{
  "bibcode": "2020GCN.28808....1P",
  "body": "M. Perri (ASDC), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), B. Sbarufatti\n(PSU), D.N. Burrows (PSU), J. D. Gropp (PSU), K.L. Page (U. Leicester),\nA.P. Beardmore (U. Leicester) and S. Dichiara (NASA/GSFC/UMCP) reporton\nbehalf of the Swift-XRT team:\n\nWe have analysed 6.2 ks of XRT data for GRB 201029A (Dichiara et al.\nGCN Circ. 28803), from 128 s to 34.7 ks after the  BAT trigger. The\ndata comprise 764 s in Windowed Timing (WT) mode with the remainder in\nPhoton Counting (PC) mode. The enhanced XRT position for this burst was\ngiven by Beardmore et al. (GCN Circ. 28806).\n\nThe light curve is dominated by flares. The first flare covers\n~T0+200-650 s. The second flare started at T0+1100s and was still\nongoing when the GRB entered Earth eclipse at T0+1850 s. The third\nflare began at T0+11.5 ks, was still ongoing at T0+23 ks and finished\nat some point before T0+30.5 ks, although large observing gaps in this\nwindow prevent acccurate measurements of the flare and it is possible\nthat there are multiple flares at this time rather than a single\nlong-lived flare. This behaviour, of multiple flares dominating the XRT\nlight curve for tens of kiloseconds, is reminiscent of GRBs 050904,\n121027A and 130925A (see\nhttps://www.swift.ac.uk/xrt_curves/allcurves.php for a mugshot gallery\nof all XRT GRB afterglows).\n\nThis flaring activity makes it difficult to model the underlying\nbehaviour. Excluding all of the above times, the light curve can be\nmodelled with a power-law decay with a decay index of alpha=0.79\n(+0.05, -0.06). These formal errors are likely underestimates, since\nthey depend on how accurate the estimates of flare times are, which are\nthemselves subject to proper modelling of the underlying emission.\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\t of 1.65 (+/-0.05). The\nbest-fitting absorption column is  4.9 (+/-0.3) x 10^21 cm^-2, in\nexcess of the Galactic value of 2.1 x 10^20 cm^-2 (Willingale et al.\n2013). The PC mode spectrum has a photon index of 1.97 (+/-0.12) and a\nbest-fitting absorption column of 2.9 (+/-0.5) x 10^21 cm^-2. The\ncounts to observed (unabsorbed) 0.3-10 keV flux conversion factor\ndeduced from this spectrum  is 3.7 x 10^-11 (5.4 x 10^-11) erg cm^-2\ncount^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     2.9 (+/-0.5) x 10^21 cm^-2\nGalactic foreground: 2.1 x 10^20 cm^-2\nExcess significance: 9.6 sigma\nPhoton index:\t     1.97 (+/-0.12)\n\nIf the light curve continues to decay with a power-law decay index of\n0.79, the count rate at T+24 hours will be 0.024 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 9.2 x\n10^-13 (1.3 x 10^-12) erg cm^-2 s^-1. The results of the XRT-team\nautomatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/01003002.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 28808,
  "createdOn": 1604052665000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 201029A: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 201029A"
}