3-sigma limit of <4.5e-4 cps in the 0.5-10 keV energy range using the method described by Gehrels (1986). Applying the best-fit XRT spectral parameters, we calculate an unabsorbed flux limit of <6.0e-15 erg/s/cm^2 in the 0.3-10 keV energy range. \n\nRelative to the XRT light curve starting from t~900 sec post-burst, this constrains the late-time X-ray power-law decline to be alpha<-0.75 (where F~t^alpha).\n\nWe thank the Chandra staff for the rapid scheduling and execution of these observations.\"",
  "circularId": 26175,
  "createdOn": 1572965439000,
  "email": "wfong@northwestern.edu",
  "subject": "GRB 191031D: Chandra upper limit",
  "submitter": "Wen-fai Fong at Northwestern U  <wfong@northwestern.edu>",
  "eventId": "GRB 191031D"
}