标题： 研究Be壳星48天秤座的 circumstellar 盘 显示英文标题

标题： Investigating the Circumstellar Disk of the Be Shell Star 48 Librae

摘要： 在粘性去凝聚盘（VDD）模型中实现的全局盘振荡已被用来重现著名的Be星$\zeta$金牛座的大多数观测特性。 48天秤座与$\zeta$金牛座有若干相似之处——它们都是早期型Be星，在光谱中表现出壳特征，并显示周期性的$V/R$变化——但也有一些显著差异，比如密度更高且更扩展的盘，更长的$V/R$周期，以及缺乏所谓的三峰特征。 我们旨在用一个自洽的模型重现48天秤座的测光、偏振和光谱可观测量，并测试这一目标的全局振荡场景。 我们的计算使用了三维NLTE辐射转移代码HDUST完成。 我们采用了一个旋转变形、重力变暗的中心恒星，周围环绕着一个盘，该盘的未扰状态由VDD模型给出。 然后使用二维全局振荡代码计算盘的扰动，并将其叠加到未扰动的盘上。 通过VDD模型很好地拟合了盘的时间平均性质。 计算出的扰动周期为$P = 12$年，这与观测周期一致，扰动模型很好地再现了$V/R$周期的行为。 扰动模型改善了对测光数据的拟合，并重现了一些观测光谱数据的特征。 给出了对未来工作提高合成光谱的一些建议。 显示英文摘要

摘要： A global disk oscillation implemented in the viscous decretion disk (VDD) model has been used to reproduce most of the observed properties of the well known Be star $\zeta$ Tau. 48 Librae shares several similarities with $\zeta$ Tau -- they are both early-type Be stars, they display shell characteristics in their spectra, and they exhibit cyclic $V/R$ variations -- but has some marked differences as well, such as a much denser and more extended disk, a much longer $V/R$ cycle, and the absence of the so-called triple-peak features. We aim to reproduce the photometric, polarimetric, and spectroscopic observables of 48 Librae with a self-consistent model, and to test the global oscillation scenario for this target. Our calculations are carried out with the three-dimensional NLTE radiative transfer code HDUST. We employ a rotationally deformed, gravity-darkened central star, surrounded by a disk whose unperturbed state is given by the VDD model. A two-dimensional global oscillation code is then used to calculate the disk perturbation, and superimpose it on the unperturbed disk. A very good, self-consistent fit to the time-averaged properties of the disk is obtained with the VDD. The calculated perturbation has a period $P = 12$ yr, which agrees with the observed period, and the behaviour of the $V/R$ cycle is well reproduced by the perturbed model. The perturbed model improves the fit to the photometric data and reproduces some features of the observed spectroscopic data. Some suggestions to improve the synthesized spectroscopy in a future work are given.