Context :

Aims : We present basic atmospheric parameters ( T _ { eff } , \log g , v _ { t } and [ Fe/H ] ) as well as luminosities , masses , radii and absolute radial velocities for 348 stars , presumably giants , from the \sim 1000 star sample observed within the Penn State-Toruń Centre for Astronomy Planet Search with the High Resolution Spectrograph of the 9.2 m Hobby-Eberly Telescope .
The stellar parameters ( luminosities , masses , radii ) are key ingredients in proper interpretation of newly discovered low-mass companions while a systematic study of the complete sample will create a basis for future statistical considerations concerning low-mass companions appearance around evolved low and intermediate-mass stars .

Methods : The atmospheric parameters were derived using a strictly spectroscopic method based on the LTE analysis of equivalent widths of Fe I and Fe II lines .
With existing photometric data and the Hipparcos parallaxes we estimated stellar masses and ages via evolutionary tracks fitting .
The stellar radii were calculated from either estimated masses and the spectroscopic \log g or from the spectroscopic T _ { eff } and estimated luminosities .
The absolute radial velocities were obtained by cross-correlating spectra with a numerical template .

Results : We completed the spectroscopic analysis for 332 stars of which 327 were found to be giants .
For the remaining 16 stars with incomplete data a simplified analysis was applied .
The results show that our sample is composed of stars with effective temperatures ranging from 4055 K to 6239 K , and \log g between 1.39 and 4.78 ( 5 dwarfs were identified ) .
The estimated luminosities ranging between \log L / L _ { \odot } = -1.0 and 3 lead to masses ranging from 0.6 to 3.4 M _ { \odot } .
Only 63 stars with masses larger than 2 M _ { \odot } were found .
The radii of our stars range from 0.6 to 52 R _ { \odot } with vast majority between 9-11 R _ { \odot } .
The stars in our sample are generally less metal abundant than the Sun with median [ Fe/H ] = -0.15 .
The estimated uncertainties in the atmospheric parameters were found to be comparable to those reached in other studies .
However , due to lack of precise parallaxes the stellar luminosities and , in turn , the masses are far less precise , within 0.2 M _ { \odot } in best cases , and 0.3 M _ { \odot } on average .

Conclusions :