Emitted spectra from a nonmagnetic hydrogen atmosphere of a neutron star.

The model provides the spectra emitted from a nonmagnetic hydrogen atmosphere of a neutron star. The model spectra in a 0 - 20 keV range of (unredshifted) photon energy are computed on a grid of surface gravity accelerations log(g)=13.7 - 14.9 (in cgs units) and effective temperatures T = 0.5 - 10 MK. For a given set of the fitting parameters, the surface gravity g and the gravitational redshift z are derived from the mass M and radius R of the star. The trial spectra are computed using a linear interpolation between the nearest model spectra on the T-log(g) grid, and the boundaries of the energy bins and the number of photons in each bin are divided by (1+z). The details of the model can be found in Suleimanov et al. 2016 (A&A, submitted) and Klochkov et al. 2015 A&A 573, 53.

The fitting parameters of the model are listed below:

par1 = Effective temperature T (MK)

par2 = Neutron star mass M (M_sol)

par3 = Neutron star radius R (km)

par4 = Normalization K = A/(d_10kpc)^2

where d_10kpc is the distance to the source in units of 10 kpc and A characterizes the fraction of the star surface emitting the radiation (A=1 corresponds to the case when the radiation is emitted from the entire surface).

To use the model do the following steps:

1) extract hatm.tar.gz, which will create a directory named "hatm" containing all necessary files. To compile and to use the model, a writing access to the directory is necessary!

2) to compile the model, launch XSPEC 12 and execute the following command XSPEC12> initpackage mypackage model.dat /full-path-to-hatm/hatm/

3) load the compiled model package with "lmod" command: XSPEC12> lmod mypackage /full-path-to-hatm/hatm/

4) Copy the directory hatm/hatm_tables to $HEADAS/../spectral/modelData/ or, alternatively, use the "xset" command of XSPEC to set the HATM variable to the full path to the directory containing the "hatm_tables" subdirectory:

XSPEC12> xset HATM /full-path-to/hatm/ (Note: /full-path-to/hatm/ should *not* include the "hatm_tables" itself).

The model is now available under the name "hatm".

Please send any questions and comments to suleimanov@astro.uni-tuebingen.de or klochkov@astro.uni-tuebingen.de