HI Lyman-alpha equivalent widths of stellar populations
  We have compiled a library of stellar Lyman-alpha equivalent widths in O and
B stars using the model atmosphere codes CMFGEN and TLUSTY, respectively. The
equivalent widths range from about 0 to 30 \AA in absorption for early-O to
mid-B stars. The purpose of this library is the prediction of the underlying
stellar Lyman-alpha absorption in stellar populations of star-forming galaxies
with nebular Lyman-alpha emission. We implemented the grid of individual
equivalent widths into the Starburst99 population synthesis code to generate
synthetic Lyman-alpha equivalent widths for representative star-formation
histories. A starburst observed after 10 Myr will produce a stellar Lyman-alpha
line with an equivalent width of $\sim$ -10$\pm$4 \AA in absorption for a
Salpeter initial mass function. The lower value (deeper absorption) results for
an instantaneous burst, and the higher value (shallower line) for continuous
star formation. Depending on the escape fraction of nebular Lyman-alpha
photons, the effect of stellar Lyman-alpha on the total profile ranges from
negligible to dominant. If the nebular escape fraction is 10%, the stellar
absorption and nebular emission equivalent widths become comparable for
continuous star formation at ages of 10 to 20 Myr.
