{
  "bibcode": "2021GCN.29953....1H",
  "body": "Anna Ho (UC Berkeley), Yuhan Yao (Caltech), and Daniel Perley (LJMU)\n\nWe observed the cosmological fast transient ZTF21aayokph/AT2021lfa (Yao,\nPerley, and Ho, GCN Circ. 29938) with Swift/XRT beginning at 2021-05-05\n05:32 UT, or 1.0d after the first ZTF detection. In a 5ks exposure, we\ndetect X-ray emission with a count rate of 0.0084 +/- 0.0015 ct/s. Using\nWebPIMMS [1] we estimate [2] that this corresponds to an unabsorbed 0.3-10\nkeV flux density of 2.9E-13 ergs/cm2/s. At z=1.063 (Yao, Ho, and Perley,\nGCN Circ. 29945) this is a luminosity of 1.9E45 erg/s, typical of an X-ray\nafterglow of a long-duration GRB at this epoch [3].\n\nWe thank the Swift staff for rapidly approving and scheduling our\nobservations.\n\n[1] https://heasarc.gsfc.nasa.gov/cgi-bin/Tools/w3pimms/w3pimms.pl\n[2] Using a hydrogen column density of 2.16E20/cm2 (Willingale, R., et al.\n2013, MNRAS, 431, 394) and a power-law index of 2\n[3] Evans, P.~A., et al. 2007, AAP, 469, 379",
  "circularId": 29953,
  "createdOn": 1620333119000,
  "email": "annayqho@berkeley.edu",
  "subject": "ZTF21aayokph (AT2021lfa): X-ray Detection with Swift/XRT",
  "submitter": "Anna Ho at UC Berkeley  <annayqho@berkeley.edu>",
  "eventId": "ZTF21aayokph"
}