A SPECTROSCOPIC STUDY OF PULSATIONS IN γ DORADUS STARS

Two candidate γ Doradus stars are analysed: HD 103257 and HD 109799. Over 250 spectra were gathered for analysis using the HERCULES spectrograph at the University of Canterbury Mt John Observatory. The spectra for each star were cross-correlated with synthetic spectra to produce line profiles and augmented with photometric data from the WASP archive and HIPPARCOS catalogue for frequency and mode analysis. Three pulsation frequencies were identified for HD 103257: 1.22496 ± 0.00001 d^(-1), 1.14569 ± 0.00002 d^(-1) and 0.67308 ± 0.00004 d^(-1), explaining 66.6% of the variation across the line profiles. The frequencies were characterised with best-fit modes of (l, m) = (1, 1), (1, 1) and (3, -2) respectively. The inclination of the rotation axis and the radius were best-fit to i = 86.4° and R = 2.6 R_⊙, while a zero-point fit yielded a vsini of 71.5 km s^(-1). Three pulsation frequencies were identified for HD 109799: 1.48679 ± 0.00002 d^(-1), 1.25213 ± 0.00002 d^(-1) and 0.92184 ± 0.00004 d^(-1) , explaining 39.3% of the variation across the line profiles. The frequencies yielded individual mode fits of modes (l, m) = (1, 1), (1, 1) and (3, 2). The rotational axis for HD 109799 to the range i = 65° - 70° with a zero-point fitted vsini of 40.2 km s^(-1). Based on observations of frequencies and modes characteristic of the class, HD 103257 and HD 109799 can now be categorised as bona fide γ Doradus stars. The results within this thesis will be of service in the future development of theoretical models pertaining to the interiors of γ Doradus stars.