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We monitored the planet-bearing solar-type star HD209458 for sodiumabsorption in the region of the stellar NaI D1 line that would be indicative ofcometary activity in the system. We observed the star using the HET HRS withhigh S/N and high spectral resolution for 6 nights over the course of twoyears, from July 2001 to July 2003. From modelling we determine a 20%likelihood of a detection, based on a predicted number of comets similar tothat of the solar system. We find that our analytical method is able to recovera signal and our S/N is sufficient to detect this feature in the spectralregions on either side of the core of the D1 line, where it is most likely toappear. No significant absorption was detected for any of the nights based on a3 sigma detection limit. We derive upper limits on the column density of sodiumof < ~6 x 10^{9} cm^{-2} for a signal in the region around the line core and <\~2 x 10^{10} cm^{-2} for a signal in the core of the photospheric D1 line.These numbers are consistent with the sodium released in a single periodiccomet in our own system, though higher S/N may be necessary to uncover a signalin the core of the D1 line. Implications for cometary activity in the HD209458system are discussed.Comment: 19 pages, 8 figures, ApJ in pres

A Search for Sodium Absorption from Comets around HD 209458