تقرير
Orbital properties of binary post-AGB stars
| العنوان: | Orbital properties of binary post-AGB stars |
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| المؤلفون: | Oomen, Glenn-Michael, Van Winckel, Hans, Pols, Onno, Nelemans, Gijs, Escorza, Ana, Manick, Rajeev, Kamath, Devika, Waelkens, Christoffel |
| المصدر: | A&A 620, A85 (2018) |
| سنة النشر: | 2018 |
| المجموعة: | Astrophysics |
| مصطلحات موضوعية: | Astrophysics - Solar and Stellar Astrophysics |
| الوصف: | Binary post-asymptotic giant branch (post-AGB) stars are thought to be the products of a strong but poorly-understood interaction during the AGB phase. The aim of this contribution is to update the orbital elements of a sample of galactic post-AGB binaries observed in a long-term radial-velocity monitoring campaign. Radial velocities are computed from high signal-to-noise spectra by use of a cross-correlation method. The radial-velocity curves are fitted by using both a least-squares algorithm and a Nelder-Mead simplex algorithm. We use a Monte Carlo method to compute uncertainties on the orbital elements. The resulting mass functions are used to derive a companion mass distribution by optimising the predicted to the observed cumulative mass-function distributions, after correcting for observational bias. As a result, we derive and update orbital elements for 33 galactic post-AGB binaries, among which 3 are new orbits. The orbital periods of the systems range from 100 to about 3000 days. Over 70 percent (23 out of 33) of our binaries have significant non-zero eccentricities ranging over all periods. Their orbits are non-circular despite the fact that the Roche-lobe radii are smaller than the maximum size of a typical AGB star and tidal circularisation should have been strong when the objects were on the AGB. We derive a distribution of companion masses that is peaked around 1.09 $M_\odot$ with a standard deviation of 0.62 $M_\odot$. The large spread in companion masses highlights the diversity of post-AGB binary systems. Furthermore, we find that only post-AGB stars with high effective temperatures (> 5500 K) in wide orbits are depleted in refractory elements, suggesting that re-accretion of material from a circumbinary disc is an ongoing process. It appears, however, that chemical depletion is inefficient for the closest orbits irrespective of the actual surface temperature. Comment: 21 pages total, 3 appendices, 8 figures excluding appendix figures, 3 tables |
| نوع الوثيقة: | Working Paper |
| DOI: | 10.1051/0004-6361/201833816 |
| URL الوصول: | http://arxiv.org/abs/1810.01842 |
| رقم الأكسشن: | edsarx.1810.01842 |
| قاعدة البيانات: | arXiv |
| DOI: | 10.1051/0004-6361/201833816 |
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