论文标题
球状簇NGC 4147中紫外线明亮恒星的紫外线研究
UVIT study of UV bright stars in the globular cluster NGC 4147
论文作者
论文摘要
我们使用三个FUV过滤器，BAF2（F154W），Sapphire（F169M）和硅胶（F172M）在\ Mbox \ Mbox {\ Mbox {\ mbox {\ mbox {\ mbox {我们使用GAIA数据版本2（GAIA DR2）的适当动作确认了UVIT观察到的源的簇成员资格。我们使用紫外线色幅度级图（CMDS）鉴定了37个蓝色水平分支星（BHB），一颗蓝色Straggler Star（BSS）和15个变量恒星。我们发现所有FUV明亮的BHB都是第二代人的恒星。使用UV光学CMD，我们在群集中识别两个子群，BHB1和BHB2，在BHB1和BHB2的恒星计数比为24:13中，恒星计数比为24:13。 BHB1和BHB2的有效温度（T $ _ {\ Mathrm {eff}} $）是使用Basti-IAC零时代水平分支（ZAHB）的颜色 - 温度关系得出的。我们发现BHB1恒星比BHB2星更集中。我们还通过在光学和紫外线CMD上拟合年轻的basti-iacochrones来得出检测到的FUV明亮BSS的物理参数。
We present far ultraviolet (FUV) observations of globular cluster NGC 4147 using three FUV filters, BaF2 (F154W), Sapphire (F169M), and Silica (F172M) of Ultra-Violet Imaging Telescope (UVIT) on-board the \mbox{\em AstroSat} satellite. We confirmed the cluster membership of the UVIT observed sources using proper motions from Gaia data release 2 (GAIA DR2). We identified 37 blue horizontal branch stars (BHBs), one blue straggler star (BSS) and 15 variable stars using UV-optical color magnitude diagrams (CMDs). We find that all the FUV bright BHBs are second generation population stars. Using UV-optical CMDs, we identify two sub-populations, BHB1 and BHB2, among the UV-bright BHBs in the cluster with stars count ratio of 24:13 for BHB1 and BHB2. The effective temperatures (T$_{\mathrm{eff}}$) of BHB1 and BHB2 were derived using color-temperature relation of BaSTI-IAC zero-age horizontal branch (ZAHB). We found that BHB1 stars are more centrally concentrated than BHB2 stars. We also derive physical parameters of the detected FUV bright BSS by fitting younger age BaSTI-IAC isochrones on optical and UV-optical CMDs.
