一颗可能围绕振荡的K巨星α Arietis运行的系外行星
A likely exoplanet orbiting the oscillating K-giant α Arietis
摘要：
目标。为了寻找中等质量恒星周围的太阳系外行星，我们正在K巨星周围进行精确的RV调查。方法.我们提供了从2003年11月到2010年2月对α Ari进行的高精度RV测量。这颗恒星属于我们的55颗K巨星样本，这些样本是使用连接在韩国宝贤山光学天文台（BOAO）1.8米望远镜上的光纤馈入宝贤山天文台Echelle光谱仪（BOES）进行太阳系外行星和脉动搜索研究的。结果我们在振荡的K2 III型恒星α Ari（HD 12929）中发现了一个具有长周期和低振幅径向速度（RV）变化的行星伴星。我们没有发现RV变化与色球活动指标（Ca Ⅱ H & K区，Hα线）之间的相关性。平分线分析还表明，平分线速度跨度（BVS）没有表现出任何明显的相关性与RV的变化，但有周期性的成分，可能是由于恒星的旋转。如果RV的变化确实是由行星伴星引起的，那么周期P = 381天、半振幅K = 41 m/s、离心率e = 0.25的轨道解最符合数据。假设可能的恒星质量为M_star = 1.5 M_sun，我们估计了轨道半长轴为1.2 AU的m2 sin i = 1.8 M_Jupiter的行星伴星的最小质量。结论.我们在α Ari中发现了一颗可能的系外行星，这支持了在具有多周期振荡的巨恒星周围寻找太阳系外行星。
英文摘要：
Aims. To search for extrasolar planets around intermediate-mass stars, we are conducting a precise RV survey around K-giants. Methods. We present high-accuracy RV measurements of α Ari made from November 2003 to February 2010. This star belongs to our sample of 55 K-giants studied for extrasolar planet and pulsation searches using the fiber-fed Bohyunsan Observatory Echelle Spectrograph (BOES) attached to the 1.8-m telescope at Bohyunsan Optical Astronomy Observatory (BOAO) in Korea. Results. We find a planetary companion with long-period and low-amplitude radial velocity (RV) variations in oscillating K2 III star α Ari (HD 12929). We do not find the correlation between RV variations and chromospheric activity indicators (Ca II H & K region, Hα line). The bisector analysis also shows that the bisector velocity span (BVS) does not show any obvious correlation with RV variation but has periodic component that may be attributed to the rotation of the star. If the RV variation is indeed caused by a planetary companion, an orbital solution with a period of P = 381 days, a semi-amplitude of K = 41 m/s, and an eccentricity of e = 0.25 fits the data best. Assuming a possible stellar mass of M_star = 1.5 M_sun, we estimate the minimum mass for the planetary companion of m2 sin i = 1.8 M_Jupiter with an orbital semi-major axis of 1.2 AU. Conclusions. Our finding of a likely exoplanet in α Ari supports searching for extrasolar planets around giant stars with multiperiodic oscillations.
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