A binary with a δ Scuti star and an oscillating red giant: orbit and asteroseismology of KIC 9773821

Murphy, Simon J. and Li, Tanda and Sekaran, Sanjay and Bedding, Timothy R. and Yu, Jie and Tkachenko, Andrew and Colman, Isabel and Huber, Daniel and Hey, Daniel and Baratashvili, Tinatin and Janssens, Soetkin (2021) A binary with a δ Scuti star and an oscillating red giant: orbit and asteroseismology of KIC 9773821. Monthly Notices of the Royal Astronomical Society, 505 (2). pp. 2336-2348. ISSN 0035-8711

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Abstract

We study the δScuti - red giant (RG) binary KIC 9773821, the first double-pulsator binary of its kind. It was observed by Kepler during its 4-yr mission. Our aims are to ascertain whether the system is bound, rather than a chance alignment, and to identify the evolutionary state of the RG via asteroseismology. An extension of these aims is to determine a dynamical mass and an age prior for a δSct star, which may permit mode identification via further asteroseismic modelling. We determine spectroscopic parameters and radial velocities (RVs) for the RG component using HERMES@Mercator spectroscopy. Light arrival-time delays from the δSct pulsations are used with the red-giant RVs to determine that the system is bound and to infer its orbital parameters, including the binary mass ratio. We use asteroseismology to model the individual frequencies of the red giant to give a mass of $2.10^{+0.20}_{-0.10}$ M⊙ and an age of $1.08^{+0.06}_{-0.24}$ Gyr. We find that it is a helium-burning secondary clump star, confirm that it follows the standard $\nu _{\rm max}$ scaling relation, and confirm its observed period spacings match their theoretical counterparts in the modelling code mesa. Our results also constrain the mass and age of the δSct star. We leverage these constraints to construct δSct models in a reduced parameter space and identify four of its five pulsation modes.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: File reproduced in accordance with the copyright policy of the publisher/author.
Faculty/School / Institute/Centre: No Faculty
Faculty/School / Institute/Centre: No Faculty
Date Deposited: 10 Jul 2022 22:35
Last Modified: 11 Jul 2022 03:06
Uncontrolled Keywords: asteroseismology, binaries: spectroscopic, stars: oscillations, stars: variables: δ Scuti, Astrophysics - Solar and Stellar Astrophysics
Fields of Research (2020): 51 PHYSICAL SCIENCES > 5101 Astronomical sciences > 510109 Stellar astronomy and planetary systems
Socio-Economic Objectives (2020): 28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280120 Expanding knowledge in the physical sciences
Identification Number or DOI: https://doi.org/10.1093/mnras/stab1436
URI: http://eprints.usq.edu.au/id/eprint/47925

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