论文标题
UOCS VII。蓝色散乱的开放群集NGC 7789与紫外线/Astrosat的种群
UOCS VII. Blue Straggler Populations of Open Cluster NGC 7789 with UVIT/AstroSat
论文作者
论文摘要
NGC 7789是$ \ sim $ 1.6 Gyr Old，人口稠密的开放群集，位于$ \ sim $ 2000 PC。我们使用来自紫外线/astrosat的Ultraviolet（UV）数据来表征该集群的蓝色Straggler星（BSS）。我们提出了使用从UV到IR波长的多波长数据构建的15个BSS候选者的光谱能分布（SED）。在8个BSS候选物中，发现单个温度SED令人满意。我们在5个BSS候选人中发现了热门同伴。 Teff $ \ sim $ 11750-15500 k，r $ \ sim $ 0.069-0.242 r $ _ {\ odot} $和l $ \ sim $ 0.25-1.55 l $ _ {\ odot} $，与sim（Elm Mass（Elm）较小的白色dwarfs（wds）相比， m $ _ {\ odot} $，从而确认了邮政传输系统。我们在BSS形成机制的背景下讨论了这一发现的含义。另外两个BS在一个或多个紫外线过滤器中显示出多余的BS，并且可能有一个热的伴侣，但是，我们无法表征它们。我们建议在该群集中研究的15个候选物（33％）中至少有5个是通过传质机制形成的。
NGC 7789 is a $\sim$1.6 Gyr old, populous open cluster located at $\sim$2000 pc. We characterize the blue straggler stars (BSS) of this cluster using the Ultraviolet (UV) data from the UVIT/AstroSat. We present spectral energy distributions (SED) of 15 BSS candidates constructed using multi-wavelength data ranging from UV to IR wavelengths. In 8 BSS candidates, a single temperature SED is found to be satisfactory. We discover hot companions in 5 BSS candidates. The hot companions with Teff $\sim$11750-15500 K, R $\sim$0.069-0.242 R$_{\odot}$, and L $\sim$0.25-1.55 L$_{\odot}$, are most likely extremely low mass (ELM) white dwarfs (WDs) with masses smaller than $\sim$0.18 M$_{\odot}$, and thereby confirmed post mass transfer systems. We discuss the implication of this finding in the context of BSS formation mechanisms. Two additional BSS show excess in one or more UV filters, and may have a hot companion, however, we are unable to characterize them. We suggest that at least 5 of the 15 BSS candidates (33%) studied in this cluster have formed via the mass transfer mechanism.
