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arXiv 1502.01794astro-ph.SR
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NaSt1（WR 122）的多波长观测：相互作用Wolf-Rayet双星的赤道质量损失和X射线

Multiwavelength Observations of NaSt1 (WR 122): Equatorial Mass Loss and X-rays from an Interacting Wolf-Rayet Binary

Jon C. Mauerhan, Nathan Smith, Schuyler D. Van Dyk, Katie M. Morzinski, Laird M. Close, Philip M. Hinz, Jared R. Males, Timothy J. Rodigas

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Accepted to MNRAS on 2015 Feb 5; 14 pages, 9 figures (post-proof edit)
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摘要：

NaSt 1（又名Wolf-Rayet 122）是一颗特殊的发射线恒星，嵌入在一个具有致密尘埃核心的[N II]发射星云中。Crowther & Smith（1999）将该天体描述为一颗沃尔夫-拉叶星（WR），它被包裹在一个不透明的由hoc处理过的物质构成的星云中，可能类似于Eta Car和它的Homunculus星云，只是有一个更热的中心源。为了辨别[N II]星云的形态，我们使用哈勃太空望远镜和宽视场相机3进行了窄带成像。图像显示，该星云有一个从边缘倾斜12度的盘状几何形状，由一个明亮的中央椭圆体组成，周围环绕着一个更大的星云环。地面光谱显示了星云主轴外部附近的径向速度结构（~10 km/s），这可能是流出气体的印记。近红外自适应光学成像与麦哲伦AO解决了一个紧凑的椭球体的KS波段发射对准较大的[N II]星云，我们怀疑这是分散的He I线发射（2.06 μ m）的结果。钱德拉X射线天文台的观测显示，在星云核心有一个X射线点源，在能量<1 keV时被大量吸收，其性质与WR星和碰撞风双星一致。我们认为，NaSt 1是一个WR的二进制嵌入在赤道外流，形成的非保守的质量转移的结果。因此，NaSt 1似乎是一个罕见的和重要的例子，一个剥离信封WR形成通过二进制相互作用，陷入短暂的罗什瓣溢出阶段。

英文摘要：

NaSt1 (aka Wolf-Rayet 122) is a peculiar emission-line star embedded in an extended nebula of [N II] emission with a compact dusty core. This object was characterized by Crowther & Smith (1999) as a Wolf-Rayet (WR) star cloaked in an opaque nebula of CNO-processed material, perhaps analogous to Eta Car and its Homunculus nebula, albeit with a hotter central source. To discern the morphology of the [N II] nebula we performed narrowband imaging using the Hubble Space Telescope and Wide-field Camera 3. The images reveal that the nebula has a disk-like geometry tilted 12 degrees from edge-on, composed of a bright central ellipsoid surrounded by a larger clumpy ring. Ground-based spectroscopy reveals radial velocity structure (~10 km/s) near the outer portions of the nebula's major axis, which is likely to be the imprint of outflowing gas. Near-infrared adaptive-optics imaging with Magellan AO has resolved a compact ellipsoid of Ks-band emission aligned with the larger [N II] nebula, which we suspect is the result of scattered He I line emission (2.06 um). Observations with the Chandra X-ray Observatory have revealed an X-ray point source at the core of the nebula that is heavily absorbed at energies <1 keV and has properties consistent with WR stars and colliding-wind binaries. We suggest that NaSt1 is a WR binary embedded in an equatorial outflow that formed as the result of non-conservative mass transfer. NaSt1 thus appears to be a rare and important example of a stripped-envelope WR forming through binary interaction, caught in the brief Roche-lobe overflow phase.

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