Emitted spectra from a nonmagnetic carbon
atmosphere of a neutron star.
NOTE: This model is now in the Xspec release and this page is superceded by the Xspec manual
The model provides the spectra emitted from a nonmagnetic carbon
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 = 1 - 4 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.
The number of photons in each bin are divided by (1+z). This is an
updated version of the models presented in
Suleimanov et al. 2014, ApJS 210, 13.
The details can be found in Suleimanov, Klochkov et al. 2016 (A&A, submitted).
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
To use the model do the following steps:
1) extract carbatm.tar.gz, which
will create a directory named "carbatm" 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-carbatm/carbatm/
3) load the compiled model package with "lmod" command:
XSPEC12> lmod mypackage /full-path-to-carbatm/carbatm/
4) Copy the directory carbatm/catm_tables to
or, alternatively, use the "xset" command of XSPEC to set the
CARBATM variable to the full path to the directory containing
the "catm_tables" subdirectory:
XSPEC12> xset CARBATM /full-path-to/carbatm/
(Note: /full-path-to/carbatm/ should *not* include the "catm_tables" itself).
The model is now available under the name "carbatm".
Please send any questions and comments to
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Last modified: Tuesday, 14-Feb-2023 16:41:51 EST