标题： 利用最冷的Ae恒星限制 circumstellar 盘的粘度 显示英文标题

标题： Using the Coolest Ae Stars to Constrain Circumstellar Disk Viscosity

摘要： 经典Ae（CAe）星是主序A型恒星，具有H{\alpha }发射线但没有尘埃特征。它们被认为是经典Be星向较低质量的冷延伸。基于H{\alpha }光谱的最新调查显著增加了已知CAe星的数量，其范围扩展到凉爽至A4光谱类型（有效温度约为8500K）。我们计算了A型恒星周围气体盘的温度结构，包括来自中心恒星的辐射加热和盘旋转产生的粘性剪切加热。我们发现剪切加热对于A2及之后的光谱类型变得重要，并且可以增加由纯辐射加热盘所预测的低温。我们的建模表明，对于A2及之后的光谱类型，H{\alpha }发射线的存在和强度随着剪切加热量的增加而显著增强，我们提出这种依赖关系可以用来限制适合CAe星盘的{\alpha }粘性参数。 显示英文摘要

摘要： Classical Ae (CAe) stars are main sequence, A-type stars with H{\alpha} emission but no signature of dust. They are thought to be the cool extension of the classical Be stars to lower masses. Recent surveys based on H{\alpha} spectroscopy have significantly increased the number of known CAe stars, with the population extending to spectral types as cool as A4 (Teff approx. 8500 K). We compute the temperature structure of gaseous, circumstellar disks around A-type stars, including both radiative heating from the central star and viscous shear heating from the disk's rotation. We find that shear heating can become important for spectral types A2 and later and can act to increase the low temperatures predicted by purely radiatively heated disks. Our modeling indicates that the presence and strength of H{\alpha} emission for spectral types A2 and later significantly increases with the amount of shear heating included, and we propose that this dependence can be used to constrain the {\alpha} viscosity parameter appropriate for CAe star disks.