  HD 149026b is a short-period, Saturn-mass planet that transits a metal-rich
star. The planet's radius, determined by photometry, is remarkably small
compared to other known transiting planets, with a heavy-element core that
apparently comprises ~70% of the total planet mass. Time-series spectra were
obtained at Keck before and during transit in order to model the
Rossiter-McLaughlin effect. Here we make use of these observations to carry out
a differential comparison of spectra obtained in and out of transit to search
for signatures of neutral atomic lithium and potassium from the planet
atmosphere. No signal was detected at the 2% level; we therefore place upper
limits on the column density of these atoms.
