Context. Non-dusty late-type giants without a corona and large-scale pulsations represent objects that do not fulfil the conditions under which standard mass-loss mechanisms can be applied efficiently. The driving mechanism of their winds is still unknown.
Aims. The main goal of this work is to match the radial velocities of absorbing matter with a depth in the red giant (RG) atmosphere in the S-type symbiotic star EG And.
Methods. We measured fluxes and radial velocities of ten FeI absorption lines from spectroscopic observations with a resolution of ~30 000. At selected orbital phases, we modelled their broadened profiles, including all significant broadening mechanisms.
Results. The selected FeI absorption lines at 5151 - 6469A, originate at a radial distance ~1.03 RG radii from its centre. The corresponding radial velocity is typically ~1 km/s , which represents a few percent of the terminal velocity of the RG wind. The high scatter of the radial velocities of several km/s in the narrow layer of the stellar atmosphere points to the complex nature of the near-surface wind mass flow. The average rotational velocity of 11 km/s implies that the rotation of the donor star can contribute to observed focusing the wind towards the orbital plane. The orbital variability of the absorbed flux indicates the highest column densities of the wind in the area between the binary components, even though the absorbing neutral material is geometrically more extended from the opposite side of the giant. This wind density asymmetry in the orbital plane region can be ascribed to gravitational focusing by the white dwarf companion.
Conclusions. Our results suggest that both gravitational and rotational focusing contribute to the observed enhancement of the RG wind towards the orbital plane, which makes mass transfer by the stellar wind highly efficient.
Mass outflow from the symbiotic binary RS Oph during its 2021 outburst
RS Oph是一颗共生的复发新星，包含一颗在活动期间质量损失严重的大质量白矮星。2021年8月，它经历了自19世纪末以来的第七次光学喷发。这项工作的目标是分析从爆发对象流出的结构。根据观测到的11- 15天的$U$、$B$、$V$、$R_{\rm C}$、$I_{\rm C}$等宽谱测光和高分辨H-$α$波谱，我们得到了系统组分和流出量的一些参数及其在观测过程中的变化。在整个观测过程中，由喷射物质产生并遮蔽系统热成分的暖壳层（假光球层）的有效温度为$T_{eff}=15000\pm1000$ K，星云的电子温度为$T_{e}=17000\pm3000$ K。假光球的有效半径为$R_{ eff}=13.3\pm2.0$ R $_{\odot}$，星云$EM=(9.50\pm0.59) $ 10 $^{61}$ cm $^{-3}$的发射测量值为第11天，$R_{eff}=10.3\pm1.6$ R $_{\odot}$和$EM=(5.60\pm0.35)$ 10 $^{61}$ cm $^{-3}$的发射测量值为第15天。为了提供这种发射测量，爆发物体的辐射热光度必须超过其爱丁顿极限。爆发物体通过风的质量损失率比通过流的质量损失率大得多。总速率（来自风+流）小于$(4-5)$ 10 $^{-5}$（d/1.6kpc）$^{3/2}$ M $_{\odot}$ yr $^{-1}$。这…
