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arXiv 1301.7210astro-ph.SR
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探测热亚矮星O型星2 MASS J19310888 +4324577周围的多壳层行星状星云

Detection of a multi-shell planetary nebula around the hot subdwarf O-type star 2MASS J19310888+4324577

A. Aller, L. F. Miranda, A. Ulla, R. Vázquez, P. F. Guillén, L. Olguín, C. Rodríguez-López, P. Thejll, R. Oreiro, M. Manteiga, E. Pérez

摘要:

自1947年发现以来,热亚矮星O型星(sdOs)的起源仍然不清楚。其中,后渐近巨分支(post-AGB)起源是可能的一小部分sdO。我们参与了一项正在进行的全面研究,以寻找和分析sdOs周围的行星状星云(PNE),目的是确定sdOs的分数和属性与后AGB起源。我们使用深Halalpha和[OIII]图像的sdO探测星云发射和中间分辨率,长狭缝光谱检测星云和他们的sdO中心恒星。这些数据与其他观测数据相辅相成,以便对探测到的星云进行进一步分析。我们报告了在2 MASS J19310888+4324577(2 M1931 +4324)周围探测到一个极其微弱的复杂PN,这是一个双星系统中被归类为sdO的恒星。PN显示了一个双极和一个椭圆形的外壳,其主轴方向相互垂直,以及两个外壳外的高激发结构。WISE存档图像显示了星云内部区域12和22微米的微弱扩展发射。星云内部的运动学与双极和圆柱/椭球壳一致,在这两种情况下,主轴主要垂直于视线。星云光谱只显示出H α、H β和[OIII] 4959,5007发射线,但显示出非常低的激发([OIII]/H β = 1.5),与没有低激发发射线形成强烈对比。2 M1931 +4324的光谱呈现出窄的电离氦谱,证实了以前的sdO分类,并表明有效温度>= 60000 K。2 M1931 +4324的双星性质,它与复杂PN的关联,以及该系统的几个性质,为双星中心星是复杂PN形成的关键成分的想法提供了强有力的支持。

英文摘要:

(Abridged) The origin of hot subdwarf O-type stars (sdOs) remains unclear since their discovery in 1947. Among others, a post-Asymptotic Giant Branch (post-AGB) origin is possible for a fraction of sdOs. We are involved in a comprehensive ongoing study to search for and to analyze planetary nebulae (PNe) around sdOs with the aim of establishing the fraction and properties of sdOs with a post-AGB origin. We use deep Halpha and [OIII] images of sdOs to detect nebular emission and intermediate resolution, long-slit optical spectroscopy of the detected nebulae and their sdO central stars. These data are complemented with other observations for further analysis of the detected nebulae. We report the detection of an extremely faint, complex PN around 2MASS J19310888+4324577 (2M1931+4324), a star classified as sdO in a binary system. The PN shows a bipolar and an elliptical shell, whose major axes are oriented perpendicular to each other, and high-excitation structures outside the two shells. WISE archive images show faint, extended emission at 12 and 22 microns in the inner nebular regions. The internal nebular kinematics is consistent with a bipolar and a cylindrical/ellipsoidal shell, in both cases with the main axis mainly perpendicular to the line of sight. The nebular spectrum only exhibits Halpha, Hbeta and [OIII]4959,5007 emission lines, but suggests a very low-excitation ([OIII]/Hbeta = 1.5), in strong contrast with the absence of low-excitation emission lines. The spectrum of 2M1931+4324 presents narrow, ionized helium absorptions that confirm the previous sdO classification and suggest an effective temperature >= 60000 K. The binary nature of 2M1931+4324, its association with a complex PN, and several properties of the system provide strong support for the idea that binary central stars are a crucial ingredient in the formation of complex PNe.

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