标题： 利用印度汉坦山查德拉望远镜研究银河系经典B型Be星的巴尔末减缩量 显示英文标题

标题： Study of the Balmer decrements for Galactic classical Be stars using the Himalayan Chandra Telescope of India

摘要： 近期，Banerjee 等人（2021）利用位于印度拉达克的2米口径喜马拉雅·昌德拉望远镜（HCT）设备，对115颗银河系场星中所有主要发射线编制了目录。本文介绍了我们对这些恒星的进一步研究，以估算其盘面中的电子密度。我们的研究基于巴尔末消光比值表明，这些恒星的盘面通常具有光学厚的性质，大约65%的恒星其周围星周包层（CEs）中的电子密度（n_e）超过10^13 cm^-3。对于另外19%的恒星，其盘面中的平均n_e可能在10^12 cm^-3到10^13 cm^-3之间。我们注意到，H{\alpha }和 H\b{eta}线轮廓的性质可能不会影响所观测到的样本恒星的巴尔末消光比值（即D_34和D_54）。有趣的是，我们还发现约50%显示出D_34大于2.7的Be型恒星属于较早的光谱类型，即在B0-B3范围内。 显示英文摘要

摘要： In a recent study, Banerjee et al. (2021) produced an atlas of all major emission lines found in a large sample of 115 Galactic field Be stars using the 2-m Himalayan Chandra Telescope (HCT) facility located at Ladakh, India. This paper presents our further exploration of these stars to estimate the electron density in their discs. Our study using Balmer decrement values indicate that their discs are generally optically thick in nature with electron density (n_e) in their circumstellar envelopes (CEs) being in excess of 10^13 cm^-3 for around 65% of the stars. For another 19% stars, the average n_e in their discs probably range between 10^12 cm^-3 and 10^13 cm^-3. We noticed that the nature of the H{\alpha} and H\b{eta} line profiles might not influence the observed Balmer decrement values (i.e. D_34 and D_54) of the sample of stars. Interestingly, we also found that around 50% of the Be stars displaying D_34 greater than 2.7 are of earlier spectral types, i.e. within B0 -B3.