{
  "bibcode": "2025GCN.40255....1M",
  "eventId": "GRB 250424A",
  "circularId": 40255,
  "subject": "GRB 250424A: Swift-BAT refined analysis",
  "submittedHow": "web",
  "submitter": "Rahul Gupta at NASA GSFC <rahul.gupta@nasa.gov>",
  "body": "C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), \nS. B. Cenko (GSFC), R. Gupta (GSFC),\nH. A. Krimm (NSF), S. Laha (GSFC/UMBC),\nA. Y. Lien (U Tampa), M. J. Moss (GSFC),\nD. M. Palmer (LANL), T. Parsotan (GSFC),\nD. Sadaula (GSFC/UMBC), T. Sakamoto (AGU)\n(i.e. the Swift-BAT team):\n \nUsing the data set from T-239 to T+963 sec from the recent telemetry downlink,\nwe report further analysis of BAT GRB 250424A (trigger #1306404)\n(Cenko, et al., GCN Circ. 40224).  The BAT ground-calculated position is\nRA, Dec = 217.528, -35.025 deg which is \n   RA(J2000)  =  14h 30m 06.7s \n   Dec(J2000) = -35d 01' 30.6\" \nwith an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).\nThe partial coding was 39%.\n \nThe mask-weighted BAT light curve of the burst (began during a slew) shows a faint precursor emission followed by a bright main pulse. \nT90 (15-350 keV) is 19.03 +- 1.06 sec (estimated error including systematics), with the T90 starting at T0-20.76 sec due to the slew-delayed T0.\n\n \nThe time-averaged spectrum from T-38.75 to T+262.67 sec is best fit by a power law\nwith an exponential cutoff.  This fit gives a photon index 1.54 +- 0.13, \nand Epeak of 106.5 +- 33.7 keV (chi squared 47.05 for 56 d.o.f.).  For this\nmodel the total fluence in the 15-150 keV band is 3.2 +- 0.1 x 10^-05 erg/cm2\nand the 1-sec peak flux measured from T-15.38 sec in the 15-150 keV band is\n47.0 +- 1.3 ph/cm2/sec.  A fit to a simple power law gives a photon index\nof 1.79 +- 0.03 (chi squared 58.54 for 57 d.o.f.).  All the quoted errors\nare at the 90% confidence level. \n \nThe results of the batgrbproduct analysis are available at\nhttps://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1306404",
  "format": "text/plain",
  "createdOn": 1745707718657
}