论文标题
紫外成像望远镜（UVIT）观察银河球状簇NGC 7492
Ultraviolet Imaging Telescope (UVIT) observation of the Galactic Globular Cluster NGC 7492
论文作者
论文摘要
我们使用用两种远欧特维洛莱特（FUV：1300-1800Å）和三个近距离粉状物（NUV：2000-3000-3000Å）紫外线成像（UVIT）上的详细数据介绍了银河球状簇NGC 7492的详细光度观测结果。我们使用GAIA数据释放2（GAIA DR2）正确的运动数据确认了提取源的群集成员资格。我们已经使用紫外线图（CMD）使用了紫外线和盖亚过滤器，以分离群集中存在的恒星的不同进化阶段。我们已经使用UV和UV-Optical CMD在集群的核心中确定了一个新的极端水平分支（EHB）恒星。群集的估计距离模数为$ 16.95 \ pm0.05 $，通过与群集参数拟合basti iSochrones获得，$ [fe/h] = -1.8 $ dex and age $ = 12.0 $ $ = 12.0 $ gyr v $ - $ - $ - $ - $ $ i vs vs v cmd。有趣的是，在紫外线过滤器中仅检测到UV-Bright热源中的EHB恒星和蓝色水平分支星（BHB）。我们使用颜色温度的关系和多波段过滤器的频谱能量分布（SED）得出了BHB的有效温度，该温度在8,000 k至10,500 k的范围内。我们发现，通过安装Basti Zahb，我们发现BHB的丰度变化。对应于最佳拟合等速线的BHB的HE丰度的范围为0.247至0.350。我们已经估计了使用SED拟合和HB后进化轨迹在集群中新鉴定的EHB星的各种物理参数。我们研究了在紫外线中检测到的簇的所有来源的径向分布。 FUV过滤器中检测到的来源延伸到集群的半径半径（1.15 $'$），而在NUV过滤器中检测到的源延伸到了群集的潮汐半径（9.2 $'$）之外。
We present detailed photometric observations of the Galactic globular cluster NGC 7492 using the data obtained with two far-ultraviolet (FUV: 1300 - 1800 Å) and three near-ultraviolet (NUV: 2000 - 3000 Å) filters of Ultraviolet Imaging Telescope (UVIT) on-board the \textit{AstroSat} satellite. We confirmed the cluster membership of the extracted sources using GAIA data release 2 (Gaia DR2) proper motion data. We have used color-magnitude diagrams (CMDs) using UVIT and GAIA filters to separate out different evolutionary stages of the stars present in the cluster. We have identified a new extreme horizontal branch (EHB) star at the core of the cluster using UV and UV-optical CMDs. The estimated distance-modulus of the cluster is $16.95\pm0.05$ obtained by fitting BaSTI isochrones with cluster parameters, $[Fe/H] = -1.8$ dex and age $= 12.0$ Gyr on the V $-$ I vs V CMD. Interestingly, only the EHB star and blue horizontal branch stars (BHBs) among the UV-bright hot sources are detected in FUV filters of UVIT. We have derived the effective temperature of BHBs using color-temperature relation and spectral energy distributions (SEDs) of multi-band filters, which are in the range from 8,000 K to 10,500 K. We find a variation of He abundance of BHBs by fitting the BaSTI ZAHB. The range in the He abundance of the BHBs corresponding to the best fit isochrones is 0.247 to 0.350. We have estimated various physical parameters of the newly identified EHB star in the cluster using SED fit and post-HB evolutionary tracks. We have studied the radial distribution of all the sources of the cluster detected in UVIT. The sources detected in FUV filters extend beyond the half light radius (1.15$'$) of the cluster, whereas the sources detected in NUV filters extend beyond the tidal radius (9.2$'$) of the cluster.
