The Oblique Orbit of WASP-107b from K2 Photometry
Observations of nine transits of WASP-107 during the K2 mission reveal three separate occasions when the planet crossed in front of a starspot. The data confirm the stellar rotation period to be 17 days-approximately three times the planet's orbital period-and suggest that large spots persist f...
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Published in | The Astronomical journal Vol. 153; no. 5; pp. 205 - 211 |
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Main Authors | , |
Format | Journal Article |
Language | English |
Published |
United States
The American Astronomical Society
01.05.2017
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Subjects | |
Online Access | Get full text |
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Summary: | Observations of nine transits of WASP-107 during the K2 mission reveal three separate occasions when the planet crossed in front of a starspot. The data confirm the stellar rotation period to be 17 days-approximately three times the planet's orbital period-and suggest that large spots persist for at least one full rotation. If the star had a low obliquity, at least two additional spot crossings should have been observed. They were not observed, giving evidence for a high obliquity. We use a simple geometric model to show that the obliquity is likely in the range 40°-140°, i.e., both spin-orbit alignment and anti-alignment can be ruled out. WASP-107 thereby joins the small collection of relatively low-mass stars with a high obliquity. Most such stars have been observed to have low obliquities; all of the exceptions, including WASP-107, involve planets with relatively wide orbits ("warm Jupiters," with ). This demonstrates a connection between stellar obliquity and planet properties, in contradiction to some theories for obliquity excitation. |
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Bibliography: | The Solar System, Exoplanets, and Astrobiology AAS04442 |
ISSN: | 0004-6256 1538-3881 1538-3881 |
DOI: | 10.3847/1538-3881/aa65d1 |