LTD064402+245919: A Subgiant with a 1–3 M ⊙ Undetected Companion Identified from LAMOST-TD Data
LTD064402+245919: A Subgiant with a 1–3 M ⊙ Undetected Companion Identified from LAMOST-TD Data
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DOI：
10.3847/1538-4357/ac31b3
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发表时间：
2021-10
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影响因子：
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通讯作者：
F. Yang;Bo Zhang;R. J. Long;Youjun Lu;S. Shan;Xing Wei;J. Fu;Xian-fei Zhang;Zhi-Chao Zhao-Zhi-Chao-Z
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作者：
F. Yang;Bo Zhang;R. J. Long;Youjun Lu;S. Shan;Xing Wei;J. Fu;Xian-fei Zhang;Zhi-Chao Zhao-Zhi-Chao-Z
单线光谱双星最近对恒星质量黑洞的发现做出了贡献，独立于x射线瞬变方法。我们发现了一个单线双星系统，LTD064402+245919，其轨道周期为14.50天。观测到的成分是一个亚巨星，质量为2.77±0.68 M⊙，半径为15.5±2.5 R⊙，有效温度为4500±200 K，表面重力对数g为2.5±0.25指数。这一发现利用了大空域多目标光纤光谱望远镜的时域观测和兹威基瞬态观测。我们的通用软件管道应用Lomb-Scargle周期图来确定轨道周期，并使用机器学习从折叠的光曲线中对变量类型进行分类。考虑到主星质量、质量函数和次光度探测极限的限制，我们采用一个组合模型从光速度曲线和径向速度曲线估计轨道参数。在未设置未检测组分类型时，得到径向速度半幅值为44.6±1.5 km s−1，质量比为0.73±0.07，未检测组分质量为2.02±0.49 M⊙。我们得出的结论是，当未检测到的分量被建模为致密物体时，倾角没有得到很好的约束，次级质量大于1 M⊙。根据我们使用蒙特卡罗马尔可夫链模拟的调查，将光谱信噪比增加3倍将使次要光能够被区分（如果存在）。本工作中的算法和软件可以作为识别在x射线中静止的致密物体的通用工具。
Single-line spectroscopic binaries have recently contributed to stellar-mass black hole discovery, independently of the X-ray transient method. We report the identification of a single-line binary system, LTD064402+245919, with an orbital period of 14.50 days. The observed component is a subgiant with a mass of 2.77 ± 0.68 M ⊙, radius 15.5 ± 2.5 R ⊙, effective temperature T eff 4500 ± 200 K, and surface gravity log g 2.5 ± 0.25 dex. The discovery makes use of the Large Sky Area Multi-Object fiber Spectroscopic Telescope time-domain and Zwicky Transient Facility survey. Our general-purpose software pipeline applies a Lomb–Scargle periodogram to determine the orbital period and uses machine learning to classify the variable type from the folded light curves. We apply a combined model to estimate the orbital parameters from both the light and radial velocity curves, taking constraints on the primary star mass, mass function, and detection limit of secondary luminosity into consideration. We obtain a radial velocity semiamplitude of 44.6 ± 1.5 km s−1, mass ratio of 0.73 ± 0.07, and an undetected component mass of 2.02 ± 0.49 M ⊙ when the type of the undetected component is not set. We conclude that the inclination is not well constrained, and that the secondary mass is larger than 1 M ⊙ when the undetected component is modeled as a compact object. According to our investigations using a Monte Carlo Markov Chain simulation, increasing the spectra signal-to-noise ratio by a factor of 3 would enable the secondary light to be distinguished (if present). The algorithm and software in this work are able to serve as general-purpose tools for the identification of compact objects quiescent in X-rays.