Issue |
A&A
Volume 650, June 2021
|
|
---|---|---|
Article Number | A178 | |
Number of page(s) | 10 | |
Section | Celestial mechanics and astrometry | |
DOI | https://doi.org/10.1051/0004-6361/202038940 | |
Published online | 24 June 2021 |
Orbital evolution of potentially habitable planets of tidally interacting binary stars
1
Institut für Theoretische Astrophysik (ITA), Zentrum für Astronomie (ZAH), Universität Heidelberg,
Albert-Ueberle-Str. 2,
69120
Heidelberg, Germany
e-mail: dglezg7@hotmail.com
2
Astronomy Department, University of Washington,
Box 951580,
Seattle,
WA
98195, USA
3
NASA Virtual Planetary Laboratory,
Seattle,
WA
98195, USA
Received:
15
July
2020
Accepted:
2
November
2020
We simulate the coupled stellar and tidal evolution of short-period binary stars (orbital period Porb ≲ 8 days) to investigate the orbital oscillations, instellation cycles, and orbital stability of circumbinary planets (CBPs). We consider two tidal models and show that both predict an outward-then-inward evolution of the binary’s semi-major axis abin and eccentricity ebin. This orbital evolution drives a similar evolution of the minimum CBP semi-major axis for orbital stability. By expanding on previous models to include the evolution of the mass concentration, we show that the maximum in the CBP orbital stability limit tends to occur 100 Myr after the planets form, a factor of 100 longer than previous investigations. This result provides further support for the hypothesis that the early stellar-tidal evolution of binary stars has removed CBPs from short-period binaries. We then apply the models to Kepler-47 b, a CBP orbiting close to its host stars’ stability limit, to show that if the binary’s initial ebin ≳ 0.24, the planet would have been orbiting within the instability zone in the past and probably wouldn’t have survived. For stable, hypothetical cases in which the stability limit does not reach a planet’s orbit, we find that the amplitudes of abin and ebin oscillations can damp by up to 10% and 50%, respectively. Finally, we consider equal-mass stars with Porb = 7.5 days and compare the HZ to the stability limit. We find that for stellar masses ≲0.12 M⊙, the HZ is completely unstable, even if the binary orbit is circular. For ebin ≲ 0.5, that limit increases to 0.17 M⊙, and the HZ is partially destabilized for stellar masses up to 0.45 M⊙. These results may help guide searches for potentially habitable CBPs, as well as characterize their evolution and likelihood to support life after they are found.
Key words: astrobiology / planets and satellites: dynamical evolution and stability / binaries (including multiple): close / stars: low-mass / planet-star interactions
© D. E. Graham et al. 2021
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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