Van Reeth, T. ; De Cat, P. ; Van Beeck, J. ; Prat, V. ; Wright, D.J. ; Lehmann, H. ; Chené, A.-N. ; Kambe, E. ; Yang, S.L.S. ; Gentile, G. ; Joos, M.

published in Astronomy & Astrophysics, 662, pp. 1--15 (id. A58) (2022)

Abstract: Context. The TESS space mission 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 collect and reduce 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 determine the stellar pulsation frequencies from both data sets using iterative prewhitening, do asymptotic g-mode modelling of the star and investigate the corresponding spectral line profile variations using the pixel-by-pixel method. Results. We validate the pulsation frequencies from the TESS data up 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 Π 0 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.

Keyword(s): asteroseismology ; methods: observational ; stars: variables: general ; stars: oscillations (including pulsations) ; stars: individual: HD11242
DOI: 10.1051/0004-6361/202142921
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