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标题：Evidence for at least three planet candidates orbiting HD 20794
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作者：F. Feng ; F. Feng ; M. Tuomi 等
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2017
卷号：605
页码：1-11
DOI：10.1051/0004-6361/201730406
语种：English
出版社：EDP Sciences
摘要：Aims. We explore the feasibility of detecting Earth analogs around Sun-like stars using the radial velocity method by investigating one of the largest radial velocities data sets for the one of the most stable radial-velocity stars HD 20794. Methods. We proceed by disentangling the Keplerian signals from correlated noise and activity-induced variability. We diagnose the noise using the differences between radial velocities measured at different wavelength ranges, so-called “differential radial velocities”. Results. We apply this method to the radial velocities measured by HARPS, and identify four signals at 18, 89, 147 and 330 d. The two signals at periods of 18 and 89 d are previously reported and are better quantified in this work. The signal at a period of about 147 d is reported for the first time, and corresponds to a super-Earth with a minimum mass of 4.59 Earth mass located 0.51 AU from HD 20794. We also find a significant signal at a period of about 330 d corresponding to a super-Earth or Neptune in the habitable zone. Since this signal is close to the annual sampling period and significant periodogram power in some noise proxies are found close to this signal, further observations and analyses are required to confirm it. The analyses of the eccentricity and consistency of signals provide weak evidence for the existence of the previously reported 43 d signal and a new signal at a period of about 11.9 d with a semi-amplitude of 0.4 m/s. Conclusions. We find that the detection of a number of signals with radial velocity variations around 0.5 m/s that are likely caused by low mass planet candidates demonstrates the important role of noise modeling in searching for Earth analogs.
关键词：enmethods: statisticalmethods: numericaltechniques: radial velocitiesstars: individual: HD 20794