Chromospheres and mass loss in metal-deficient giant stars

Semiempirical atmospheric models indicate that the characteristic emission in the wings of the Hα line observed in Population II giant stars can arise naturally within static chromospheres. Radial expansion gives an asymmetric, blueshifted Hα core accompanied by greater emission in the red line wing than in the blue wing. Wind models with extended atmospheres suggest mass loss rates much smaller than 2×10⁻⁹M_sun; yr⁻¹. Thus Hα provides no evidence that steady mass loss can significantly affect the evolution of stars on the red giant branch of globular clusters.