Emission lines from Rydberg transitions are detected for the first time from a region close to the surface of Betelgeuse. The H30α line is observed at 231.905 GHz, with an FWHM ∼42 km s⁻¹ and extended wings. A second line at 232.025 GHz (FWHM ∼21 km s⁻¹ ), is modeled as a combination of Rydberg transitions of abundant low first ionization potential metals. Both H30α and the Rydberg combined line X30α are fitted by Voigt profiles, and collisional broadening with electrons may be partly responsible for the Lorentzian contribution, indicating electron densities of a few 10⁸ cm⁻³. X30α is located in a relatively smooth ring at a projected radius of 0.9× the optical photospheric radius R _⋆, whereas H30α is more clumpy, reaching a peak at ∼1.4 R _⋆. We use a semiempirical thermodynamic atmospheric model of Betelgeuse to compute the 232 GHz (1.29 mm) continuum and line profiles making simple assumptions. Photoionized abundant metals dominate the electron density, and the predicted surface of continuum optical depth unity at 232 GHz occurs at ∼1.3 R _⋆, in good agreement with observations. Assuming a Saha–Boltzmann distribution for the level populations of Mg, Si, and Fe, the model predicts that the X30α emission arises in a region of radially increasing temperature and turbulence. Inclusion of ionized C and non-LTE effects could modify the integrated fluxes and location of emission. These simulations confirm the identity of the Rydberg transition lines observed toward Betelgeuse and reveal that such diagnostics can improve future atmospheric models.

中文翻译：

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从参宿四大气中探测里德伯线

首次在靠近参宿四表面的区域检测到里德堡跃迁的发射线。 H30α在 231.905 GHz 观测到线，半高宽 ~42 km s ^-1且翼延伸。 232.025 GHz（FWHM ∼21 km s ^-1 ）的第二条线被建模为丰富的低第一电离势金属的里德堡跃迁的组合。两款H30α和 Rydberg 联合生产线 X30α由 Voigt 剖面拟合，电子碰撞展宽可能是洛伦兹贡献的部分原因，表明电子密度为几个 10 ⁸ cm ^-3。 X30α位于投影半径为0.9×光学光球半径的相对光滑的环中右 _⋆ , 而 H30α更加块状，在 ∼1.4 处达到峰值右 _⋆。我们使用参宿四的半经验热力学大气模型来计算 232 GHz（1.29 毫米）连续谱和线剖面，并做出简单的假设。光离子化的丰富金属在电子密度中占主导地位，并且预测的 232 GHz 连续光深度统一表面出现在 ∼1.3右 _⋆，与观察结果非常一致。假设 Mg、Si 和 Fe 的水平总体服从 Saha-Boltzmann 分布，模型预测 X30α发射发生在温度和湍流呈放射状升高的区域。纳入电离 C 和非 LTE 效应可能会改变积分通量和发射位置。这些模拟证实了观测到的参宿四的里德伯转变线的身份，并揭示了这种诊断可以改进未来的大气模型。