A plethora of new R Coronae Borealis stars discovered from a dedicated spectroscopic follow-up survey
A plethora of new R Coronae Borealis stars discovered from a dedicated spectroscopic follow-up survey
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通过专门的光谱跟踪调查发现了大量新的 R Coronae Borealis 恒星
DOI：
10.1051/0004-6361/201834410
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发表时间：
2018
影响因子：
6.5
通讯作者：
A. Udalski
中科院分区：
文献类型：
--
作者：
P. Tisserand;G. Clayton;M. Bessell;D. Welch;D. Kamath;P. Wood;P. Wils;Ł. Wyrzykowski;P. Mróz;A. Udalski
上下文北冕座R星（R Coronae Borealis，RCB）是一种罕见的缺氢富碳超巨星，人们越来越怀疑它是中等质量区域（0.6 <MTot <1.2 M）CO/He白矮星双星合并的产物。 合并之后，短暂的酷超巨星阶段开始了。RCB星是非常罕见的，因为迄今为止银河系中只有77颗已知的RCB星，而人口合成模型预测的RCB星多达1000颗。
目标。我们的目标是显着增加已知的RCB恒星的数量，以便更好地了解它们的演化路径，空间分布和在人口合成结果的背景下形成率。一份2356颗RCB星星候选者的名单是使用全天空2 MASS和WISE巡天的红外颜色选出的。我们的目标是通过光谱对它们进行分类，从而将RCB星与其他产生尘埃的恒星区分开来。
方法.一系列的亮度和颜色的颜色削减，作为选择标准，然后使用已知的银河系和麦哲伦RCB星的样本进行测试。RCB光谱能量分布模型也被用来了解拱壳温度方面的每个选择标准的影响。获得了近500颗候选恒星的光学低分辨率光谱。这些光谱进行了比较，从一个新的网格MARC氢缺乏大气模型的合成光谱。这使我们能够根据RCB星的有效温度和光度状态定义RCB星的光谱分类系统。
结果该计划发现了45颗新的RCB星，包括30颗冷星（4000 <Teff <6800 K），14颗暖星（6800 <Teff <8500 K）和1颗热星（Teff> 15 000 K）。 其中40个属于银河系，5个位于麦哲伦星云。我们还证实了候选者KDM 5651确实是一颗新的RCB星星，使麦哲伦RCB恒星的总数增加到30颗。
结论.我们将已知的RCB恒星总数增加了50%，达到147颗。此外，我们编制了一份14个强RCB候选者的名单，最肯定的是在尘埃遮蔽阶段观察到的。从目前的探测效率和成功率来看，我们估计银河系中存在的RCB星不超过500颗，包括所有的HdC星。
Context. It is more and more suspected that R Coronae Borealis (RCB) stars – rare hydrogen-deficient and carbon-rich supergiant stars – are the products of mergers of CO/He white-dwarf binary systems in the intermediate mass regime (0.6 < MTot < 1.2 M⊙). Following the merger, a short-lived cool supergiant phase starts. RCB stars are extremely rare as only 77 have hitherto been known in the Galaxy, while up to 1000 have been predicted from population synthesis models.
Aims. The goal is to significantly increase the number of known RCB stars in order to better understand their evolutionary paths, their spatial distribution, and their formation rate in the context of population synthesis results. A list of 2356 RCB star candidates was selected using infrared colours from the all-sky 2MASS and WISE surveys. The objective is to follow them up spectroscopically to classify the candidates and, thus, to distinguish RCB stars from other dust-producing stars.
Methods. A series of brightness and colour-colour cuts that were used as selection criteria were then tested using the sample of known Galactic and Magellanic RCB stars. RCB spectral energy distribution models were also used to understand the effects of each selection criterion in terms of circumstellar shell temperature. Optical, low-resolution spectra were obtained for nearly 500 of the candidate stars. These spectra were compared to synthetic spectra from a new grid of MARCs hydrogen-deficient atmospheric models. This allowed us to define a spectroscopic classification system for RCB stars depending on their effective temperature and photometric status.
Results. This programme has found 45 new RCB stars, including 30 Cold (4000 < Teff < 6800 K), 14 Warm (6800 < Teff < 8500 K), and one Hot (Teff > 15 000 K). Forty of these belong to the Milky Way and five are located in the Magellanic Clouds. We also confirmed that the candidate KDM 5651 is indeed a new RCB star, increasing the total number of Magellanic RCB stars to 30.
Conclusions. We increased the total number of RCB stars known by ∼50%, bringing it up to 147. In addition, we compiled a list of 14 strong RCB candidates, most certainly observed during a dust obscuration phase. From the detection efficiency and success rate so far, we estimate that there should be no more than 500 RCB stars existing in the Milky Way, all HdC stars included.