nsmax: Neutron Star Magnetic Atmosphere

This model has been superseded by nsmaxg.

This model interpolates from a grid of neutron star (NS) atmosphere spectra to produce a final spectrum that depends on the parameters listed below. The atmosphere spectra are obtained using the latest equation of state and opacity results for a partially ionized, strongly magnetized hydrogen or mid-Z element plasma. The models are constructed by solving the coupled radiative transfer equations for the two photon polarization modes in a magnetized medium, and the atmosphere is in radiative and hydrostatic equilibrium. The atmosphere models mainly depend on the surface effective temperature $T_{eff}$ and magnetic field strength $B$ and inclination $\Theta_B$; there is also a dependence on the surface gravity $g = (1+z_g)GM/R^2$, where $1+z_g = \sqrt{1-2GM/R}$ is the gravitational redshift and $M$ and $R$ are the NS mass and radius, respectively.

Two sets of models are given: one set with a single surface $B$ and $T_{eff}$ and a set which is constructed with $B$ and $T_{eff}$ varying across the surface according to the magnetic dipole model (for the latter, $\theta_m$ is the angle between the direction to the observer and the magnetic axis). The effective temperatures span the range $\log T_{eff} = 5.5 - 6.8$ for hydrogen and $\log T_{eff} = 5.8 - 6.9$ for mid-Z elements. The models with single ($B$,$T_{eff}$) cover the energy range 0.05–10 keV, while the models with ($B$,$T_{eff}$)-distributions cover the range 0.09–5 keV.

par1	$\log T_{eff}$, surface (unredshifted) effective temperature
par2	$1 + z_g$, gravitational redshift
par3	switch indicating model to use
norm	$A = (R_{em}/d)^2$, normalization, where $R_{em}$ is the size (in km) of the emission region and $d$ is the distance (kpc) to the object Note: A is added automatically by XSPEC.

The models available by setting par3 are:

Switch	Element	$B$($10^{12}$ G)	$\Theta_B$	$\theta_m$	$\log g$ (cm/s$^2$)	$\log T_{eff}$	$E$ (keV)
1000	H	0.01	0	N/A	2.4	5.5 – 6.7	0.05 - 10
1060	H	0.04	0	N/A	2.4	5.5 – 6.7	0.05 - 10
1085	H	0.07	0	N/A	2.4	5.5 – 6.7	0.05 - 10
1100	H	0.1	0	N/A	2.4	5.5 – 6.7	0.05 - 10
1200	H	1.0	0	N/A	0.4 – 2.5	5.5 – 6.7	0.05 - 10
1230	H	2.0	0	N/A	2.4	5.5 – 6.8	0.05 - 10
1260	H	4.0	0	N/A	2.4	5.5 – 6.8	0.05 - 10
1280	H	7.0	0	N/A	2.4	5.5 – 6.8	0.05 - 10
1300	H	10.0	0	N/A	0.4 – 2.5	5.5 – 6.7	0.05 - 10
1330	H	20.0	0	N/A	2.4	5.6 – 6.8	0.05 - 10
1350	H	30.0	0	N/A	2.4	5.7 – 6.8	0.05 - 10
1211	H	1.26	0	N/A	1.6	5.5 – 6.8	0.05 - 10
1281	H	7.0	0	N/A	1.6	5.5 – 6.8	0.05 - 10
12006	C	1.0	0	N/A	2.4	5.8 – 6.9	0.05 - 10
13006	C	10.0	0	N/A	2.4	5.8 – 6.9	0.05 - 10
12008	O	1.0	0	N/A	2.4	5.8 – 6.9	0.05 - 10
13008	O	10.0	0	N/A	2.4	5.8 – 6.9	0.05 - 10
12010	Ne	1.0	0	N/A	2.4	5.8 – 6.9	0.05 - 10
13010	Ne	10.0	0	N/A	2.4	5.8 – 6.9	0.05 - 10
123100	H	1.0 – 1.82	0-90	0	1.6	5.5 – 6.8	0.09 - 5
123190	H	1.0 – 1.82	0-90	90	1.6	5.5 – 6.8	0.09 - 5
130100	H	5.5 – 10.0	0-90	0	1.6	5.5 – 6.8	0.09 - 5
130190	H	5.5 – 10.0	0-90	90	1.6	5.5 – 6.8	0.09 - 5

If you publish results obtained using nsmax, please reference Ho, Potekhin & Chabrier (2008) and also Mori & Ho (2007) if using the mid-Z models. See Ho (2014) for discussion of nsmaxg and nsmax.

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