We use new high-dispersion spectroscopic and precise photometric observations to identify 12 new γ Doradus stars. Two of the 12 systems are double-lined binaries that show obvious velocity variability. Five other stars have metallic lines with composite profiles characterized by a narrow feature near the center of each broad component. Spectrograms of the Hα line indicate that all five stars are binaries rather than shell stars. The remaining five stars in our sample are probably single. All 12 stars are photometrically variable with amplitudes between 6 and 87 mmag in Johnson B and periods between 0.3 and 1.2 days. Four stars are monoperiodic; the rest have between two and five independent periods. The variability at all periods approximates a sinusoid. Although many of the stars lie within the δ Scuti instability strip, none exhibit the higher frequency variability seen in δ Scuti stars. We have increased the sample of known γ Doradus stars by 40% and revised the positions of a number of variables in the H-R diagram by accounting for duplicity. Our list of 42 confirmed γ Doradus variables gives some of their properties. All are dwarfs or subgiants and lie within a well-defined region of the H-R diagram that overlaps the cool edge of the δ Scuti instability strip. We compare the observed location of the γ Doradus variables with a recently published theoretical γ Doradus instability strip and find good agreement.
Gregory W. Henry and Francis C. Fekel 2003 AJ 126 3058