Pressure Broadening of Absorption Lines in Neutron Star Atmospheres and Prospects for Measuring Neutron Star Masses and Radii

摘要

At the very high densities encountered in neutron star atmospheres, the pressure broadening of heavy-ion absorption lines due to the Stark effect should be appreciable. Simple scaling arguments suggest that the line widths should be measurable in the near future with the next generation X-ray spectrometers. A simultaneous measurement of the gravitational redshift and of the acceleration of gravity at the surface will produce separate (though coupled) measurements of stellar mass and radius. Although the procedure to measure the acceleration of gravity from a line profile is of course completely analogous to that used in classical stellar spectroscopy, it is because the redshifts in neutron stars are large, and separately measurable, that the spectroscopy yields both the mass and the radius.