TITLE: GCN CIRCULAR NUMBER: 1928 SUBJECT: GRB030226: Analysis of Chandra data DATE: 03/03/06 07:39:17 GMT FROM: Derek Fox at CIT M. Sako and D.W. Fox (Caltech) report on behalf of a larger collaboration: "We find that the detection of excess soft X-ray absorption reported by Pedersen et al. (GCN 1924) in the Chandra spectrum of GRB030226 is not required by the data. A power law of photon index 2.0 +/- 0.1 with Galactic absorption of 1.6 x 10^20 cm^-2 provides a statistically acceptable fit with chi-squared = 12.6 for 14 degrees of freedom. The 90%-confidence upper limit on the amount of absorption by neutral material at a redshift of 1.98 is N_H = 4.8 x 10^21 cm^-2 using the best current low-energy calibration. We note that our derived limit depends sensitively on the calibration below E = 0.4 keV where the response is known to be strongly time-dependent (see http://asc.harvard.edu/cal/Acis/Cal_prods/qeDeg/index.html). The power-law decay of the flux between 0.3 and 8 keV is found to be alpha_X = -3.6 +/- 1.0 over the course of the observation (epoch day 1.56 to day 2.02). This provides a statistically acceptable fit to the data (chi-squared of 7.3 for the 18 degrees of freedom of a 20-bin light curve)."