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标题：The Warm Neptunes around HD 106315 Have Low Stellar Obliquities
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作者：George Zhou ; Joseph E. Rodriguez ; Andrew Vanderburg 等
期刊名称：The Astronomical journal
印刷版ISSN：0004-6256
电子版ISSN：1538-3881
出版年度：2018
卷号：156
期号：3
页码：1-10
DOI：10.3847/1538-3881/aad085
语种：English
出版社：American Institute of Physics
摘要：We present the obliquity of the warm Neptune HD 106315c measured via a series of spectroscopic transitobservations. HD 106315c is a 4.4 R Earth warm Neptune orbiting a moderately rotating late F star with a period of21.05 days. HD 106315 also hosts a 2.5 R Earth super-Earth on a 9.55 day orbit. Our Doppler tomographic analysesof four transits observed by the Magellan/MIKE, HARPS, and TRES facilities find HD 106315c to be in a lowstellar obliquity orbit, consistent with being well aligned with the spin axis of the host star at 10.9 3.8 3.6 l = - -+ . Wesuggest, via dynamical N-body simulations, that the two planets in the system must be coplanar, and thus are bothwell aligned with the host star. HD 106315 is only the fourth warm Neptune system with obliquities measured. Allwarm Neptune systems have been found in well aligned geometries, consistent with the interpretation that thesesystems are formed in situ in the inner protoplanetary disk, and also consistent with the majority of Kepler multi-planet systems that are in low obliquity orbits. With a transit depth of 1.02 mmag, HD 106315c is among thesmallest planets to have been detected in transit spectroscopy, and we discuss its detection in the context of TESSand the next generations of spectrographs.
关键词：planets and satellites: dynamical evolution and stability;planets and satellites: individual (HD 106315)