{
  "bibcode": "2023GCN.33472....1S",
  "body": "At the time of the very bright GRB 230307A (GCN #33405, GCN #33406, GCN \n#33407, GCN #33410, GCN #33411, GCN #33412, GCN #33413, GCN #33414, GCN \n#33415, GCN #33416, GCN #33418, GCN #33419, GCN #33424, GCN #33425, GCN \n#33427, GCN #33428, GCN #33429, GCN #33430, GCN #33431, GCN #33434, GCN \n#33437, GCN #33438, GCN #33439, GCN #33442, GCN #33443, GCN #33444, GCN \n#33447, GCN #33448, GCN #33449, GCN #33453, GCN #33459, GCN #33461, GCN \n#33465, GCN #33466), INTEGRAL was pointing 74 deg from the GRB \ndirection. Such an exceptionally high flux lead to a detection in \nvarious ratemeters of INTEGRAL often causing saturation. From moderately \nsaturated SPI-ACS observation, we can estimate a likely close lower \nlimit on the total flux in 75 - 2000 keV energy range at the level of \n0.0015 erg cm-2 s-1 in the time range T0 to T0+130.0s where T0 = \n2023-03-07T15:44:07.\n\nWe note that despite the GRB brightness, both SPI-ACS and PICsIT \nobservations do not reveal early afterglow and no emission past \nT0+129~s, with an approximate upper limit on average 75-2000 keV flux \nbetween T0+129s and of T0+259 s at the level of 5.8e-09 erg cm-2 s-1 \n(see also GCN#33431).\n\nA ToO pointed observation was carried out from 2023-03-08 11:35:00 (T0 + \n19.8 hours) to 2023-03-09 02:18:20 (T0 + 34.6 hours) with a total \nexposure time of 28.2 ks (for ISGRI). Since the observation was \nscheduled when the refined IPN localization was not yet available, the \nposition of the candidate GRB optical and X-ray afterglow ((GCN #33429, \nGCN #33439, GCN #33443, GCN #33447, GCN #33449, GCN #33459, GCN #33465)) \nwas observed at an offset of 1.3 deg, reducing somewhat the effective \nexposure of JEM-X compared to an optimal pointing.\n\nWe do not find any significant signal, and put a limit on any source \nwithin the IPN error box, including also to the possible X-ray and \noptical afterglow, at the level of 4.2e-11 erg cm-2 s-1 in the 3-200 keV \nenergy range, assuming a powerlaw spectrum with a slope of -2. This \nlimit is about 1.2 orders of magnitude lower than the detection in the \ncase of GRB 221009A.\n\nWe are grateful to the INTEGRAL Ground Segment team for the quick \nscheduling of these observations.\n\nAll of the results except PICsIT were produced MMODA platform \n(https://www.astro.unige.ch/mmoda/).",
  "circularId": 33472,
  "createdOn": 1678726470000,
  "email": "savchenk@in2p3.fr",
  "subject": "GRB 230307A: INTEGRAL upper limit on Hard X-ray afterglow",
  "submitter": "Volodymyr Savchenko at ISDC,U of Geneve  <savchenk@in2p3.fr>",
  "eventId": "GRB 230307A"
}