nsmaxg: neutron star with a magnetic atmosphere

 

The nsmaxg model interpolates from a grid of neutron star (NS) atmosphere spectra to produce a final spectrum that depends on the parameters listed below. 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. 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. Atmosphere models mainly depend on the surface effective temperature T_eff and magnetic field strength B and inclination Θ_B; there is also a dependence on the surface gravity g=(1+z_g)GM/R², where 1+z_g=(1-2GM/R)^-1/2 is the gravitational redshift and M and R are the NS mass and radius, respectively.

 

Two sets of models are available: one set with a single surface B and T_eff [some models allow for varying g, in the range log g (cm s^-2) = 13.6-15.4] and a set which is constructed with B and T_eff varying across the surface according to the magnetic dipole model (θ_m is the angle between the direction to the observer and the magnetic axis). Effective temperatures span the range log T_eff (K) ≈ 5.5-6.7. Models with single (B,T_eff) cover the energy range 0.05-10 keV, while models with (B,T_eff)-distributions cover the range 0.09-5 keV.

The parameters are:

 

par1	log Teff, surface (unredshifted) effective temperature
par2	M, neutron star gravitation mass (in units of Solar mass)
par3	R, neutron star radius (in km)
par4	d, distance to neutron star (in km)
par5	Switch indicating model to  use
norm	1, normalization (though not strictly correct, can be varied to change the size of the emission region, (Rem/R)2)

 

The models available by setting par5 are:

 

Switch	Element	B(1012 G)	ΘB	θm	log g (cm/s2)	log Teff	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 nsmaxg, please reference Ho, W.C.G., Potekhin, A.Y., & Chabrier, G. (2008, ApJS, 178, 102) and also Mori, K. & Ho, W.C.G. (2007, MNRAS, 377, 905) if using mid-Z models. See Ho, W.C.G. (2014, Proc. of IAUS 302, submitted) for discussion of nsmaxg and nsmax.