与候选LBV MGE 042.0787+00.5084相关的缓慢扩展圆环
A slowly expanding torus associated with the candidate LBV MGE 042.0787+00.5084
摘要：
亮蓝变星（LBV）阶段是高质量恒星演化中一个知之甚少的阶段，其特点是短暂和不稳定。LBV恒星的周围环境是研究其致密恒星风和爆发质量损失事件的绝佳试验台。为了提高我们对LBV相位的认识，我们使用IRAM 30米射电望远镜在最近确定的候选LBV MGE 042.0787+00.5084周围的1.5 'x1.5'视场中观测了CO和$^{13}$ CO的J=1-0和J=2-1线。我们报告的第一个检测到的分子发射与此源，跟踪一个结构，具有明显的拱星分布。气体的形态和运动学可以用膨胀的环面来解释，这种结构可能起源于恒星喷出物或恒星风对母体分子云的作用。我们通过LTE和非LTE线模型推导出气体的物理性质，得到H $_2$的密度为10 $^3$ cm $^{-3}$，动力学温度低于100 K。此外，我们还建立了一个运动学模型来再现气体的结构和观测速度场，这与观测结果是一致的。我们估计的总分子气体质量为0.6 $\pm$ 0.1兆太阳和6 $\times$ 10 $^4$年的动力学年龄，导致0.8-1.2 $\times$ 10 $^{-5}$兆太阳年$^{-1}$的平均质量损失率。
英文摘要：
The luminous blue variable (LBV) phase is a poorly understood stage in the evolution of high mass stars, characterized for its brevity and instability. The surroundings of LBV stars are excellent test beds to study their dense stellar winds and eruptive mass-loss events. Aiming to improve our knowledge of the LBV phase, we observed the J=1-0 and J=2-1 lines of CO and $^{13}$CO in a field of 1.5'x1.5' around the recently identified candidate LBV MGE 042.0787+00.5084, using the IRAM 30-m radio telescope. We report the first detection of molecular emission associated with this source, tracing a structure with an evident circumstellar distribution. Morphology and kinematics of the gas can be explained by an expanding torus, a structure that may have originated from stellar ejecta or the action of stellar winds onto the parent molecular cloud. We derive the physical properties of the gas by means of LTE and non-LTE line modelling, obtaining densities of H$_2$ in the order of 10$^3$ cm$^{-3}$ and kinetic temperatures below 100 K. In addition, we build a kinematic model to reproduce the structure and observed velocity fields of the gas, which is in good agreement with the observations. We estimate a total molecular gas mass of 0.6$\pm$0.1 Msun and a dynamical age of 6$\times$10$^4$ years, leading to an average mass-loss rate of 0.8-1.2$\times$10$^{-5}$ Msun yr$^{-1}$.
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