nsa: neutron star atmosphere

This model provides the spectra in the X-ray range (0.05–10 keV) emitted from a hydrogen atmosphere of a neutron star. There are three options : nonmagnetized (B $< 10^8 - 10^9$ G) with a uniform surface (effective) temperature in the range of $\log T_{eff}(K) = 5.0 - 7.0$; a field B = $10^{12}$ G with a uniform surface (effective) temperature in the range of $\log T_{eff}(K) = 5.5 - 6.8$; a field B = $10^{13}$ G with a uniform surface (effective) temperature in the range of $\log T_{eff}(K) = 5.5 - 6.8$. The atmosphere is in radiative and hydrostatic equilibrium; sources of heat are well below the atmosphere. The Comptonization effects (significant at $T_{eff} > 3\times 10^6$ K) are taken into account. The model spectra are provided as seen by a distant observer, with allowance for the GR effects. The user is advised to keep $M_{ns}$ and $R_{ns}$ fixed and fit the temperature and the normalization. MagField must be fixed at one of 0, $10^{12}$, or $10^{13}$.

The values of the effective temperature and radius as measured by a distant observer (“values at infinity”) are :

$$T^{\inf}_{eff} = T_{eff} \times g_r R^{\inf}_{ns} = R_{ns}/g_r$$

where

$$g_r = \sqrt{1 - 2.952\times M_{ns}/R_{ns}}$$

is the gravitational redshift parameter.

Please send your comments/questions to Slava Zavlin (vyacheslav.zavlin@msfc.nasa.gov) and/or George Pavlov (pavlov@astro.psu.edu). If you publish results obtained using these models, please reference Zavlin, Pavlov & Shibanov (1996) for nonmagnetic models, and Pavlov et al. (1995) for magnetic models.

par1	$\log T_{eff}$, (unredshifted) effective temperature
par2	$M_{ns}$, neutron star gravitational mass (in units of solar mass)
par3	$R_{ns}$, neutron star radius (in km)
par4	neutron star magnetic field strength (0, $10^{12}$, or $10^{13}$ G)
norm	$1/D^2$, where $D$ is the distance of the object in pc.

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Last modified: Wednesday, 12-Mar-2025 17:05:24 EDT