PROTOPLANETARY DISK SHADOWING BY GAS INFALLING ONTO THE YOUNG STAR AK Sco
PROTOPLANETARY DISK SHADOWING BY GAS INFALLING ONTO THE YOUNG STAR AK Sco
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DOI：
10.3847/2041-8205/818/1/l17
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发表时间：
2016-02
期刊：
影响因子：
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通讯作者：
A. Castro;R. Loyd;K. France;A. Sytov;D. Bisikalo
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作者：
A. Castro;R. Loyd;K. France;A. Sytov;D. Bisikalo
年轻的太阳型恒星在主序前（PMS）演化过程中通过星周盘物质的吸积而成长。在这个过程中产生的紫外线辐射在年轻行星盘的化学和进化中起着关键作用。特别是，氢Lyα线（Lyα）通过驱动控制盘演化的光蒸发流来蚀刻盘表面。我们利用哈勃太空望远镜对PMS双星AK Sco进行了观测，发现H2通量下降了10%，持续时间为5.9小时。我们证明H2通量的减少可以由恒星Lyα光子被来自3r * ？>。考虑到Lyα线的高光学深度，一个非常低的气体柱N H > 5 × 10 17 ？> cm−2足以阻挡Lyα辐射，而不会对其余的恒星光谱示踪剂产生明显的影响。
Young solar-type stars grow through the accretion of material from the circumstellar disk during pre-main-sequence (PMS) evolution. The ultraviolet radiation generated in this process plays a key role in the chemistry and evolution of young planetary disks. In particular, the hydrogen Lyα line (Lyα) etches the disk surface by driving photoevaporative flows that control disk evolution. Using the Hubble Space Telescope, we have monitored the PMS binary star AK Sco during the periastron passage and have detected a drop of the H2 flux by up to 10% lasting 5.9 hr. We show that the decrease of the H2 flux can be produced by the occultation of the stellar Lyα photons by a gas stream in free fall from 3 R * ?> . Given the high optical depth of the Lyα line, a very low gas column of N H > 5 × 10 17 ?> cm−2 suffices to block the Lyα radiation without producing noticeable effects in the rest of the stellar spectral tracers.