论文标题
大型麦哲伦云中C II排放线星星的调查
A Survey for C II Emission-Line Stars in the Large Magellanic Cloud
论文作者
论文摘要
我们提出了大型麦哲伦云的窄带成像调查，该调查旨在隔离CII $λλ$ 7231，7236发射线，如$ m _ {\ lambda7400} \ sim18 $。这项工作是由最初在第一个确认的静脉外[WC11]星的LMC中偶然发现的动机，该恒星的频谱以C II的发射为主，并且意识到此类物体的数量目前在很大程度上不受限制。该调查使用带频段和外滤波器成像$ \ sim $ 50 $〜$ deg $^2 $，将大大增加这些稀有恒星的总人口普查。此外，每个新的LMC [WC]恒星具有已知的光度，在银河样品中的数量非常不确定。多个已知的C II发射器很容易回收，从而验证了调查设计。我们发现38个新的C II排放候选者；需要完整样本的光谱以确定其性质。在初步的光谱侦察中，我们观察到三个候选者，每种候选者都在发现C II发射。一个是新的[WC11]。另一个显示了[WC11]的狭窄C II发射线的特征，但也显示了C IV，O V的广泛发射，以及HE II的特征[WC4]恒星的特征。我们推测这是二进制[WC]。第三个物体显示出弱的C II发射，但是频谱由密集的强吸收线（包括大量O II转变）的密集灌木丛主导。我们得出结论，这可能是一个不寻常的热，贫乏的后AGB恒星，可能是从[WC]到白矮人的过渡。即使缺乏完整的光谱程序，我们也可以推断出[WC]恒星并不能统治LMC行星星云的中心恒星，并且检测到的C II发射器在很大程度上是旧人口的。
We present a narrow-band imaging survey of the Large Magellanic Cloud, designed to isolate the C II $λλ$7231, 7236 emission lines in objects as faint as $m_{\lambda7400}\sim18$. The work is motivated by the recent serendipitous discovery in the LMC of the first confirmed extragalactic [WC11] star, whose spectrum is dominated by C II emission, and the realization that the number of such objects is currently largely unconstrained. The survey, which imaged $\sim$50$~$deg$^2$ using on-band and off-band filters, will significantly increase the total census of these rare stars. In addition, each new LMC [WC] star has a known luminosity, a quantity quite uncertain in the Galactic sample. Multiple known C II emitters were easily recovered, validating the survey design. We find 38 new C II emission candidates; spectroscopy of the complete sample will be needed to ascertain their nature. In a preliminary spectroscopic reconnaissance, we observed three candidates, finding C II emission in each. One is a new [WC11]. Another shows both the narrow C II emission lines characteristic of a [WC11], but also broad emission of C IV, O V, and He II characteristic of a much hotter [WC4] star; we speculate that this is a binary [WC]. The third object shows weak C II emission, but the spectrum is dominated by a dense thicket of strong absorption lines, including numerous O II transitions. We conclude it is likely an unusual hot, hydrogen-poor post-AGB star, possibly in transition from [WC] to white dwarf. Even lacking a complete spectroscopic program, we can infer that late [WC] stars do not dominate the central stars of LMC planetary nebulae, and that the detected C II emitters are largely of an old population.
