{
  "bibcode": "2020GCN.28169....1M",
  "body": "Daniele B. Malesani (DTU Space), Antonio de Ugarte Postigo (HETH, \nIAA-CSIC; DARK/NBI), Luca Izzo (DARK/NBI), Jens Hjorth (DARK/NBI), D. \nAlexander Kann (HETH, IAA-CSIC), Christina C. Thoene (HETH, IAA-CSIC), \nMartin A. Guerrero (IAA-CSIC), report on behalf of a larger collaboration:\n\nWe observed the field of GRB 200729A (Evans et al., GCN 28165) with the \nNordic Optical Telescope equipped with the ALFOSC imager. Observations \nwere carried out in the r and z filters, and started on 2020 Jul 29.911 \nUT (2.2 hr after the trigger), as soon as visibility allowed.\n\nWithin the XRT position of the candidate afterglow (Osborne et al., GCN \n28168), we detect no new sources compared to archival Pan-STARRS images. \nThe 3-sigma limiting magnitudes are:\n\nr > 22.5 AB\nz > 22.0 AB\n\nAs noted by Evans et al. (GCN 28165), the location of the X-ray source \nlies on top of the nearby galaxy NGC 4242, whose distance is ~5.5 Mpc \n(from Simbad, which however presents values up to 10 Mpc). We note that, \nif the GRB is associated with NGC 4242, our limit would correspond to an \nabsolute magnitude M_r > -6.2, which, in lack of significant extinction, \nprovides a deep limit to the GRB optical luminosity. For example, the \nearliest detection of SN 2008D (3.5 hr after the outburst; Soderberg et \nal. 2008, Nat, 453, 469) had an absolute U-band magnitude M(U) = -12.3 \n(even before correcting for the significant extinction).\n\nAt 5.5 Mpc, the gamma-ray fluence of 8*10^-7 erg cm^-2 (taken from \nhttps://gcn.gsfc.nasa.gov/notices_s/984929/BA/) would correspond to \n3*10^45 erg - fainter than the low-luminosity events GRB 980425, GRB \n170817A, and the X-ray output of SN 2008D.\n\nWhile the visibility of this target from La Palma is now over, we \nencourage further observations from other locations.",
  "circularId": 28169,
  "createdOn": 1596066629000,
  "email": "malesani@space.dtu.dk",
  "subject": "GRB 200729A: NOT optical upper limits",
  "submitter": "Daniele B Malesani at DTU Space  <malesani@space.dtu.dk>",
  "eventId": "GRB 200729A"
}