分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) started median-resolution spectroscopic (MRS, R$\sim$7500) survey since October 2018. The main scientific goals of MRS, including binary stars, pulsators, and other variable stars are launched with a time-domain spectroscopic survey. However, the systematic errors, including the bias induced from wavelength calibration and the systematic difference between different spectrographs have to be carefully considered during radial velocity measurement. In this work, we provide a technique to correct the systematics in the wavelength calibration based on the relative radial velocity measurements from LAMOST MRS spectra. We show that, for the stars with multi-epoch spectra, the systematic bias which is induced from the exposures of different nights can be well corrected for LAMOST MRS in each spectrograph. And the precision of radial velocity zero-point of multi-epoch time-domain observations reaches below 0.5 km/s . As a by-product, we also give the constant star candidates, which can be the secondary radial-velocity standard star candidates of LAMOST MRS time-domain surveys.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Jianping Xiong
Chao Liu
Jiao Li
Jiadong Li
Bo Zhang
Xiaodian Chen
Changqing Luo
Zihuang Cao
Yongheng Zhao
摘要： High-precision stellar mass and radius measured directly from binaries can effectively calibrate the stellar models. However, such a database containing full spectral types and large range of metallicity is still not fully established. A continuous effort of data collecting and analysis are requested to complete the database. In this work, we provide a catalog containing 184 binaries with independent atmospheric parameters and accurate masses and radii as the benchmark of stellar mass and radius. The catalog contains 56 new detached binaries from LAMOST Medium-resolution spectroscopic (MRS) survey and 128 detached eclipsing binaries compiled from previous studies. We obtain the orbital solutions of the new detached binaries with uncertainties of masses and radii smaller than 5%. These new samples densify the distribution of metallicity of the high-precision stellar mass library and add 9 hot stars with Teff>8000 K. Comparisons show that these samples well agree with the PARSEC isochrones in Teff-logg-mass-radius-luminosity space. We compare mass and radius estimates from isochrone and SED fitting, respectively, with those from the binary orbital solution. We find that the precision of the stellar-model dependent mass estimates is >10% and the precision of the radius estimates based on atmospheric parameters is >15%. These give a general view of the uncertainty of the usual approaches to estimate stellar mass and radius.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Jianping Xiong
Chao Liu
Jiao Li
Jiadong Li
Bo Zhang
Xiaodian Chen
Changqing Luo
Zihuang Cao
Yongheng Zhao
摘要： High-precision stellar mass and radius measured directly from binaries can effectively calibrate the stellar models. However, such a database containing full spectral types and large range of metallicity is still not fully established. A continuous effort of data collecting and analysis are requested to complete the database. In this work, we provide a catalog containing 184 binaries with independent atmospheric parameters and accurate masses and radii as the benchmark of stellar mass and radius. The catalog contains 56 new detached binaries from LAMOST Medium-resolution spectroscopic (MRS) survey and 128 detached eclipsing binaries compiled from previous studies. We obtain the orbital solutions of the new detached binaries with uncertainties of masses and radii smaller than 5%. These new samples densify the distribution of metallicity of the high-precision stellar mass library and add 9 hot stars with Teff>8000 K. Comparisons show that these samples well agree with the PARSEC isochrones in Teff-logg-mass-radius-luminosity space. We compare mass and radius estimates from isochrone and SED fitting, respectively, with those from the binary orbital solution. We find that the precision of the stellar-model dependent mass estimates is >10% and the precision of the radius estimates based on atmospheric parameters is >15%. These give a general view of the uncertainty of the usual approaches to estimate stellar mass and radius.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Yanjun Guo
Jiao Li
Jianping Xiong
Jiangdan Li
Luqian Wang
Heran Xiong
Feng Luo
Yonghui Hou
Chao Liu
Zhanwen Han
Xuefei Chen
摘要： Massive binaries play significant roles in many fields. Identification of massive stars, particularly massive binaries, is of great importance. In this paper, by adopting the technique of measuring the equivalent widths of several spectral lines, we identified 9,382 early-type stars from LAMOST medium-resolution survey and divided the sample into four groups, T1 ($\sim$O-B4), T2 ($\sim$B5), T3 ($\sim$B7), and T4 ($\sim$B8-A). The relative radial velocities $RV_{\rm rel}$ were calculated using the Maximum Likelihood Estimation. The stars with significant changes of $RV_{\rm rel}$ and at least larger than 15.57km s$^{-1}$ were identified as spectroscopic binaries. We found that the observed spectroscopic binary fractions for the four groups are $24.6\%\pm0.5\%$, $20.8\%\pm0.6\%$, $13.7\%\pm0.3\%$, and $7.4\%\pm0.3\%$, respectively. Assuming that orbital period ($P$) and mass ratio ($q$) have intrinsic distributions as $f(P) \propto P^\pi$ (1\textless$P$\textless1000 days) and $f(q) \propto q^\kappa$ (0.1\textless$q$\textless1), respectively, we conducted a series of Monte-Carlo simulations to correct observational biases for estimating the intrinsic multiplicity properties. The results show that the intrinsic binary fractions for the four groups are 68$\%\pm8\%$, 52$\%\pm3\%$, 44$\%\pm6\%$, and 44$\%\pm6\%$, respectively. The best estimated values for $\pi$ are -1$\pm0.1$, -1.1$\pm0.05$, -1.1$\pm0.1$, and -0.6$\pm0.05$, respectively. The $\kappa$ cannot be constrained for groups T1 and T2 and is -2.4$\pm0.3$ for group T3 and -1.6$\pm0.3$ for group T4. We confirmed the relationship of a decreasing trend in binary fractions towards late-type stars. No correlation between the spectral type and the orbital period distribution has been found yet, possibly due to the limitation of observational cadence.
点击量
待评议
点击量
下载量
评论
