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arXiv 0905.1690astro-ph.HEastro-ph.GAastro-ph.SR
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X射线光蒸发饥饿的Tauri T吸积

X-ray Photoevaporation-starved T Tauri Accretion

Jeremy J. Drake, Barbara Ercolano, Ettore Flaccomio, Giusi Micela

摘要:

观测到吸积的金牛座T星的X射线光度系统地低于非吸积星。对于这种效应,目前还没有被广泛接受的物理解释,尽管有人认为吸积在某种程度上抑制、干扰或掩盖了日冕X射线的活动。在这里,我们认为,相反的情况可能是:日冕X射线调制吸积流。我们重新研究了猎户座星云团中金牛座T星的X射线光度,发现不仅吸积恒星系统地变暗,而且质量吸积速率和恒星X射线光度之间存在相关性。我们使用Ercolano等人的X射线加热吸积盘模型来表明,原行星盘光蒸发质量损失率强烈依赖于恒星的X射线光度和足够高的吸积率竞争。X射线磁盘加热似乎提供了一个可行的机制,用于调制气体吸积流,并可能至少部分负责所观察到的吸积率和金牛座T星的X射线光度之间的相关性。

英文摘要:

X-ray luminosities of accreting T Tauri stars are observed to be systematically lower than those of non-accretors. There is as yet no widely accepted physical explanation for this effect, though it has been suggested that accretion somehow suppresses, disrupts or obscures coronal X-ray activity. Here, we suggest that the opposite might be the case: coronal X-rays modulate the accretion flow. We re-examine the X-ray luminosities of T Tauri stars in the Orion Nebula Cluster and find that not only are accreting stars systematically fainter, but that there is a correlation between mass accretion rate and stellar X-ray luminosity. We use the X-ray heated accretion disk models of Ercolano et al. to show that protoplanetary disk photoevaporative mass loss rates are strongly dependent on stellar X-ray luminosity and sufficiently high to be competitive with accretion rates. X-ray disk heating appears to offer a viable mechanism for modulating the gas accretion flow and could be at least partially responsible for the observed correlation between accretion rates and X-ray luminosities of T Tauri stars.

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