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)
