Polar alignment of a circumbinary disc around a brown dwarf binary
Fuente:
arXiv
Saved in:
| Main Authors: | , , , |
|---|---|
| Format: | Preprint |
| Published: |
2025
|
| Subjects: | |
| Online Access: | |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1866915363905601536 |
|---|---|
| author | Smallwood, Jeremy L. Baycroft, Thomas A. Triaud, Amaury H. M. J. Nelson, Richard P. |
| author_facet | Smallwood, Jeremy L. Baycroft, Thomas A. Triaud, Amaury H. M. J. Nelson, Richard P. |
| contents | Inspired by recent observations suggesting that the retrograde precession of the brown dwarf binary 2M1510 AB is consistent with induction by a polar circumbinary planet, we investigate the formation of such planets by studying the evolution of a primordial misaligned circumbinary disc around a brown dwarf binary. Analytical calculations show that a critical tilt angle of $i_{\rm crit} \gtrsim 50^\circ$ for moderately eccentric binaries is needed for polar alignment of circumbinary discs in systems with low disc-to-binary angular momentum ratios. For higher ratios, this angle converges to the Kozai-Lidov instability threshold of $\sim 39^\circ$. We identify disc parameters, such as viscosity ($α= 10^{-4}$) and aspect ratio ($H/r = 0.05$), that enable polar alignment within typical disc lifetimes. Notably, a circumbinary disc around a low-mass binary, such as a brown dwarf binary, will require more time to achieve polar alignment compared to higher-mass systems. A hydrodynamical simulation confirms that an initially inclined disc around a brown dwarf evolves towards a polar state, creating favorable conditions for polar planet formation. Using these results, we finish by placing 2M1510 AB into a wider context and speculate why such a polar circumbinary configuration has not been identified before. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2506_22747 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Polar alignment of a circumbinary disc around a brown dwarf binary Smallwood, Jeremy L. Baycroft, Thomas A. Triaud, Amaury H. M. J. Nelson, Richard P. Earth and Planetary Astrophysics Solar and Stellar Astrophysics Inspired by recent observations suggesting that the retrograde precession of the brown dwarf binary 2M1510 AB is consistent with induction by a polar circumbinary planet, we investigate the formation of such planets by studying the evolution of a primordial misaligned circumbinary disc around a brown dwarf binary. Analytical calculations show that a critical tilt angle of $i_{\rm crit} \gtrsim 50^\circ$ for moderately eccentric binaries is needed for polar alignment of circumbinary discs in systems with low disc-to-binary angular momentum ratios. For higher ratios, this angle converges to the Kozai-Lidov instability threshold of $\sim 39^\circ$. We identify disc parameters, such as viscosity ($α= 10^{-4}$) and aspect ratio ($H/r = 0.05$), that enable polar alignment within typical disc lifetimes. Notably, a circumbinary disc around a low-mass binary, such as a brown dwarf binary, will require more time to achieve polar alignment compared to higher-mass systems. A hydrodynamical simulation confirms that an initially inclined disc around a brown dwarf evolves towards a polar state, creating favorable conditions for polar planet formation. Using these results, we finish by placing 2M1510 AB into a wider context and speculate why such a polar circumbinary configuration has not been identified before. |
| title | Polar alignment of a circumbinary disc around a brown dwarf binary |
| topic | Earth and Planetary Astrophysics Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2506.22747 |