A nine-season spectroscopic study of the photosphere of β Gem (K0 III) shows this low-luminosity giant to be stable, with no effective temperature variations above ~2?K, and no secular temperature variations over the 2002-2010 time span above 0.2?K per year. The radial-velocity variations are consistent with an orbital variation of ~40?m?s–1. The projected rotation rate is found to be 1.70?± 0.20?km?s–1 with a macroturbulence dispersion of 4.53?± 0.10?km?s–1. The third-signature plot is also invariant and shows a granulation velocity gradient 20% smaller than the solar gradient. The absolute shift of the third-signature plot gives a blueshift-corrected radial velocity of 3385?± 70?m?s–1. Bisector mapping of the Fe I λ6253 line yields a flux deficit of 12%?± 1% in area, somewhat smaller than for other giants, but the shape and the position of the peak at 4.8?km?s–1 is consistent with other giants. All of the investigated photospheric parameters are consistent with β Gem being a low-luminosity giant in agreement with its absolute magnitude.
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机译：对β宝石（K0 III）的光球进行了九个季节的光谱研究，表明该低发光度巨星是稳定的，在〜2？K以上没有有效的温度变化，并且在2002-2010年以上的时间跨度内没有长期温度变化每年0.2？K。径向速度变化与〜40？m？s–1的轨道变化一致。预计旋转速度为1.70？±0.20？km？s-1，宏观湍流散度为4.53？±0.10？km？s-1。第三签名图也是不变的，显示出比太阳梯度小20％的造粒速度梯度。第三个签名图的绝对偏移给出了经蓝移校正的径向速度3385？±70？m？s-1。 Fe Iλ6253线的二等分线图在面积上产生12％？±1％的通量赤字，比其他巨星小一些，但在4.8？km？s-1处峰的形状和位置与其他巨峰一致。巨人。所有研究的光球参数都与βGem一致，它是一个低发光的巨星，与其绝对大小一致。
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