Analytical fits to theoretical spectra of X-ray burst sources: a hint on the surface gravity.
Abstract
Simple analytic formulae have been developed to fit the existing grid of X-ray spectra of very hot neutron star atmospheres. Model atmospheres analysed here were computed in both the radiative and hydrostatic equilibrium, and included precisely the effects of relativistic Compton scattering, The grid of fitted models covers the range of T_eff_ from 8x10^6^K up to 3x10^7^K, and logg=15.0 down to the Eddington limit, but was restricted to fully ionized hydrogen/helium gas with the He number abundance N_He_/N_H_=0.11. Both T_eff_ and logg in the above models are defined on the surface of a neutron star. Fitting parameters given in the paper define the relation T_c_-T_eff_ between the observed color temperature of a general X-ray burst and the effective temperature, and depend also on the surface gravity logg and the general relativistic redshift. Results of this paper can be used for the estimates of both T_eff_ and logg directly from the observed spectra of X-ray bursts, as long as the composition of accreted matter is restricted to H and He alone, and the redshift correction is negligible or at least can be guessed.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- April 1997
- Bibcode:
- 1997A&A...320..177M
- Keywords:
-
- X-RAYS: GENERAL;
- STARS: NEUTRON;
- X-RAYS: BURSTS