Report
An extremely low-density exoplanet spins slow
| العنوان: | An extremely low-density exoplanet spins slow |
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| المؤلفون: | Liu, Quanyi, Zhu, Wei, Masuda, Kento, Libby-Roberts, Jessica E., Bello-Arufe, Aaron, Canas, Caleb I. |
| سنة النشر: | 2024 |
| المجموعة: | Astrophysics |
| مصطلحات موضوعية: | Astrophysics - Earth and Planetary Astrophysics |
| الوصف: | We present constraints on the shape of Kepler-51d, which is a super-puff with a mass $\sim6\,M_\oplus$ and a radius $\sim9\,R_\oplus$, based on detailed modeling of the transit light curve from JWST NIRSpec. The projected shape of this extremely low-density planet is consistent with being spherical, and a projected oblateness $f_\perp>0.2$ can be excluded regardless of the spin obliquity angles. If this is taken as the limit on the true shape of the planet, Kepler-51d is rotating at $\lesssim 50\%$ of its break-up spin rate, or its rotation period is $\gtrsim 33\,$hr. In the more plausible situation that the planetary spin is aligned with its orbital direction to within $30^\circ$, then its oblateness is $<0.08$, which corresponds to a dimensionless spin rate $\lesssim30\%$ of the break-up rotation and a dimensional rotation period $\gtrsim 53\,$hr. This seems to contradict the theoretical expectation that planets with such low masses may be spinning near break-up. We point out the usefulness of the stellar mean density and the orbital eccentricity in constraining the shape of the transiting planet, so planets with well-characterized host and orbital parameters are preferred in the detection of planetary oblateness with the JWST transit method. Comment: 11 pages, 4 figures. Accepted by ApJL |
| نوع الوثيقة: | Working Paper |
| DOI: | 10.3847/2041-8213/ad8f39 |
| URL الوصول: | http://arxiv.org/abs/2410.07977 |
| رقم الانضمام: | edsarx.2410.07977 |
| قاعدة البيانات: | arXiv |
| DOI: | 10.3847/2041-8213/ad8f39 |
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