{
  "submittedHow": "web",
  "bibcode": "2023GCN.34748....1R",
  "subject": "Fermi GBM Statement for Trigger 716527670/230916144",
  "submitter": "Oliver J Roberts at USRA/NASA <oliver.roberts@nasa.gov>",
  "createdOn": 1695233131673,
  "circularId": 34748,
  "body": "O.J. Roberts (USRA/NASA-MSFC), S. Bala (USRA), C. Meegan (UAH)\nreport on behalf of the Fermi GBM Team:\n\n\"At 03:27:45.98 UT on 16 September 2023, the Fermi Gamma-ray Burst Monitor (GBM)\ntriggered on trigger 716527670/230916144 as a GRB with 64% confidence). This trigger \nwas later followed up by GOTO (Vail et al., GCN 34730), identifying a candidate afterglow \n(AT 2023sva) and suggested it was the counterpart.\n\nCareful inspection of the GBM trigger by the Fermi-GBM Team identified a weak \nC1-class solar flare occurring contemporaneously at the trigger time, which dominates \nthe spectrum below 50 keV. There is approximately several hundred counts in the \n50-300 keV band over 12s, which the Team was able to localize. The on-ground calculated \nlocation using the Fermi GBM trigger data over this energy range is \nRA = 143.0, Dec = 70.5 (J2000 degrees, equivalent to J2000 9h 32m, +/- 70d 30'), with a \nstatistical uncertainty of 8.0 degrees (radius, 1-sigma containment, statistical only; there \nis additionally a systematic error which we have characterized as a core-plus-tail model, \nwith 90% of GRBs having a 3.7 deg error and a small tail suffering a larger than 10 deg \nsystematic error. [Connaughton et al. 2015, ApJS, 216, 32] ). \n\nWe note that this localization is 71 degrees from the Sun, and is quite far from the \nRA and Dec of the afterglow candidate reported by Vail et al. in GCN 34730. We therefore \nbelieve these two events to be unrelated and suggest that AT2023sva is an orphan afterglow. \nWe also note that this weak burst is contaminated by the solar flare and that any meaningful \ndata regarding the nature of this transient is likely unrecoverable.\n\nThe skymap can be found here:\nhttps://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230916144/quicklook/glg_skymap_all_bn230916144.png\n\nThe HEALPix FITS file, including the estimated localization systematic, can be found here:\nhttps://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230916144/quicklook/glg_healpix_all_bn230916144.fit\n\nThe GBM light curve can be found here:\nhttps://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230916144/quicklook/glg_lc_medres34_bn230916144.gif\""
}