Spectroscopic frequency and mode identification of γ Doradus stars HD 109799 and HD 103257

Abstract

ABSTRACT Following frequency and mode identification of two candidate γ Doradus stars, HD 103257 and HD 109799, both can be categorized as bona-fide members of the class. Over 250 high-resolution spectra of the two stars were collected at University of Canterbury Mount John Observatory (UCMJO) using the High Efficiency and Resolution Canterbury University Large Echelle Spectrograph (HERCULES) spectrograph. The spectra were cross-correlated with a synthetic δ-function template to produce line-profiles and further augmented with high-quality photometry from the Transiting Exoplanet Survey Satellite (TESS) mission, the Wide Angle Search for Planets (WASP) archive, and HIPPARCOS catalogue for frequency and mode analysis. Frequency analysis was carried out using FAMIAS and SigSpec. Two pulsation frequencies were identified in the spectra for HD 103257: 1.22496 ± 0.00001 and 1.14569 ± 0.00002 d−1, explaining 58.9 ${{\ \rm per\ cent}}$ of the variation across the line profiles. Both frequencies were characterized with best-fitting modes of (ℓ, m) = (1, 1). Two pulsation frequencies were identified in the spectra for HD 109799: 1.48679 ± 0.00002 and 1.25213 ± 0.00002 d−1, explaining 32.6 ${{\ \rm per\ cent}}$ of the variation across the line profiles. Both frequencies also yielded individual mode fits of modes (ℓ, m) = (1, 1). The excellent quality photometry from TESS observations has proven complementary to the work herein, and will provide a meaningful opportunity for deeper analysis of additional stars in the HERCULES catalogue. This will be a key component in the continued development of models relating to the processes within γ Doradus stars.