KIC 5950759: a high-amplitude δ Sct star with amplitude and frequency modulation near the terminal age main sequence

Bowman, D. M. and Hermans, J. and Daszynska-Daszkiewicz, J. and Holdsworth, D. L. and Tkachenko, A. and Murphy, S. J. and Smalley, B. and Kurtz, D. W. (2021) KIC 5950759: a high-amplitude δ Sct star with amplitude and frequency modulation near the terminal age main sequence. Monthly Notices of the Royal Astronomical Society, 504 (3). pp. 4039-4053. ISSN 0035-8711

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Abstract

Among the intermediate mass pulsating stars known as δ Sct stars is a subset of high-amplitude and predominantly radial-mode pulsators known as high-amplitude δ Sct (HADS) stars. From more than 2000 δ Sct stars observed by the Kepler space mission, only two HADS stars were detected. We investigate the more perplexing of these two HADS stars, KIC 5950759. We study its variability using ground- and space-based photometry, determine its atmospheric parameters from spectroscopy and perform asteroseismic modelling to constrain its mass and evolutionary stage. From spectroscopy, we find that KIC 5950759 is a metal-poor star, which is in agreement with the inferred metallicity needed to reproduce its pulsation mode frequencies from non-adiabatic pulsation models. Furthermore, we combine ground-based WASP and Kepler space photometry, and measure a linear change in period of order P˙/P≃10−6 yr−1 for both the fundamental and first overtone radial modes across a time base of several years, which is at least two orders of magnitude larger than predicted by evolution models, and is the largest measured period change in a δ Sct star to date. Our analysis indicates that KIC 5950759 is a metal-poor HADS star near the short-lived contraction phase and the terminal-age main sequence, with its sub-solar metallicity making it a candidate SX Phe star. KIC 5950759 is a unique object among the thousands of known δ Sct stars and warrants further study to ascertain why its pulsation modes are evolving remarkably faster than predicted by stellar evolution.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Faculty/School / Institute/Centre: No Faculty
Faculty/School / Institute/Centre: No Faculty
Date Deposited: 13 Jul 2022 05:46
Last Modified: 13 Jul 2022 23:49
Uncontrolled Keywords: asteroseismology; stars: individual: KIC 5950759; 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/stab1124
URI: http://eprints.usq.edu.au/id/eprint/47866

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