论文标题
Globules-IV。 NGC 362中的紫色/Astrosat检测极低的质量白矮人伴侣与蓝色Straggler星星
GlobULeS-IV. UVIT/AstroSat detection of extremely low mass white dwarf companions to blue straggler stars in NGC 362
论文作者
论文摘要
我们报告了使用Astrosats Ultra Ultra Violet Imageing望远镜（UVIT）的图像，报告了在银河球状球形群集NGC 362中发现极低的质量白矮人（ELM WDS）作为蓝色Straggler星（BSS）的同伴。使用UVIT，UVOT，GAIA EDR3和2.2 M ESO/MPI望远镜的数据创建了26个FUV明亮成员BSS的光谱能量分布（SED）。单个SED安装在14个BSS中，而双SED拟合在研究的26个BSSS中有12位露出ELM WD为二元同伴。发现12 ELM WD的有效温度，半径，亮度和质量具有范围（TEFF = 9750-18000 K，r = 0.1-0.4 RSUN，L = 0.4-3.3 LSUN，M = 0.16-0.20 MSUN）。这些表明12个BSS是通过案例A/B传质途径形成的质量转移系统。据我们所知，这是ELM WD作为球形簇中BSS伴侣的第一个发现。已知该群集具有二进制BSS序列，而12个二进制和14个单个BSS（由SED分类）遵循BSS在颜色数字图中的传质和碰撞序列。发现9个ELM WD的冷却年龄比500 Myr年轻。尽管二进制BSS可能在核心崩溃（大约200 MYR）或作为集群动力学演化的一部分中形成，但它们为该群集的动力学提供了新的见解。
We report the discovery of extremely low-mass white dwarfs (ELM WDs) as a companion of blue straggler stars (BSSs) in the Galactic globular cluster NGC 362 using images from AstroSats Ultra Violet Imaging Telescope (UVIT). Spectral Energy Distributions (SEDs) for 26 FUV bright member BSSs are created using data from the UVIT, UVOT, Gaia EDR3, and the 2.2 m ESO/MPI telescope. A single SED is fitted to 14 BSSs, whereas double-SED fits revealed ELM WDs as binary companions in 12 of the 26 BSSs studied. The effective temperature, radius, luminosity and mass of the 12 ELM WDs are found to have a range (Teff = 9750-18000 K, R = 0.1-0.4 Rsun, L = 0.4-3.3 Lsun, and M =0.16-0.20 Msun). These suggest that 12 BSSs are post-mass-transfer systems formed through Case A/B mass transfer pathway. To the best of our knowledge, this is the first finding of ELM WDs as companions to BSS in globular clusters. This cluster is known to have a binary BSS sequence and the 12 binary and 14 single BSSs (as classified by the SEDs) follow the mass transfer and collisional sequence of BSS in the colour-magnitude diagram. The cooling ages of 9 of the ELM WDs are found to be younger than 500 Myr. Though the binary BSSs may have formed during the core-collapse (approx 200 Myr) or as part of the dynamical evolution of the cluster, they provide new insights on the dynamics of this cluster.
