ABSTRACT

This work presents and tests a reliable, but nonetheless fast, method for determining the physical parameters of large stellar samples with moderate-resolution spectra, with extensive host star–exoplanet studies in mind. The proposed strategy complements spectral synthesis for obtaining spectroscopically sensitive parameters (i.e. effective temperature and rotation velocity) through other data to keep less critical quantities fixed. We test this approach on a sample of 25 bright (4–7 mag), cool main-sequence stars, for which rotation periods are known from chromospheric activity monitoring. On the basis of good-quality (signal-to-noise ratio 70–80) Tracking and Imaging Gamma-Ray Experiment–Heidelberg Extended Range Optical Spectrograph (TIGRE–HEROS) spectra with a modest spectral resolving power of R = 21 000, we employ the fast iSpec tool. With gravities calculated and approximate metallicities taken from uvby photometry (Geneva–Copenhagen catalogue), spectral synthesis is focused on refining the crucial effective temperature. Finally, rotational velocities are fitted. However, these suffer from cross-talk with gravity and convective turbulence. We find that prescribing macroscopic turbulent velocities for most stars within 2–3 km s⁻¹ (with 4–6 km s⁻¹ for only our three warmest stars) and microscopic turbulent velocities within 0.7–1.5 km s⁻¹ (turbulence increasing with effective temperature, from under 5000 K to 6300 K) results in a satisfactory match (with residuals of 2.5 km s⁻¹) of the period-related, very small rotation velocities of our sample stars. With this prescription, the fast spectral synthesis method described yields effective temperatures similar to intensive atmospheric modelling of high-resolution spectra.

中文翻译：

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适用于大型恒星样品的快速合成光谱拟合：使用已知旋转的25个明亮恒星进行的关键测试

摘要

这项工作提出并测试了一种可靠但快速的方法，该方法用于确定具有中等分辨率光谱的大型恒星样品的物理参数，同时要考虑到广泛的宿主恒星-系外行星研究。所提出的策略补充了光谱综合，以通过其他数据获得光谱敏感参数（即有效温度和旋转速度），以保持较少的关键量固定。我们在25个明亮（4–7 mag）明亮主序恒星样本上测试了该方法，其色轮活动监测表明了旋转周期。在高质量（信噪比70–80）的基础上，跟踪和成像伽玛射线实验–海德堡扩展光谱仪（TIGRE–HEROS）的光谱，其分辨力为R = 21 000，我们使用了快速的iSpec工具。通过计算重力，并通过紫外光度法（日内瓦-哥本哈根目录）获得近似的金属元素，光谱合成的重点是改善关键的有效温度。最后，拟合旋转速度。然而，它们遭受与重力和对流湍流的串扰。我们发现，规定了2–3 km s ^-1之内的大多数恒星的宏观湍流速度（仅对我们三个最暖的恒星规定了4–6 km s ^-1）和0.7–1.5 km s ^-1之内的微观湍流速度（湍流随有效温度（从5000 K到6300 K）在匹配方面令人满意（残差为2.5 km s ^-1）与我们的样本恒星有关的与周期有关的很小的自转速度。使用此处方，所描述的快速光谱合成方法产生的有效温度类似于高分辨率光谱的密集大气建模。