{
"subject": "GRB030226: Analysis of Chandra data",
"bibcode": "2003GCN..1928....1S",
"createdOn": 1046936357000,
"circularId": 1928,
"submitter": "Derek Fox at CIT ",
"email": "derekfox@astro.caltech.edu",
"body": "M. Sako and D.W. Fox (Caltech) report on behalf of a larger\ncollaboration: \n\n\"We find that the detection of excess soft X-ray absorption reported\nby Pedersen et al. (GCN 1924) in the Chandra spectrum of GRB030226 is\nnot required by the data. A power law of photon index 2.0 +/- 0.1\nwith Galactic absorption of 1.6 x 10^20 cm^-2 provides a statistically\nacceptable fit with chi-squared = 12.6 for 14 degrees of freedom. The\n90%-confidence upper limit on the amount of absorption by neutral\nmaterial at a redshift of 1.98 is N_H = 4.8 x 10^21 cm^-2 using the\nbest current low-energy calibration. We note that our derived limit\ndepends sensitively on the calibration below E = 0.4 keV where the\nresponse is known to be strongly time-dependent (see\nhttp://asc.harvard.edu/cal/Acis/Cal_prods/qeDeg/index.html). The\npower-law decay of the flux between 0.3 and 8 keV is found to be\nalpha_X = -3.6 +/- 1.0 over the course of the observation (epoch day\n1.56 to day 2.02). This provides a statistically acceptable fit to\nthe data (chi-squared of 7.3 for the 18 degrees of freedom of a 20-bin\nlight curve).\""
}