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Home All issues Volume 498 / No 1 (April IV 2009) A&A, 498 1 (2009) 195-207 Full HTML
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Table 3:

Temperature (keV) and radius (km) evolution with time of $BB_{\rm cold}$ and $BB_{\rm hot}$ in the 2BB model, with uncertainties at 1$\sigma $ confidence level (68%).
Epoch $kT_{\rm cold}$ $R_{\rm cold}$ $kT_{\rm hot}$ $R_{\rm hot}$
  keV km keV km
Sep. 03 $0.275\pm0.009$ $5.8\pm0.4$ $0.685\pm0.005$ $1.54\pm0.03$
Mar. 04 $0.275\pm0.009$ $5.0\pm0.4$ $0.699\pm0.009$ $1.07\pm0.03$
Sep. 04 $0.251\pm0.005$ $5.6\pm0.4$ $0.677\pm0.005$ $0.85\pm0.02$
Mar. 05 $0.225\pm0.004$ $6.0\pm0.4$ $0.597\pm0.006$ $0.71\pm0.02$
Sep. 05 $0.205\pm0.004$ $6.6\pm0.4$ $0.54\pm0.01$ $0.51\pm0.04$
Mar. 06 $0.192\pm0.004$ $7.2\pm0.5$ $0.50\pm0.02$ $0.42\pm0.05$
Sep. 06 $0.177\pm0.004$ $8.2\pm0.5$ $0.36\pm0.02$ $0.8 \pm0.1$
Mar. 07 $0.170\pm0.005$ $9.0\pm0.7$ $0.33\pm0.02$ $1.0 \pm0.2$
Sep. 07 $0.167\pm0.004$ $9.3\pm0.7$ $0.33\pm0.01$ $0.9 \pm0.1$
Given the stability of both the flux and spectrum over the last three observations (less than 8% variation in flux in the 0.6-10 keV energy band; September 2006-2007), we merged the source photon lists to obtain a higher S/N spectrum. The calibration of the PN instrument has proved to be also very stable (Krisch et al. 2005). The analysis of the merged spectrum significantly improved the determination of the spectral parameters as compared to each single spectrum (see Table 4). Furthermore, the hotter BB component remained statistically non-significant also in the merged spectrum. We could thus obtain a more accurate (3$\sigma $) upper limit on its flux: $F_{\rm BBhot}<4.5\times10^{-14}~\ergscm2$ in the 0.6-10 keV energy band.

Source LaTeX | All tables | In the text

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