Can circumbinary discs produce the eccentricities of shell-burning stripped giant binaries?
- 1Department of Astrophysics/IMAPP, Radboud University Nijmegen
- 2Institute of Astronomy, KU Leuven, Celestijnenlaan 200D
Abstract
Context. Post-red giant branch and post-asymptotic giant branch binaries, collectively known as shell-burning stripped giant (SBSG) binaries, contain a primary star that has recently been stripped of its envelope, alongside a main-sequence companion. These systems are characterised by a stable circumbinary disc (CBD), which is thought to have formed from the envelope material stripped via mass transfer. Their eccentricities range between 0 − 0.63, contradicting canonical binary evolution, which predicts that such post-mass-transfer systems ought to have circularised. Aims. We investigate whether interaction between a binary and its CBD can explain the observed eccentricities of SBSG binaries. Methods. We utilised a new formalism for CBD-binary interaction based on hydrodynamic simulations. To perform a comparison with the observations, we generated model populations for which the post-mass-transfer eccentricity and the amount of material accreted from the CBD were free parameters. Results. We found that CBD-binary interaction can reproduce the observed eccentricity distribution of SBSG binaries, provided that: (1) their post-mass-transfer eccentricities range up to at least 0.05; (2) their CBDs have initial masses of at least 0.1 M⊙; and (3) accretion onto the SBSG star is highly inefficient, preventing the refilling of its Roche lobe. Conclusions. Our model requires higher post-mass-transfer eccentricities than are canonically predicted and more massive CBDs than are currently observed. We speculate that there is a population of post-mass-transfer progenitor systems with CBDs massive enough to facilitate significant eccentricity pumping. Mass loss via the L2 point during mass transfer needs to be investigated, as this could form the CBD and shorten the orbital period, which would be necessary for many SBSG binaries assuming they formed stably. We hypothesise that the observed eccentricities are related to the amount of mass lost via L2. Since many other post-interaction systems exhibit similar orbital properties, we speculate that they may all have interacted with CBDs shortly after mass transfer.
Versions
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BibTeX
@article{a2026circumbinary,
title = {{Can circumbinary discs produce the eccentricities of shell-burning stripped giant binaries?}},
author = {Moltzer C. A. S. and Pols O. R. and Van Winckel H.},
journal = {Astronomy \& Astrophysics},
year = {2026},
month = oct,
doi = {10.1051/0004-6361/202661541},
url = {https://doi.org/10.1051/0004-6361/202661541},
note = {CC BY},
}
RIS
TY - JOUR
TI - Can circumbinary discs produce the eccentricities of shell-burning stripped giant binaries?
AU - Moltzer C. A. S.
AU - Pols O. R.
AU - Van Winckel H.
PY - 2026
DA - 2026/10/23
JO - Astronomy & Astrophysics
DO - 10.1051/0004-6361/202661541
UR - https://doi.org/10.1051/0004-6361/202661541
AB - Context. Post-red giant branch and post-asymptotic giant branch binaries, collectively known as shell-burning stripped giant (SBSG) binaries, contain a primary star that has recently been stripped of its envelope, alongside a main-sequence companion. These systems are characterised by a stable circumbinary disc (CBD), which is thought to have formed from the envelope material stripped via mass transfer. Their eccentricities range between 0 − 0.63, contradicting canonical binary evolution, which predicts that such post-mass-transfer systems ought to have circularised. Aims. We investigate whether interaction between a binary and its CBD can explain the observed eccentricities of SBSG binaries. Methods. We utilised a new formalism for CBD-binary interaction based on hydrodynamic simulations. To perform a comparison with the observations, we generated model populations for which the post-mass-transfer eccentricity and the amount of material accreted from the CBD were free parameters. Results. We found that CBD-binary interaction can reproduce the observed eccentricity distribution of SBSG binaries, provided that: (1) their post-mass-transfer eccentricities range up to at least 0.05; (2) their CBDs have initial masses of at least 0.1 M⊙; and (3) accretion onto the SBSG star is highly inefficient, preventing the refilling of its Roche lobe. Conclusions. Our model requires higher post-mass-transfer eccentricities than are canonically predicted and more massive CBDs than are currently observed. We speculate that there is a population of post-mass-transfer progenitor systems with CBDs massive enough to facilitate significant eccentricity pumping. Mass loss via the L2 point during mass transfer needs to be investigated, as this could form the CBD and shorten the orbital period, which would be necessary for many SBSG binaries assuming they formed stably. We hypothesise that the observed eccentricities are related to the amount of mass lost via L2. Since many other post-interaction systems exhibit similar orbital properties, we speculate that they may all have interacted with CBDs shortly after mass transfer.
SN - 0004-6361
SN - 1432-0746
ER -