Leaning Sideways: VHS 1256-1257 b is a Super-Jupiter with a Uranus-like Obliquity
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arXiv
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| Natura: | Preprint |
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2024
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| author | Poon, Michael Bryan, Marta L. Rein, Hanno Morley, Caroline V. Mace, Gregory Zhou, Yifan Bowler, Brendan P. |
| author_facet | Poon, Michael Bryan, Marta L. Rein, Hanno Morley, Caroline V. Mace, Gregory Zhou, Yifan Bowler, Brendan P. |
| contents | We constrain the angular momentum architecture of VHS J125601.92-125723.9, a 140 $\pm$ 20 Myr old hierarchical triple system composed of a low-mass binary and a widely-separated planetary-mass companion VHS 1256 b. VHS 1256 b has been a prime target for multiple characterization efforts, revealing the highest measured substellar photometric variability to date and the presence of silicate clouds and disequilibrium chemistry. Here we add a key piece to the characterization of this super-Jupiter on a Tatooine-like orbit; we measure its spin-axis tilt relative to its orbit, i.e. the obliquity of VHS 1256 b. We accomplish this by combining three measurements. We find a projected rotation rate $v \sin{i_p} = 8.7 \pm 0.1 \,\mathrm{km~s^{-1}}$ for VHS 1256 b using near-IR high-resolution spectra from Gemini/IGRINS. Combining this with a published photometric rotation period indicates that the companion is viewed edge-on, with a line-of-sight spin axis inclination of $i_{\rm p} = 90^\circ \pm 18^\circ$. We refit available astrometry measurements to confirm an orbital inclination of $i_{\rm o} = 23 \substack{+10 \\ -13}^\circ$. Taken together, VHS 1256 b has a large planetary obliquity of $ψ= 90^\circ \pm 25^\circ$. In total, we have three measured angular momentum vectors for the system: the binary orbit normal, companion orbit normal, and companion spin axis. All three are misaligned with respect to each other. Although VHS 1256 b is tilted like Uranus, their origins are distinct. We rule out planet-like scenarios including collisions and spin-orbit resonances, and suggest that top-down formation via core/filament fragmentation is promising. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2410_02672 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Leaning Sideways: VHS 1256-1257 b is a Super-Jupiter with a Uranus-like Obliquity Poon, Michael Bryan, Marta L. Rein, Hanno Morley, Caroline V. Mace, Gregory Zhou, Yifan Bowler, Brendan P. Earth and Planetary Astrophysics Solar and Stellar Astrophysics We constrain the angular momentum architecture of VHS J125601.92-125723.9, a 140 $\pm$ 20 Myr old hierarchical triple system composed of a low-mass binary and a widely-separated planetary-mass companion VHS 1256 b. VHS 1256 b has been a prime target for multiple characterization efforts, revealing the highest measured substellar photometric variability to date and the presence of silicate clouds and disequilibrium chemistry. Here we add a key piece to the characterization of this super-Jupiter on a Tatooine-like orbit; we measure its spin-axis tilt relative to its orbit, i.e. the obliquity of VHS 1256 b. We accomplish this by combining three measurements. We find a projected rotation rate $v \sin{i_p} = 8.7 \pm 0.1 \,\mathrm{km~s^{-1}}$ for VHS 1256 b using near-IR high-resolution spectra from Gemini/IGRINS. Combining this with a published photometric rotation period indicates that the companion is viewed edge-on, with a line-of-sight spin axis inclination of $i_{\rm p} = 90^\circ \pm 18^\circ$. We refit available astrometry measurements to confirm an orbital inclination of $i_{\rm o} = 23 \substack{+10 \\ -13}^\circ$. Taken together, VHS 1256 b has a large planetary obliquity of $ψ= 90^\circ \pm 25^\circ$. In total, we have three measured angular momentum vectors for the system: the binary orbit normal, companion orbit normal, and companion spin axis. All three are misaligned with respect to each other. Although VHS 1256 b is tilted like Uranus, their origins are distinct. We rule out planet-like scenarios including collisions and spin-orbit resonances, and suggest that top-down formation via core/filament fragmentation is promising. |
| title | Leaning Sideways: VHS 1256-1257 b is a Super-Jupiter with a Uranus-like Obliquity |
| topic | Earth and Planetary Astrophysics Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2410.02672 |