{
  "bibcode": "2023GCN.33565....1N",
  "body": "P K. Navaneeth (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V. \nBhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao \n(IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat \nCZTI collaboration:\n\nAnalysis of AstroSat CZTI data with the CIFT framework (Sharma et al., \n2021, JApA, 42, 73) showed the detection of a long GRB 230404A which was \nalso detected by Fermi (Fermi GBM Team, GCN 33564).\n\nThe source was detected in the 20-200 keV energy range. The light curve \npeaks at 2023-04-04 23:00:07.5 UTC. The measured peak count rate \nassociated with the burst is 75 (+30, -10) counts/s above the background \nin the combined data of two quadrants (out of four), with a total of 753 \n(+275, -296) counts. The local mean background count rate was 224 (+1, \n-2) counts/s. Using cumulative rates, we measure a T90 of 29 (+10, -12) \ns.\n\nThe source was also detected in the CsI anticoincidence (Veto) detector \nin the 100-500 keV energy range. The light curve peaks at 2023-04-04 \n23:00:07.0 UTC. The measured peak count rate associated with the burst \nis 246 (+67, -54) counts/s above the background in the combined data of \nall quadrants, with a total of 3668 (+1002, -1058) counts. The local \nmean background count rate was 1491 (+6, -6) counts/s. We measure a T90 \nof 48 (+7, -12) s from the cumulative Veto light curve.\n\nWhile the two T90 measurements agree within error bars, the difference \nis higher than typical measurements. There are two possibilities for \nthis: firstly, there may be an intrinsic energy dependence in T90, with \nit being higher at higher energies. The second is that at the instant of \nthis GRB, AstroSat was relatively close to the South Atlantic Anomaly, \nwhich increased the background and hence the uncertainty in our T90 \nmeasurements.\n\nCZTI is built by a TIFR-led consortium of institutes across India, \nincluding VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research \nOrganisation funded, managed, and facilitated the project.\n\nCZTI GRB detections are reported regularly on the payload site at:\nhttp://astrosat.iucaa.in/czti/?q=grb",
  "circularId": 33565,
  "createdOn": 1680686935000,
  "email": "gauravwaratkar@iitb.ac.in",
  "subject": "GRB 230404A: AstroSat CZTI detection",
  "submitter": "Gaurav Waratkar at IIT,Bombay  <gauravwaratkar@iitb.ac.in>",
  "eventId": "GRB 230404A"
}