Context. The Transiting Exoplanet Survey Satellite (TESS) provides us with high-precision photometric observations of large numbers of bright stars over more than 70% of the entire sky, allowing us to revisit and characterise well-known stars.
Aims: We aim to conduct an asteroseismic analysis of the γ Doradus (γ Dor) star HD 112429 using both the available ground-based spectroscopy and TESS photometry, and assess the conditions required to measure the near-core rotation rate and buoyancy travel time.
Methods: We collected and reduced the available five sectors of short-cadence TESS photometry of this star, as well as 672 legacy observations from six medium- to high-resolution ground-based spectrographs. We determined the stellar pulsation frequencies from both data sets using iterative prewhitening, did asymptotic g mode modelling of the star, and investigated the corresponding spectral line profile variations using the pixel-by-pixel method.
Results: We validate the pulsation frequencies from the TESS data down to S/N ≥ 5.6, confirming recent reports in the literature that the classical criterion S/N ≥ 4 does not suffice for space-based observations. We identify the pulsations as prograde dipole g modes and r-mode pulsations, and measure a near-core rotation rate of 1.536 (3) d−1 and a buoyancy travel time Π0 of 4190 (50) s. These results are in agreement with the observed spectral line profile variations, which were qualitatively evaluated using a newly developed toy model. We establish a set of conditions that have to be fulfilled for an asymptotic asteroseismic analysis of g-mode pulsators. In the case of HD 112429, two TESS sectors of space photometry suffice.
Conclusions: Although a detailed asteroseismic modelling analysis is not viable for g-mode pulsators with only short or sparse light curves of space photometry, it is possible to determine global asteroseismic quantities for a subset of these stars. Thanks to the ongoing TESS mission, this will allow us to characterise many more stars than only those with years of data.
Astronomy and Astrophysics
- Pub Date:
- June 2022
- methods: observational;
- stars: variables: general;
- stars: oscillations;
- stars: individual: HD 112429;
- Astrophysics - Solar and Stellar Astrophysics
- 15 pages, 13 figures, 4 tables. Accepted for publication in Astronomy and Astrophysics