Ratio of color and effective temperatures in X-ray burst spectra

Abstract

We present model atmospheres and theoretical spectra for X-ray bursters. Our models include the effects of Compton scattering on free electrons. The atmospheres have compositions that are mixtures of hydrogen, helium, and iron. For our models the ratio of color temperature, $T_c$, to effective temperature, $T_{eff}$, is in the range 1.2 - 1.8. This ratio depends on $T_{eff}$, surface gravity, and iron abundance. For fixed $T_{eff}$ and surface gravity, models with non-zero iron abundance exhibit values of $T_c/T_{eff}$ that are slightly lower than pure hydrogen-helium models.