太阳附近单个晚型巨星的磁场：巨星分支上的磁活动有多普遍？
Magnetic fields in single late-type giants in the Solar vicinity: How common is magnetic activity on the giant branches?
摘要：
我们提出了我们的第一个结果，在一个新的样本，包含所有单一的G，K和M巨星下降到V = 4等在太阳附近，适合光谱偏振（斯托克斯V）的观察Narval在TBL，法国。对于磁场（MF）的探测和测量，应用了最小二乘反卷积（LSD）方法（Donati等人，1997），在目前的情况下，该方法能够探测甚至比太阳磁场更弱的大规模MF（我们纵向MF测量的典型精度为0.1-0.2 G）。恒星的演化状态是基于旋转的演化模型确定的（Lagarde et al. 2012; Charbonnel et al.，（正在编写中）和Massarotti等人（1998）给出的基本参数。这些恒星的质量范围在1-4太阳质量之间，处于主序星（MS）之后到渐近巨星分支（AGB）的不同演化阶段。该样本包含45颗恒星。到目前为止，观测到29颗恒星（即约占样本的64%），每颗至少观测两次。对于在赫兹普龙间隙中的两颗恒星，其中一颗肯定是塞曼探测到的。只有5个G和K巨星，主要位于红巨星分支（RGB）的底部和He燃烧阶段。令人惊讶的是，许多恒星上升到RGB尖端，并在早期AGB阶段被检测到（13个观察到的恒星中的8个）。对于所有塞曼探测到的恒星，vsin i都被重新确定，出现在2-3 km/s的区间，但很少有具有MF的巨星具有更大的vsin i。
英文摘要：
We present our first results on a new sample containing all single G,K and M giants down to V = 4 mag in the Solar vicinity, suitable for spectropolarimetric (Stokes V) observations with Narval at TBL, France. For detection and measurement of the magnetic field (MF), the Least Squares Deconvolution (LSD) method was applied (Donati et al. 1997) that in the present case enables detection of large-scale MFs even weaker than the solar one (the typical precision of our longitudinal MF measurements is 0.1-0.2 G). The evolutionary status of the stars is determined on the basis of the evolutionary models with rotation (Lagarde et al. 2012; Charbonnel et al., in prep.) and fundamental parameters given by Massarotti et al. (1998). The stars appear to be in the mass range 1-4 M_sun, situated at different evolutionary stages after the Main Sequence (MS), up to the Asymptotic Giant Branch (AGB). The sample contains 45 stars. Up to now, 29 stars are observed (that is about 64 % of the sample), each observed at least twice. For 2 stars in the Hertzsprung gap, one is definitely Zeeman detected. Only 5 G and K giants, situated mainly at the base of the Red Giant Branch (RGB) and in the He-burning phase are detected. Surprisingly, a lot of stars ascending towards the RGB tip and in early AGB phase are detected (8 of 13 observed stars). For all Zeeman detected stars v sin i is redetermined and appears in the interval 2-3 km/s, but few giants with MF possess larger v sin i.
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