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compmag: Thermal and bulk Comptonization for cylindrical accretion onto the polar cap of a magnetized neutron star

This model describes the spectral formation in the accretion column onto the polar cap of a magnetized neutron star, with both thermal and bulk Comptonization processes taken into account. The details for the method adopted for the numerical solution of the radiative transfer equation are reported in Farinelli et al. (2012, A&A, 538, A67).

This model can be used for spectral fitting of both accreting X-ray pulsars and Supergiant Fast X-ray Trasients.

par1 $kT_{bb}$, temperature of the seed blackbody spectrum (keV).
par2 $kT_e$, electron temperature of the accretion column (keV).
par3 $\tau$, vertical optical depth of the accretion column, with electron cross-section equal to $10^{-3}$ of the Thomson cross-section.
par4 $\eta$, index of the velocity profile when the accretion velocity increases towards the neutron star (valid when par8=1).
par5 $\beta_0$, terminal velocity of the accreting matter at the neutron star surface (valid when par8=1).
par6 $r_0$, radius of the accretion column in units of the neutron star Schwarzschild radius.
par7 $A$, albedo at the neutron star surface.
par8 Flag for setting the velocity profile of the accretion column (1 $\Rightarrow$ $\beta(z) = A(Z_s/Z)^{-\eta}$, where $A = \beta_0
(Z_0/Z_s)^\beta$, 2 $\Rightarrow$ $\beta(\tau) = -\alpha\tau$)
norm $(R^2_{km} /D^2_{10}$, where $R_{km}$ and $D_{10}$ are the accretion column radius in km and the source distance in units of 10 kpc, respectively.


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