Table 3: Relevant absorption edges in the RGS spectrum of Cyg X-2. The energy, the corresponding wavelength, and the optical depth ( $\tau$ ) were obtained from the data. The equivalent total hydrogen column density $N_{\rm H}$ was derived from the ISM abundances of Wilms et al. (2000). These are to be compared with the best-fit $\mbox{$N_{\rm H}$ } =(2.20\pm 0.02)\times 10^{21}\ {\rm cm}^{-2}$ , measured by RGS. Errors are given at 90% confidence level.
Element Energy Wavelength $\tau$ $N_{\rm H}$

keV Å $10^{21}\ {\rm cm}^{-2}$

N K-shell 0.409 (fixed) 30.31 $0.15\pm0.06$ $2.7\pm1.1$

O K-shell 0.543 (fixed) 22.83 0.81 $\pm0.10$ $2.8\pm0.8$

Fe L-shell $0.706\pm0.01$ $17.56\pm0.02$ $0.13\pm0.01$ $2.8\pm0.2$

Ne K-shell 0.869^+0.02_-0.06 14.26^+0.10_-0.03 $0.06\pm0.03$ $1.8\pm0.9$

**Table 3:** Relevant absorption edges in the RGS spectrum of Cyg X-2. The energy, the corresponding wavelength, and the optical depth ( $\tau$ ) were obtained from the data. The equivalent total hydrogen column density $N_{\rm H}$ was derived from the ISM abundances of Wilms et al. (2000). These are to be compared with the best-fit $\mbox{$N_{\rm H}$ } =(2.20\pm 0.02)\times 10^{21}\ {\rm cm}^{-2}$ , measured by RGS. Errors are given at 90% confidence level.
Element	Energy	Wavelength	$\tau$	$N_{\rm H}$
	keV	Å		$10^{21}\ {\rm cm}^{-2}$
N K-shell	0.409 (fixed)	30.31	$0.15\pm0.06$	$2.7\pm1.1$
O K-shell	0.543 (fixed)	22.83	0.81 $\pm0.10$	$2.8\pm0.8$
Fe L-shell	$0.706\pm0.01$	$17.56\pm0.02$	$0.13\pm0.01$	$2.8\pm0.2$
Ne K-shell	0.869^+0.02_-0.06	14.26^+0.10_-0.03	$0.06\pm0.03$	$1.8\pm0.9$

Source LaTeX | All tables | In the text

	1 Introduction
	2 The halo theory
	3 Data analysis
	4 The analysis of the scattering halo
	5 The halo modeling
	6 Discussion
	7 Conclusions
	References