标题： VY CMa的最后阶段：孔径综合与自适应光学成像 显示英文标题

标题： The last gasps of VY CMa: Aperture synthesis and adaptive optics imagery

摘要： 我们报告了红超巨星VY CMa在1.25微米、1.65微米、2.26微米、3.08微米和4.8微米波段的新观测结果。采用了两种互补的观测技术：利用凯克I望远镜（10米）上的非冗余孔径掩模获得内区图像，其分辨率前所未有；以及利用拉西拉欧洲南方天文台3.6米望远镜上的自适应光学成像，在宽视场内达到极高的（约10^5）信噪比动态范围。 首次在近红外波段解析出内尘壳，并揭示出距离恒星0.1"（约15个R_star）以内的一侧延伸的星周辐射。 估计了星周尘壳在1.65微米、2.26微米和3.08微米波段的视线光学深度，分别为1.86±0.42、0.85±0.20和0.44±0.11。 这些新结果使得独立于尘壳几何结构估算VY CMa的总光度成为可能，得到L_star ≈ 2×10^5 L_sun。 在从中心源延伸至4"范围内的暗弱扩展星云中观察到了多种尘凝聚体，包括一个大尺度的散射羽状结构和弓形尘特征。 虽然羽状结构的起源尚不确定，但假设该羽状结构是由以旋转流注入点为中心的径向驱动尘粒形成，且旋转周期介于1200至4200年之间（可能是恒星自转周期或不可见伴星轨道周期），提出了一个几何模型。 显示英文摘要

摘要： We present new observations of the red supergiant VY CMa at 1.25 micron, 1.65 micron, 2.26 micron, 3.08 micron and 4.8 micron. Two complementary observational techniques were utilized: non-redundant aperture masking on the 10-m Keck-I telescope yielding images of the innermost regions at unprecedented resolution, and adaptive optics imaging on the ESO 3.6-m telescope at La Silla attaining extremely high (~10^5) peak-to-noise dynamic range over a wide field. For the first time the inner dust shell has been resolved in the near-infrared to reveal a one-sided extension of circumstellar emission within 0.1" (~15 R_star) of the star. The line-of-sight optical depths of the circumstellar dust shell at 1.65 micron, 2.26 micron, and 3.08 micron have been estimated to be 1.86 +/- 0.42, 0.85 +/- 0.20, and 0.44 +/- 0.11. These new results allow the bolometric luminosity of VY~CMa to be estimated independent of the dust shell geometry, yielding L_star ~ 2x10^5 L_sun. A variety of dust condensations, including a large scattering plume and a bow-shaped dust feature, were observed in the faint, extended nebula up to 4" from the central source. While the origin of the nebulous plume remains uncertain, a geometrical model is developed assuming the plume is produced by radially-driven dust grains forming at a rotating flow insertion point with a rotational period between 1200-4200 years, which is perhaps the stellar rotational period or the orbital period of an unseen companion.