A new soft X-ray spectral model for polars with an application to AM Herculis

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Table 1

Parameters of spectral fits to the mean September 2000 Chandra LETG and April 1991 ROSAT PSPC spectra of AM Her.

Model	N_H¹	kT	k T₀	F_bb		f₉₃₀		χ²/d.o.f.
	(10¹⁹ H-atoms cm^-2)	(eV)	(eV)	(10^-9 erg cm^-2 s^-1)		(10^-13 erg cm^-2 s^-1 Å^-1)

(a) Chandra LETG, September 2000:
1 BB+CF ²	4.35 ± 0.10	32.3 ± 0.3		1.15 ± 0.05		0.11 ± 0.01		297.1 / 63³
2 BB+CF²	6.00 ± 0.44	24.7 ± 1.9		2.60 ± 0.60		0.50 ± 0.20		63.8 / 61³
		41.5 ± 2.1
10 BB+CF²	6.71 ± 0.00	12.5...57.5		5.57 ± 0.85	3.95 ± 0.25	3.00 ± 0.93	1.18 ± 0.18	63.3 / 56³
EXP+CF²	6.57 ± 0.11		3.45 ± 0.04	5.74 ± 0.30	4.14 ± 0.20	4.06 ± 0.25	1.33 ± 0.08	64.2 / 63³
(b) ROSAT PSPC, April 1991:
1 BB+CF+RL⁴	4.25 ± 0.15	30.7 ± 0.3		1.29 ± 0.06		0.14 ± 0.01		50.6 / 66⁵
EXP+CF+RL⁴	6.72 ± 0.17	28.5⁶	3.43 ± 0.06	5.47 ± 0.33	4.22 ± 0.10	3.37 ± 0.29	1.37 ± 0.09	45.5 / 65⁵

Notes. The upper index “15 eV” refers to spectral components with blackbody temperatures kT > 15 eV. BB = blackbody model, CF = cooling-flow model, EXP = exponential model (Eq. (1)), RL = “He-like emission lines” excluded from the fit to the Chandra LETG spectrum.

⁽¹⁾

N_H is for a hydrogen ionization x_H = 0.25.

⁽²⁾

Fit excludes the helium-like emission lines.

⁽³⁾

χ² and the number of d.o.f. refer to the 0.10–0.50 keV energy interval.

⁽⁴⁾

RL component included in the fit.

⁽⁵⁾

χ² and d.o.f. refer to 0.09–2.00 keV.

⁽⁶⁾

Average count rate-weighted blackbody temperature.

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