{
  "bibcode": "2019GCN.26062....1P",
  "body": "D. A. Perley (LJMU), D. B. Malesani (DTU Space), A. J. Levan (Radboud \nUniv.), J. P. U. Fynbo (DAWN/NBI), and A. A. Djupvik (NOT) report on \nbehalf of a larger collaboration:\n\nWe obtained additional observations of the optical counterpart (Reva et \nal., GCN 26036; LaPorte & Simpson, GCN 26053; Zhu et al., GCN 26059) of \nGRB 191019A (Simpson et al., GCN 26031), using the Nordic Optical \nTelescope (NOT) equipped with the ALFOSC camera.  A total of 25 minutes \nexposure was secured with mid time Oct 22.875 UT (77.8 hr after the GRB).\n\nThe archival object consistent with the XRT error circle is well \ndetected, with a magnitude of i = 18.71 +/- 0.02 AB, consistent with the \nPan-STARRS tabulated value of i = 18.71 +/- 0.01 and slightly fainter \nthan our earlier observation (Perley et al., GCN  26039), for which the \nmid time was 4.60 hr after the GRB.\n\nDigital image subtraction was carried out with ISIS (Alard 2000, A&AS, \n144, 363) between the two epochs. A clear point-like residual is \ndetected, for which we measure a magnitude i = 21.78 +/- 0.05 AB \n(assuming no residual flux in our second epoch). Its position calibrated \nagainst the Gaia catalog is:\n\nRA(J2000) = 22:40:05.89\nDec(J2000) = -17:19:42.6\n\n(+/- 0.3\")\n\nAn image showing the subtraction result is available here: \nhttp://outer.space.dtu.dk/~dmales/GRB/191019A/subtraction.jpg\n\nThe transient location is 0.07\" east of the galaxy nucleus, \nstrengthening the case for a physical association between the two \nobjects.  The offset is within the margin of error, although the NOT \nspectroscopy (Fynbo et al., GCN 26041) does not suggest that the source \nis an AGN.\n\nOur observations thus confirm the presence of a transient optical source \nat a position consistent with the X-ray afterglow, located to within the \nerrors on top of the nucleus of the candidate host. The lack of any \nnon-obscured star formation makes this system unique among long-duration \nGRBs.\n\nWe encourage observations of this puzzling source at all wavelengths.\n\n\n\n\n\n\n\n\n\nDisclaimerNone",
  "circularId": 26062,
  "createdOn": 1571867737000,
  "email": "d.a.perley@ljmu.ac.uk",
  "subject": "GRB 191019A: NOT optical afterglow and host association confirmation",
  "submitter": "Daniel Perley at Liverpool JMU  <d.a.perley@ljmu.ac.uk>",
  "eventId": "GRB 191019A"
}