| Autor: |
Ryan A. Rubenzahl, Fei Dai, Samuel Halverson, Andrew W. Howard, Aaron Householder, Benjamin Fulton, Aida Behmard, Steven R. Gibson, Arpita Roy, Abby P. Shaum, Howard Isaacson, Max Brodheim, William Deich, Grant M. Hill, Bradford Holden, Russ R. Laher, Kyle Lanclos, Joel N. Payne, Erik A. Petigura, Christian Schwab, Chris Smith, Guðmundur Stefánsson, Josh Walawender, Sharon X. Wang, Lauren M. Weiss, Joshua N. Winn, Edward Wishnow |
| Jazyk: |
angličtina |
| Rok vydání: |
2024 |
| Předmět: |
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| Zdroj: |
The Astronomical Journal, Vol 168, Iss 5, p 188 (2024) |
| Druh dokumentu: |
article |
| ISSN: |
1538-3881 |
| DOI: |
10.3847/1538-3881/ad70b5 |
| Popis: |
We present the first spectroscopic transit results from the newly commissioned Keck Planet Finder on the Keck-I telescope at W. M. Keck Observatory. We observed a transit of KELT-18 b, an inflated ultrahot Jupiter orbiting a hot star ( T _eff = 6670 K) with a binary stellar companion. By modeling the perturbation to the measured cross-correlation functions using the Reloaded Rossiter–McLaughlin technique, we derived a sky-projected obliquity of λ = − 94.°8 ± 0.°7 ( $\psi ={93.8}_{-1.8}^{+1.6}\circ $ for isotropic i _⋆ ). The data are consistent with an extreme stellar differential rotation ( α = 0.9), though a more likely explanation is moderate center-to-limb variations of the emergent stellar spectrum. We see additional evidence for the latter from line widths increasing toward the limb. Using loose constraints on the stellar rotation period from observed variability in the available TESS photometry, we were able to constrain the stellar inclination and thus the true 3D stellar obliquity to $\psi ={91.7}_{-1.8}^{+2.2}\circ $ . KELT-18 b could have obtained its polar orbit through high-eccentricity migration initiated by Kozai–Lidov oscillations induced by the binary stellar companion KELT-18 B, as the two likely have a large mutual inclination as evidenced by Gaia astrometry. KELT-18 b adds another data point to the growing population of close-in polar planets, particularly around hot stars. |
| Databáze: |
Directory of Open Access Journals |
| Externí odkaz: |
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