KIC 7955301: A hierarchical triple system with eclipse timing variations and an oscillating red giant

Patrick Gaulme, Tamás Borkovits, Thierry Appourchaux, Krešimir Pavlovski, Federico Spada, Charlotte Gehan, Joel Ong, Andrea Miglio, Andrew Tkachenko, Benoît Mosser, Mathieu Vrard, Mansour Benbakoura, Stephen Drew Chojnowski, Jean Perkins, Anne Hedlund, Jason Jackiewicz

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)
37 Downloads (Pure)

Abstract

KIC 7955301 is a hierarchical triple system with clear eclipse timing and depth variations that was discovered by the Kepler satellite during its original mission. It is composed of a non-eclipsing primary star at the bottom of the red giant branch (RGB) on a 209-day orbit with a K/G-type main-sequence (MS) inner eclipsing binary (EB), orbiting in 15.3 days. This system was noted for the large amplitude of its eclipse timing variations (ETVs, over 4 h), and the detection of clear solar-like oscillations of the red-giant (RG) component, including p-modes of degree up to l = 3 and mixed l = 1 modes. The system is a single-lined spectroscopic triple, meaning that only spectral lines from the RG are detected. We performed a dynamical model by combining the 4-year-long Kepler photometric data, ETVs, and radial-velocity data obtained with the high-resolution spectrometers ARCES, of the 3.5 m ARC telescope at Apache Point observatory, and SOPHIE, of the 1.93 m telescope at Haute-Provence Observatory. The "dynamical"mass of the RG component was determined with a 2% precision at 1.30-0.02+0.03 M. We performed asteroseismic modeling based on the global seismic parameters and on the individual frequencies. Both methods provide an estimate of the mass of the RG that matches the dynamical mass within the uncertainties. Asteroseismology also revealed the rotation rate of the core (≈15 days), the envelope (~150 days), and the inclination (~75º) of the RG. Three different approaches led to an estimation of the age between 3.3 and 5.8 Gyr, which highlights the difficulty of determining stellar ages despite the exceptional wealth of information available for this system. On short timescales, the inner binary exhibits eclipses with varying depths during a 7.3-year long interval, and no eclipses during the consecutive 11.9 years. This is why Kepler could detect its eclipses but TESS cannot, and the future ESA PLATO mission should detect these. In the long term, the system appears to be stable and owes its evolution to the evolution of its individual components. This triple system could end its current smooth evolution by merging by the end of the RGB of the primary star because the periastron distance is ≈142 R, which is close to the expected radius of the RG at the tip of the RGB.

Original languageEnglish
Article numberA173
Number of pages26
JournalAstronomy and Astrophysics
Volume668
DOIs
Publication statusPublished - 19 Dec 2022

Bibliographical note

Funding Information:
This paper includes data collected by the Kepler mission. Funding for the Kepler mission is provided by the NASA Science Mission directorate. Some of the data presented in this paper were obtained from the Mikulski Archive for Space Telescopes (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. This work is also based on observations obtained with the Apache Point Observatory 3.5-m telescope, which is owned and operated by the Astrophysical Research Consortium. Part of our spectroscopic observations were done at the Observatoire de Haute-Provence. We acknowledge the technical team for their onsite support as well as the “Programme National de Physique Stellaire” (PNPS) of CNRS/INSU for their financial support. P.G. and F.S. were supported by the German space agency (Deutsches Zentrum für Luft- und Raumfahrt) under PLATO data grant 50OO1501. P.G. and J.J. acknowledge NASA grant NNX17AF74G for partial support. The research leading to these results has (partially) received funding from the KU Leuven Research Council (grant C16/18/005: PARADISE) and from the Belgian federal Science Policy Office (BELSPO) through PRODEX grant PLATO. M.B. acknowledges support from the “Deutscher Akademischer Austauschdienst” (DAAD) and the Université Paris Diderot.

Keywords

  • Binaries: close
  • Binaries: spectroscopic
  • Stars: evolution
  • Stars: oscillations
  • Techniques: photometric
  • Techniques: radial velocities

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Fingerprint

Dive into the research topics of 'KIC 7955301: A hierarchical triple system with eclipse timing variations and an oscillating red giant'. Together they form a unique fingerprint.

Cite this