论文标题
用$ n $ body模拟调查明星簇中的紫外线效果：未来CSST观察的预测
Investigating the UV-excess in star clusters with $N$-body simulations: predictions for future CSST observations
论文作者
论文摘要
我们使用PETAR使用PETAR，使用n = 10k和n = 100k（单星和二元系统）的六个簇和n = 100k（单恒星和二元系统）的六个簇和n = 100k（单星和二元系统）的N体仿真来研究恒星簇中的UV效果的起源。所有模型最初都有50％的原始二元分数。使用galevnb，我们将模拟数据转换为中国空间站望远镜（CSST）和哈勃太空望远镜（HST）的合成光谱和光度法。从光谱能量分布中，我们确定了有助于紫外线效果的三个恒星种群：（1）第二渐近巨型分支恒星，它们在早期有助于紫外线； （2）裸氦星和（3）白色矮人，它们是FUV光谱的长期贡献者。由白矮人和主要恒星组成的二进制恒星是灾难性变量（CV）候选者。 CV候选物的幅度分布最多为2 Gyr。 FUV-NUV中明亮的简历群体特别明亮。我们的模型簇的Fuv-nuv颜色是1-2 mag红色，比M 87和银河系中的紫外线液簇。在观察到的簇中，可以通过氦富集引起这种差异。我们的模拟基于简单的恒星进化。我们不包括氦气和光元素或多个恒星种群的变化的影响。对于所有颜色差为0.2-0.5 mag，高达4个半质量半径的主序列的恒星，CSST NUV-Y中存在正径向颜色梯度。 CSST NUV-G颜色与NUV-G> 1 mag的HST FUV-NUV密切相关，线性关系$ fuv-nuv =（1.09 \ pm0.12）\ times \ times（nuv-g）+（ - 1.01 \ pm0.22）$。这允许将未来的CSST NUV-G颜色转换为HST FUV-NUV颜色，这些颜色对UV-Excess功能敏感。我们发现，CSST将能够检测出> 200 MYR年龄> 200 MYR的银河/半乳酸星形簇中的紫外线。
We study the origin of the UV-excess in star clusters by performing N-body simulations of six clusters with N=10k and N=100k (single stars & binary systems) and metallicities of Z=0.01, 0.001, and 0.0001, using PETAR. All models initially have a 50 percent primordial binary fraction. Using GalevNB we convert the simulated data into synthetic spectra and photometry for the China Space Station Telescope (CSST) and Hubble Space Telescope (HST). From the spectral energy distributions we identify three stellar populations that contribute to the UV-excess: (1) second asymptotic giant branch stars, which contribute to the UV flux at early times; (2) naked helium stars, and (3) white dwarfs, which are long-term contributors to the FUV spectra. Binary stars consisting of a white dwarf and a main-sequence star are cataclysmic variable (CV) candidates. The magnitude distribution of CV candidates is bimodal up to 2 Gyr. The bright CV population is particularly bright in FUV-NUV. The FUV-NUV color of our model clusters is 1-2 mag redder than the UV-excess globular clusters in M 87 and in the Milky Way. This discrepancy may be induced by helium enrichment in observed clusters. Our simulations are based on simple stellar evolution; we do not include the effects of variations in helium and light elements or multiple stellar populations. A positive radial color gradient is present in CSST NUV-y for main-sequence stars of all models with a color difference of 0.2-0.5 mag, up to 4 half-mass radii. The CSST NUV-g color correlates strongly with HST FUV-NUV for NUV-g>1 mag, with the linear relation $FUV-NUV=(1.09\pm0.12)\times(NUV-g)+(-1.01\pm0.22)$. This allows for conversion of future CSST NUV-g colors into HST FUV-NUV colors, which are sensitive to UV-excess features. We find that CSST will be able to detect UV-excess in galactic/extra-galactic star clusters with ages >200 Myr.
