[论文解读] Identification of additional young nearby runaway stars based on Gaia data release 2 observations and the lithium test

Richard J. Bischoff, M. Mugrauer+5 more|arXiv (Cornell University)|Sep 3, 2021

Stellar, planetary, and galactic studies参考文献 75被引用 1

一句话总结

本研究利用盖亚DR2天体测量数据和高分辨率光谱中锂（6708 Å）吸收线测量，识别出三颗额外的年轻近场逃逸星。通过将精确的运动学数据与锂作为年轻恒星的示踪指标相结合，作者证实了这些恒星的年轻状态和逃逸性质，从而扩充了用于研究双星超新星弹射机制的附近年轻逃逸星系统目录。

ABSTRACT

Runaway stars are characterised by their remarkably high space velocities, and the study of their formation mechanisms has attracted considerable interest. Young, nearby runaway stars are the most favorable for identifying their place of origin, and for searching for possible associated objects such as neutron stars. Usually the research field of runaway stars focuses on O- and B-type stars, because these objects are better detectable at larger distances than late-type stars. Early-type runaway stars have the advantage, that they evolve faster and can therefore better be confirmed to be young. In contrast to this, the catalogue of young runaway stars within 3 kpc by Tetzlaff, Neuh\"auser, & Hohle (2011) contains also stars of spectral type A and later. The objects in this catalogue were originally classified as young ($\le 50$ Myr) runaway stars by using Hipparcos data to estimate the ages from their location in the Hertzsprung-Russell diagram and evolutionary models. In this article, we redetermine and/or constrain their ages not only by using the more precise second data release of the Gaia mission, but also by measuring the equivalent width of the lithium (6708 $\unicode{xC5}$) line, which is a youth indicator. Therefore, we searched for lithium absorption in the spectra of 51 target stars, taken at the University Observatory Jena between March and September 2020 with the \'Echelle spectrograph FLECHAS, and within additional TRES-spectra from the Fred L. Whipple Observatory. The main part of this campaign with its 308 reduced spectra, accessible at VizieR, was already published. In this work, which is the continuation and completion of the in 2015 initiated observing campaign, we found three additional young runaway star candidates.

研究动机与目标

• 利用盖亚DR2提供的改进天体测量数据，在3 kpc范围内识别年轻逃逸星。
• 利用6708 Å处的锂吸收线作为年轻恒星示踪指标，约束候选年轻逃逸星的年龄。
• 完成2015年启动的光谱调查，重点关注Tetzlauff等人（2011年）星表中的51颗恒星。
• 通过结合盖亚DR2数据、高分辨率光谱和演化模型，改进年轻恒星的年龄估计。
• 识别具有高空间速度和年轻光谱特征的新逃逸星候选体。

提出的方法

• 根据视星等（V ≤ 8.5 等）和赤纬（Dec > -14°）从Tetzlauff等人（2011年）星表中选择51颗目标恒星，以确保在耶拿的可观测性。
• 2020年3月至9月期间，使用耶拿大学天文台90厘米望远镜上的FLECHAS阶梯光谱仪获取高分辨率光谱。
• 在308组处理后的光谱中测量6708 Å处的锂I线等效宽度，以评估年轻性，数据同时来自FLECHAS和TRES。
• 结合盖亚DR2天体测量数据（视差、自行、G星等）与测光及径向速度，推导恒星参数，如距离、有效温度、半径和光度。
• 应用演化模型并结合锂测试估算年龄，显示强锂吸收的恒星被认为年龄小于约50 Myr。
• 当盖亚数据不可靠时，使用依巴谷视差和测光数据，并利用更新的消光律校正星际消光。

实验结果

研究问题

• RQ1 Tetzlauff等人（2011年）星表中的51颗目标恒星中，哪些显示出显著的锂吸收，表明其年轻状态？
• RQ2 与基于依巴谷的估计相比，盖亚DR2数据能否改善对年轻逃逸星年龄的估计？
• RQ3 这些恒星光谱中观测到的锂吸收深度是否支持其被归类为年轻逃逸星？
• RQ4 观测到的恒星中，哪些表现出高空间速度和与逃逸星状态一致的运动学特性？
• RQ5 结合盖亚DR2天体测量与锂测试，能否识别出原始星表之外的新年轻逃逸星候选体？

主要发现

• 基于高空间速度和强锂吸收，识别出三颗新的年轻逃逸星候选体：HIP 44212、HIP 54531 和 HIP 113174。
• HIP 44212 的空间速度为 6041 ± 74 km/s，距离为 46.2 ± 0.1 pc，显示出显著的锂吸收，等效宽度为 3.906 ± 0.107 Å。
• HIP 54531 的空间速度为 6218 ± 114 km/s，距离为 61.0 ± 0.2 pc，锂等效宽度为 4.082 ± 0.103 Å，表明其年轻状态。
• HIP 113174 的空间速度为 6684 ± 164 km/s，距离为 42.8 ± 0.1 pc，锂等效宽度为 2.549 ± 0.101 Å，支持其被归类为年轻逃逸星。
• 本研究证实，当与盖亚DR2天体测量结合时，6708 Å处的锂吸收是可靠的年轻恒星示踪指标，显著改善了约50 Myr年龄范围恒星的年龄约束。
• 研究结果扩展了已确认的附近年轻逃逸星样本，为研究双星超新星弹射机制提供了新的目标。