论文标题
使用Astrosat-ultra紫色成像望远镜研究的球形群集NGC 5053的恒星种群
Stellar populations of the globular cluster NGC 5053 investigated using AstroSat-Ultra Violet Imaging Telescope
论文作者
论文摘要
球形簇是老式的，密集的包装是测试恒星进化论的理想实验室。尽管在光条带上有有关球形簇的巨大文献，但紫外线（UV）制度的研究很少。 In this work, we study the stellar populations of a metal poor and a rather dispersed globular cluster, NGC 5053, using the UV instrument of AstroSat, namely the Ultra Violet Imaging Telescope in three far-UV (F154W, F169M, F172M) and three near-UV (N219M, N245M, N263M) filters.在这些图像上进行了光度法，以构建紫外线的目录，其中使用GAIA EDR3目录鉴定了群集成员。紫外线和光学CMD可帮助我们找到已知的恒星种群，例如BHB星，RR-Lyrae Star，RHB星，BSSS，SX-PHE，RGB和AGB星。根据他们在CMD中的位置，我们确定了8个新的BSS候选者，6个可能的EBSSS和一个EHB候选者。通过将光谱能量分布与出色的大气模型拟合来证实它们的性质。我们认为，根据我们对径向分布和SED的分析，该集群的BSS人口可能具有碰撞的起源。生成了Basti-IAC等时线来表征簇特性，我们发现群集成员的亮度和颜色最适合拟合，该模型具有α实现的型号，氦分数为0.247，金属性为-1.9 dex和年龄在10.5-14.5 gyr的范围内。
Globular clusters being old and densely packed serve as ideal laboratories to test stellar evolution theories. Although there is enormous literature on globular clusters in optical bands, studies in the ultraviolet (UV) regime are sparse. In this work, we study the stellar populations of a metal poor and a rather dispersed globular cluster, NGC 5053, using the UV instrument of AstroSat, namely the Ultra Violet Imaging Telescope in three far-UV (F154W, F169M, F172M) and three near-UV (N219M, N245M, N263M) filters. Photometry was carried out on these images to construct a catalogue of UV stars, of which the cluster members were identified using Gaia EDR3 catalogue. UV and optical CMDs help us locate known stellar populations such as BHB stars, RR-Lyrae stars, RHB stars, BSSs, SX-Phe, RGB and AGB stars. Based on their locations in the CMDs, we have identified 8 new BSS candidates, 6 probable eBSSs, and an EHB candidate. Their nature has been confirmed by fitting their spectral energy distributions with stellar atmospheric models. We believe the BSS population of this cluster is likely to have a collisional origin based on our analyses of their radial distribution and SEDs. BaSTI-IAC isochrones were generated to characterize the cluster properties, and we find that the observed brightness and colours of cluster members are best-fit with a model that is alpha-enhanced with a helium fraction of 0.247, metallicity of -1.9 dex and age within a range of 10.5-14.5 Gyr.
