标题： A壳星Phi Leo的重新研究：其光球和周围星体光谱 显示英文标题

标题： The A-shell star Phi Leo revisited: its photospheric and circumstellar spectra

摘要： 在朝向A型壳星$\phi$狮子座的Ca ii K线中观测到的红移和蓝移吸收特征，我们在以前的工作中提出可能是由于围绕恒星的固态彗星状天体。 我们的目标是将对这个天体的观测研究扩展到A型光球的其他特征光谱线以及来自其周围壳层的线。 我们获得了从2015年12月到2019年1月在不同望远镜上收集的500多条高分辨率光学光谱。 我们分析了一些光球线，特别是Ca i 4226\AA 和 Mg ii 4481\AA ，以及围绕恒星的壳层线Ca ii H&K、Ca ii IR三重态、Fe ii、Ti ii和巴尔末线H$\alpha$和 H$\beta$。 我们的观测研究表明，$\phi$狮子座是一个变星$\delta$Scuti 星，其光谱显示在光球线轮廓上叠加了显著的突起和凹陷，这些突起和凹陷的强度和锐度变化，从蓝移到更红移的径向速度传播，并持续数小时，可能由非径向脉动产生。 同时，所有壳层线在 $\sim$3 km/s 处呈现出以 CS 特征核心为中心的发射，并且在发射的两侧有两个变化的吸收极小值。 在 Ca ii H&K、Fe ii 和 Ti ii 线中观察到的变化发生在从分钟到天以及观测运行的任何时间尺度上，但不同线之间没有明显的相关性或可识别的时间模式。 在 H$\alpha$的情况下，CS 贡献仅在一次观测运行中是变化的。 我们认为 $\phi$ Leo 是一个快速旋转的 $\delta$ Scuti 星，周围有一个变化的（几乎边缘朝向的）CS 盘，可能由 $\delta$ Scuti 振荡重新补充。 显示英文摘要

摘要： Variable red- and blue-shifted absorption features observed in the Ca ii K line towards the A-type shell star $\phi$ Leo have been suggested by us in a previous work to be likely due to solid, comet-like bodies in the circumstellar (CS) environment. Our aim is to expand our observational study of this object to other characteristic spectral lines of A-type photospheres as well as to lines arising in their CS shells. We have obtained more than 500 high-resolution optical spectra collected at different telescopes from December 2015 to January 2019. We have analysed some photospheric lines, in particular Ca i 4226 \AA ~and Mg ii 4481 \AA, as well as the circumstellar shell lines Ca ii H\&K, Ca ii IR triplet, Fe ii, Ti ii, and the Balmer lines H$\alpha$ and H$\beta$. Our observational study reveals that $\phi$ Leo is a variable $\delta$ Scuti star whose spectra show remarkable dumps and bumps superimposed on the photospheric line profiles, which vary their strength and sharpness, propagate from blue- to more red-shifted radial velocities and persisting during a few hours, likely produced by non-radial pulsations. At the same time, all shell lines present an emission at $\sim$3 km/s centered at the core of the CS features, and two variable absorption minima at both sides of the emission. The variations observed in the Ca ii H\&K, Fe ii and Ti ii lines occur at any time scale from minutes to days and observing run, but without any clear correlation or recognizable temporal pattern among the different lines. In the case of H$\alpha$ the CS contribution is also variable in just one of the observing runs. We suggest that $\phi$ Leo is a rapidly rotating $\delta$ Scuti star surrounded by a variable, (nearly) edge-on CS disk possibly re-supplied by the $\delta$ Scuti pulsations.