Reduction of the maximum mass-loss rate of OH/IR stars due to unnoticed binary interaction

Decin, L.; Homan, W.; Danilovich, T.; de Koter, A.; Engels, D.; Waters, L. B. F. M.; Muller, S.; Gielen, C.; García-Hernández, D. A.; Stancliffe, R. J.; Van de Sande, M.; Molenberghs, G.; Kerschbaum, F.; Zijlstra, A. A.; El Mellah, I.
Bibliographical reference

Nature Astronomy, Volume 3, p. 408-415

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2
2019
Number of authors
15
IAC number of authors
1
Citations
25
Refereed citations
22
Description
In 1981, the idea of a superwind that ends the life of cool giant stars was proposed1. Extreme oxygen-rich giants, OH/IR stars, develop superwinds with the highest mass-loss rates known so far, up to a few 10-4 solar masses (M⊙) per year2-12, informing our understanding of the maximum mass-loss rate achieved during the asymptotic giant branch (AGB) phase. A conundrum arises whereby the observationally determined duration of the superwind phase is too short for these stars to lose enough mass to become white dwarfs2-4,6,8-10. Here we report on the detection of spiral structures around two cornerstone extreme OH/IR stars, OH 26.5 + 0.6 and OH 30.1 - 0.7, thereby identifying them as wide binary systems. Hydrodynamic simulations show that the companion's gravitational attraction creates an equatorial density enhancement mimicking a short, extreme superwind phase, thereby solving the decades-old conundrum. This discovery restricts the maximum mass-loss rate of AGB stars to around the single-scattering radiation pressure limit of a few 10-5 M⊙ yr-1. This has crucial implications for nucleosynthetic yields, planet survival and the wind-driving mechanism.
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Nucleosynthesis and molecular processes in the late stages of Stellar Evolution
Low- to intermediate-mass (M < 8 solar masses, Ms) stars represent the majority of stars in the Cosmos. They finish their lives on the Asymptotic Giant Branch (AGB) - just before they form planetary nebulae (PNe) - where they experience complex nucleosynthetic and molecular processes. AGB stars are important contributors to the enrichment of the
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García Hernández