The near-core rotation of HD 112429. A γ Doradus star with TESS photometry and legacy spectroscopy

Creators: 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.

Abstract

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.

Additional Information

© ESO 2022. Received 15 December 2021 / Accepted 21 March 2022. We thank the referee for their positive report and useful comments which improved the quality of the paper. T.V.R. gratefully acknowledges a postdoctoral fellowship from the Research Foundation Flanders (FWO) with grant agreement N° 12ZB620N. J.V.B. acknowledges receiving support from the Research Foundation Flanders (FWO) under grant agreement N° V421221N. The research leading to these results received partial funding from the KU Leuven Research Council (grant C16/18/005: PARADISE, with PI Conny Aerts). A.N.C. is supported by the international Gemini Observatory, a program of NSF's NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation, on behalf of the Gemini partnership of Argentina, Brazil, Canada, Chile, the Republic of Korea, and the United States of America. This paper includes data collected with the TESS mission, obtained from the MAST data archive at the Space Telescope Science Institute (STScI). Funding for the TESS mission is provided by NASA's Explorer Program. We thank the whole team for the development and operations of the mission. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. We are also very grateful to Bill Paxton, Rich Townsend and their respective teams for the development and maintenance of the open-source stellar evolution code MESA and the open-source stellar pulsation code GYRE. We would also like to thank Christoffel Waelkens and Roy Østensen for their contributions to the multi-site spectroscopic observation campaign, and Andrew Tkachenko for useful discussions and for his work on the code for least-squares deconvolution profile computation. This work was also based on observations made with multiple spectrographs, including the SOPHIE spectrograph at the 1.93-m telescope at Observatoire de Haute-Provence (CNRS/OAMP), France; the McKellar spectrograph at the 1.2-m Telescope at the Dominion Astrophysical Observatory, NRC Herzberg, Programs in Astronomy and Astrophysics, National Research Council of Canada; the HERMES spectrograph, which is supported by the Research Foundation – Flanders (FWO), Belgium, the Research Council of KU Leuven, Belgium, the Fonds National de la Recherche Scientifique (F.R.S.-FNRS), Belgium, the Royal Observatory of Belgium, the Observatoire de Genève, Switzerland and the Thüringer Landessternwarte Tautenburg, Germany, and installed at the Mercator telescope, operated by the Flemish Community, on the island of La Palma at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias (IAC); the HIDES spectrograph at the 1.88-m telescope at the Okayama Astrophysical Observatory in Japan; the Sandiford Cassegrain Echelle Spectrograph at the Otto Struve telescope at the McDonald Observatory of the University of Texas at Austin; the TCES spectrograph at the 2.0-m Alfred Jensch Telescope at the Türinger Landessternwarte in Tautenburg, Germany. This research made use of the SIMBAD database, operated at CDS, Strasbourg, France, the SAO/NASA Astrophysics Data System, the VizieR catalogue access tool, CDS, Strasbourg, France, and Lightkurve, a Python package for Kepler and TESS data analysis (Lightkurve Collaboration 2018).

Attached Files

Published - aa42921-21.pdf

Accepted Version - 2203.11071.pdf

Files

2203.11071.pdf

Files (4.2 MB)

Name	Size	Download all
2203.11071.pdf md5:b0774f0098c1f369c746b5ace310b980	2.1 MB	Preview Download
aa42921-21.pdf md5:825731f5163ad1dc5d0d0bb6891fc5f8	2.1 MB	Preview Download

Additional details

	All versions	This version
Views	0	0
Downloads	0	0
Data volume	0 Bytes	0 Bytes