猎户座σ星中古老光蒸发盘的发现
Discovery of an old photoevaporating disk in sigma Orionis
摘要：
星周盘的光蒸发是猎户座恒星起源处盘耗散的一个强有力的过程。这封信报告了第一次检测到一个光蒸发盘在其演变的最后但长期的阶段。该盘与猎户座σ星系团的低质量金牛座T成员有关。它的特点是吸积率非常低（如果有的话），并且有微弱的光蒸发风（Mloss ~ 10^{-9} Msun/yr），这在该天体的光谱中可以清楚地探测到。恒星风发出强烈的[SII]和[NII]禁戒线，因为低质量恒星靠近一个强大的电离光子源，O9.5恒星猎户座σ。
英文摘要：
The photoevaporation of circumstellar disks is a powerful process in the disk dissipation at the origin of the Orion proplyds. This Letter reports the first detection of a photoevaporating disk in the final but long-lasting phase of its evolution. The disk is associated to a low-mass T Tauri member of the sigma Orionis Cluster. It is characterized by a very low (if any) accretion rate and by a tenuous (Mloss ~ 10^{-9} Msun/yr) photoevaporation wind, which is unambiguously detected in the optical spectrum of the object. The wind emits strong forbidden lines of [SII] and [NII] because the low-mass star is close to a powerful source of ionizing photons, the O9.5 star sigma Ori.
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