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LONG-PERIOD VARIATIONS IN THE RADIAL VELOCITY OF SPECTROSCOPIC BINARY M GIANT μ URSAE MAJORIS

2016; Institute of Physics; Volume: 151; Issue: 4 Linguagem: Inglês

10.3847/0004-6256/151/4/106

1538-3881

Byeong‐Cheol Lee, Inwoo Han, Myeong‐Gu Park, D. E. Mkrtichian, A. P. Hatzes, Gwanghui Jeong, Kang-Min Kim,

Astrophysical Phenomena and Observations

We report that the spectroscopic binary ? Ursae Majoris (?mu UMa) has secondary RV variations of 471.2 days in addition to those of 230.0 days already known. Keplerian orbit analysis yields stellar mass companions of 1.6 M_Sun for the 230-d period and 0.14 M_Sun for the 471-d period. However, the HIPPARCOS photometries show a period similar to the stellar rotational period, which is one-quarter of the RV period. Variations in the bisector velocity curvature show a period of 463.6 days. We also find ~?473-day variations in the equivalent width (EW) measurements of the H_alpha and H_beta lines, whose origin is probably stellar activity. We note that the nature of 471-day variations is similar to one observed in "Sequence D" of symptotic Giant Branch (AGB) pulsating stars. We therefore conclude that the RV and the EW variations in the spectroscopic binary M giant mu UMa A originate from the complex pulsations and the chromospheric activity.