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首页> 外文期刊>The Astrophysical journal >STELLAR ACTIVITY AT THE END OF THE MAIN SEQUENCE: GHRS OBSERVATIONS OF THE M8 Ve STAR VB 10
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STELLAR ACTIVITY AT THE END OF THE MAIN SEQUENCE: GHRS OBSERVATIONS OF THE M8 Ve STAR VB 10

机译：主要序列末尾的星状活动：M8 Ve STAR VB 10的GHRS观测

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摘要

We present Goddard High Resolution Spectrograph observations of the M8 Ve star VB 10 ( = G1 752B), located very near the end of the stellar main sequence, and its dM3.5 binary companion G1 752A. These coeval stars provide a test bed for studying whether the outer atmospheres of stars respond to changes in internal structure as stars become fully convective near mass 0.3 solar mass (about spectral type M5), where the nature of the stellar magnetic dynamo presumably changes, and near the transition from red to brown dwarfs near mass 0.08 solar mass (about spectral type M9), when hydrogen burning ceases at the end of the main sequence. We obtain upper limits for the quiescent emission of VB 10 but observe a transition region spectrum during a large flare, which indicates that some type of magnetic dynamo must be present. Two indirect lines of evidence—scaling from the observed X-ray emission and scaling from a time-resolved flare on AD Leo— suggest that the fraction of the stellar bolometric luminosity that heats the transition region of VB 10 outside of obvious flares is comparable to, or larger than, that for G1 752A. This suggests an increase in the magnetic heating rates, as measured by L_(line)/L_(bol) ratios, across the radiative/convective core boundary and as stars approach the red/brown dwarf boundary. These results provide new constraints for dynamo models and models of coronal and transition-region heating in late-type stars.
机译：我们展示了位于恒星主序列末端非常近的M8 Ve星VB 10（= G1 752B）及其dM3.5双星伴星G1 752A的戈达德高分辨率光谱仪观测结果。这些近代恒星为研究恒星的外部大气是否响应内部结构的变化提供了实验平台，因为恒星在质量约为0.3太阳质量（大约M5的光谱类型）附近完全对流时，恒星发电机的性质可能会发生变化，并且当在主序列的末尾停止氢燃烧时，在从红矮星到红矮星的过渡附近，质量接近太阳质量0.08（约为光谱类型M9）。我们获得了VB 10静态发射的上限，但在大火炬期间观察到过渡区频谱，这表明必须存在某种类型的磁发电机。两条间接证据线-从观察到的X射线发射缩放和从AD Leo上时间分辨的耀斑缩放-表明恒星辐射热度加热了明显耀斑之外的VB 10过渡区域的比例与，或大于G1 752A。这表明，通过辐射/对流核心边界和恒星接近红/棕矮星边界时，通过L_（线）/ L_（bol）比测量的磁加热速率会增加。这些结果为发电机模型以及晚型恒星的日冕和过渡区加热模型提供了新的约束。

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