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CHROMOSPHERIC EMISSION IN METAL-POOR SOLAR-TYPE STARS

机译:贫金属太阳型恒星的大气辐射

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Cool stars like the Sun show chromospheric activity, which is largely attributed to nonradiative sources of energy linked to rotationally driven magnetic fields. However, a nonmagnetic process, such as dissipation of acoustic waves, may operate side by side with the first process. We report detections of chromospheric emission reversals in Mg 112800 A spectra for nine metal-poor solar-type stars, some believed to be among the oldest stars known, whose great age and slow rotation argue against strong magnetic activity. Although interstellar absorption is always present, in seven stars with high radial velocities each reversal profile is seen to be doubly peaked, with the blue peak stronger than the red, much like such profiles from the quiet Sun. Despite having as little as 1/300th as much metal as the Sun and being 3 times as old, these stars have chromospheric activity comparable to that in solar quiet regions. While these data do not rule out magnetic fields, they support an acoustic origin of chromospheric emission and show that relatively inactive solar-type stars of all ages have chromospheres whose characteristics are largely independent of metallicity.
机译:像太阳这样的凉爽恒星表现出色球活动,这主要归因于与旋转驱动磁场相关的非辐射能源。但是,非磁性过程(例如声波的消散)可能会与第一个过程并排运行。我们报告检测到9个金属贫乏的太阳型恒星中Mg 112800 A的色球层发射反转的光谱,其中一些恒星被认为是已知的最古老恒星之一,它们的年龄大且旋转慢,不利于强磁活动。尽管星际吸收一直存在,但在具有高径向速度的七颗恒星中,每个反向分布都被视为双峰,蓝色峰强于红色,就像来自安静太阳的分布一样。尽管这些恒星的金属含量仅为太阳的1/300,是旧太阳的3倍,但它们的色球活动性却与太阳安静地区相当。尽管这些数据不排除磁场,但它们支持色球层发射的声源,并表明各个年龄段相对不活跃的太阳型恒星具有色球层,其特征很大程度上与金属性无关。

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