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Compact object candidates with K/M-dwarf companions from LAMOST low-resolution survey

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Science China(Physics,Mechanics & Astronomy) 2022年第2期65卷 114-123页

作者： Hui-Jun Mu Wei-Min Gu Tuan Yi Ling-Lin Zheng Hao Sou zhong-rui bai Hao-Tong Zhang Ya-Juan Lei Cheng-Ming Li International Laboratory for Quantum Functional Materials of Henan and School of Physics and MicroelectronicsZhengzhou UniversityZhengzhou 450001China Department of Astronomy Xiamen UniversityXiamen 36 J005Chino CAS Key Laboratory for Research in Gakvdes and Cosmology Department of AstronomyUniversity of Science and Technology of ChinaHefei 230026China National Astronomical Obsen'atories Chinese Academy of SciencesBeijing 100012China

Searching for compact objects(black holes,neutron stars,or white dwarfs)in the Milky Way is essential for understanding the stellar evolution history,the physics of compact objects,and the structure of our *** objects in binaries with a luminous stellar companion are perfect targets for optical *** compact objects can be achieved by monitoring the radial velocities of the companion ***,most of the spectroscopic telescopes usually obtain stellar spectra at a relatively low efficiency,which makes a sky survey for millions of stars practically *** efficiency of a large-scale spectroscopic survey,the Large Sky Area Multi-Object Fiber Spectroscopy Telescope(LAMOST),presents a specific opportunity to search for compact object candidates,i.e.,simply from the spectroscopic ***-type K/M stars are the most abundant populations in our *** to the relatively large Keplerian velocities in the close binaries with a K/M-dwarf companion,a hidden compact object could be discovered and followed-up more *** this study,compact object candidates with K/Mdwarf companions are investigated with the LAMOST low-resolution stellar *** on the LAMOST Data Release 5,we obtained a sample of 56 binaries,each containing a K/M-dwarf with a large radial velocity variation △VR>150 km s^(-1).Complemented with the photometric information from the Transiting Exoplanet Survey Satellite,we derived a sample of 35 compact object candidates,among which,the orbital periods of 16 sources were revealed by the light *** two sources as examples,we confirmed that a compact object existed in the two systems by fitting the radial velocity *** study demonstrates the principle and the power of searching for compact objects through LAMOST.

关键词： spectroscopic binaries binary stars close binaries radial velocities stellar dynamics and kinematics

Kinematics and stellar population properties of the Andromeda galaxy by using the spectroscopic observations of the Guoshoujing Telescope

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Research in Astronomy and Astrophysics 2011年第9期11卷 1093-1110页

作者： Hu ZOU Yan-Bin Yang Tian-Meng Zhang Jun Ma Xu Zhou Ali Luo Hao-Tong Zhang zhong-rui bai Yong-Heng Zhao National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China Graduate University of Chinese Academy of Sciences Beijing 100049 China

The Andromeda galaxy was observed by the Guoshoujing Telescope （formerly named the Large Sky Area Multi-Object Fiber Spectroscopic Telescope -- LAMOST）, during the 2009 commissioning phase. Due to the absence of standard stars for flux calibration, we use the photometric data of 15 intermediate bands in the Beijing-Arizona-Taipei-Connecticut （BATC） survey to calibrate the spectra. In to- tal, 59 spectra located in the bulge and disk of the galaxy are obtained. Kinematic and stellar population properties of the stellar content are derived with these spectra. We obtain the global velocity field and calculate corresponding rotation velocities out to about 7 kpc along the major axis. These rotation velocity measurements comple- ment those of the gas content, such as the H I and CO. The radial velocity dispersion shows that the stars in the bulge are more dynamically thermal and the disk is more rotationally-supported. The age distribution shows that the bulge was formed about 12 Gyr ago, the disk is relatively younger and the ages of some regions along the spi- ral arms can reach as young as about 1 Gyr. These young stellar populations have a relatively richer abundance and larger reddening. The overall average metallicity of the galaxy approximates the solar metallicity and a very weak abundance gradient is gained. The reddening map gives a picture of a dust-free bulge and a distinct dusty ring in the disk.

关键词： methods: data analysis -- techniques: spectroscopic -- galaxies: indi- vidual (M31) -- galaxies: stellar content

Moon night sky brightness simulation for the Xinglong station

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Research in Astronomy and Astrophysics 2013年第10期13卷 1255-1268页

作者： Song Yao Hao-Tong Zhang Hai-Long Yuan Yong-Heng Zhao Yi-Qiao Dong zhong-rui bai Li-Cai Deng Ya-Juan Lei Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Graduate University of Chinese Academy of Sciences

Using a sky brightness monitor at the Xinglong station of National Astronomical Observatories,Chinese Academy of Sciences,we collected data from22 dark clear nights and 90 moon *** first measured the sky brightness variation with time for dark nights and found a clear correlation between sky brightness and human *** with a modified sky brightness model of moon nights and data from these nights,we derived the typical value for several important parameters in the *** these results,we calculated the sky brightness distribution under a given moon condition for the Xinglong ***,we simulated the sky brightness distribution of a moon night for a telescope with a 5 field of view（such as LAMOST）.These simulations will be helpful for determining the limiting magnitude and exposure time,as well as planning the survey for LAMOST during moon nights.

关键词： Moon scattering site testing telescopes

X-ray activity from different types of stars

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Research in Astronomy and Astrophysics 2019年第7期19卷 87-102页

作者： Lin He Song Wang Xiao-Jie Xu Roberto Soria Ji-Feng Liu Xiang-Dong Li Yu bai zhong-rui bai Jin-Cheng Guo Yan-Li Qiu Yong Zhang Ruo-Chuan Xu Ke-Cheng Qian School of Astronomy and Space Science and Key Laboratory of Modern Astronomy and Astrophysics Nanjing UniversityNanjing 210093China United World College Changshu 215500China Key Laboratory of Optical Astronomy National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China College of Astronomy and Space Sciences University of Chinese Academy of SciencesBeijing 100049China International Centre for Radio Astronomy Research Curtin UniversityGPO Box U1987PerthWA 6845Australia Sydney Institute for Astronomy School of Physics A2& The University of SydneySydneyNSW 2006Australia WHU-NAOC Joint Center for Astronomy Wuhan UniversityWuhan 430072China Department of Astronomy Peking UniversityBeijing 100871China Nanjing Inst让ute of Astronomical Optics & Technology National Astronomical ObservatoriesChinese Academy of SciencesNanjing 210042China International Department the Affiliated High School of SCNUGuangzhou 510630China

X-ray emission is an important indicator of stellar *** this paper,we study stellar Xray activity using the XMM-Newton and LAMOST data for different types of *** provide a sample including 1259 X-ray-emitting stars,of which 1090 have accurate stellar parameter *** sample size is much larger than those used in previous *** find a bimodal distribution of the X-ray to optical flux ratio(log(fX/fV)) for G and K *** interpret that this bimodality is due to two subpopulations with different coronal heating ***,using the full widths at half maxima calculated from Hα and Hβ lines,we show that these stars in the inactive peaks have smaller rotational *** is consistent with the magnetic dynamo theory that presumes stars with low rotational velocities have low levels of stellar *** also examine the correlation between log(fX/fV) and luminosity of the excess emission in the Hα line,and find a tight relation between the coronal and chromospheric activity indicators.

关键词： X-rays stars-stars activity-stars late-type

Relative flux calibration for the Guoshoujing Telescope (LAMOST)

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Research in Astronomy and Astrophysics 2012年第4期12卷 453-464页

作者： Yi-Han Song A-Li Luo Georges Comte zhong-rui bai Jian-Nan Zhang Wei Du Hao-Tong Zhang Jian-Jun Chen Fang Zuo Yong-Heng Zhao National Astronomical Observatories Chinese Academy of SciencesBeijing 100012China Key Laboratory of Optical Astronomy National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100012China Graduate University of Chinese Academy of Sciences Beijing 100049China Observatoire Astronomique Marseille-Provence and Laboratoire d'Astrophysique de Marseille F-13388 Marseille CedexFrance

This paper presents a relative flux calibration method for the Guoshoujing Telescope （LAMOST）, which may be applied to connect a blue spectrum to a red spectrum to build the whole spectrum across the total wavelength range （3700 ～ 9000 A）. In each spectrograph, we estimate the effective temperatures of selected stars using a grid of spectral line indices in the blue spectral range and a comparison with stellar atmosphere models. For each spectrograph, stars of types A and F are selected as pseudo-standard stars, and the theoretical spectra are used to calibrate both the blue （3700 ～ 5900 A） and red spectrograph arms （5700 ～ 9000 A）. Then the spectral response function for these pseudo-standard stars could be used to correct the raw spectra provided by the other fibers of the spectrograph, after a fiber efficiency function has been derived from twilight flat-field exposures. A key problem in this method is the fitting of a pseudo stellar continuum, so we also give a detailed description of this step. The method is tested by comparing a small sample of LAMOST spectra calibrated in this way on stars also observed by the Sloan Digital Sky Survey. The result shows that the T eff estimation and relative flux calibration method are adequate.

关键词： techniques: spectroscopic — calibration: methods:data analysis

LAMOST medium-resolution spectral survey of Galactic nebulae(LAMOST-MRS-N):subtraction of geocoronal Hαemission

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Research in Astronomy and Astrophysics 2021年第11期21卷 89-97页

作者： Wei Zhang Hong Wu Chao-Jian Wu Juan-Juan Ren Jian-Jun Chen Chih-Hao Hsia Yu-zhong Wu Hui Zhu Jian-Rong Shi zhong-rui bai Zhao-Xiang Qi Yong-Heng Zhao Yong-Hui Hou CAS Key Laboratory of Optical Astronomy National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China CAS Key Laboratory of Space Astronomy and Technology National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China State Key Laboratory of Lunar and Planetary Sciences Macao University of Science and TechnologyTaipaMacaoChina Shanghai Astronomical Observatory Chinese Academy of SciencesShanghai 200030China Nanjing Institute of Astronomical Optics&Technology National Astronomical ObservatoriesChinese Academy of SciencesNanjing 210042China School of Astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049China

We introduce a method of subtracting geocoronal Hαemissions from the spectra of LAMOST medium-resolution spectral survey of Galactic nebulae(LAMOST-MRS-N).The flux ratios of the Hαsky line to the adjacent OHλ6554 single line do not show a pattern or gradient distribution in a *** interestingly,the ratio is well correlated to solar altitude,which is the angle of the Sun relative to the Earth’s *** is found that the ratio decreases from 0.8 to 0.2 with the decreasing solar altitude from–17 to–73 *** on this relation,which is described by a linear function,we can construct the Hαsky component and subtract it from the science *** method has been applied to the LAMOST-MRSN data,and the contamination level of the Hαsky to nebula is reduced from 40%to less than 10%.The new generated spectra will significantly improve the accuracy of the classifications and the measurements of physical parameters of Galactic nebulae.

关键词： techniques:spectroscopic instrumentation:spectrographs ISM:general

Sky subtraction for LAMOST

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Research in Astronomy and Astrophysics 2017年第9期17卷 25-38页

作者： zhong-rui bai Hao-Tong Zhang Hai-Long Yuan Guang-Wei Li Jian-Jun Chen Ya-Juan Lei Hui-Qin Yang Yi-Qiao Dong Gang Wang Yong-Heng Zhao 1 University of Chinese Academy of Sciences Beijing 100049China Key Lab for Optical Astronomy National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100012China

Sky subtraction is a key technique in data reduction of multi-fiber spectra. Knowledge of characteristics related to the instrument is necessary to determine the method adopted in sky subtraction. In this study, we describe the sky subtraction method designed for the Large sky Area Multi-Object fiber Spectroscopic Telescope （LAMOST） survey. The method has been integrated into the LAMOST 2D Pipeline v2.6 and applied to data from LAMOST DR3 and later. For LAMOST, calibration using sky emission lines is used to alleviate the position-dependent （and thus time-dependent） ,-~ 4% fiber throughput uncertainty and small wavelength instability （0.1/~） during observation. Sky subtraction using principal component analysis （PCA） further reduces 25% of the sky line residual from OH fines in the red part of LAMOST spectra after the master sky spectrum, which is derived from a B-spline fit of 20 sky fibers in each spectrograph. Using this approach, values are adjusted by a sky emission line and subtracted from each fiber. Further analysis shows that our wavelength calibration accuracy is about 4.5 km s-1, and the averages of residuals after sky subtraction are about 3% for sky emission lines and 3% for the continuum region. The relative sky subtraction residuals vary with moonlight background brightness, and can reach as low as 1.5% for regions that have sky emission lines during a dark night. Tests on F stars with both similar sky emission line strength and similar object continuum intensity show that the sky emission line residual of LAMOST is smaller than that of the SDSS survey.

关键词： techniques: spectroscopic -- methods data analysis -- instrumentation spectrographs

On the radial velocity calibrations in the LAMOST medium-resolution spectroscopic survey of nebulae

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Research in Astronomy and Astrophysics 2021年第3期21卷 1-14页

作者： Juan-Juan Ren Hong Wu Chao-Jian Wu Wei Zhang Jian-Jun Chen Chih-Hao Hsia Fan Yang Chao Liu Jian-Rong Shi Yu-zhong Wu Hui Zhu Bin Li zhong-rui bai Hao Tian Yong-Hui Hou CAS Key Laboratory of Space Astronomy and Technology National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China CAS Key Laboratory of Optical Astronomy National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China State Key Laboratory of Lunar and Planetary Sciences Macao University of Science and TechnologyTaipaMacaoChina University of Chinese Academy of Sciences Beijing 100049China Purple Mountain Observatory Chinese Academy of SciencesNanjing 210008China University of Science and Technology of China Hefei 230026China Nanjing Institute of Astronomical Optics&Technology National Astronomical ObservatoriesChinese Academy of SciencesNanjing 210042China School of Astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049China

Accurate radial velocity determinations of optical emission lines(i.e.,[NⅡ]λλ6548,6584,Hαand[SⅡ]λλ6717,6731)are very important for investigating the kinematic and dynamic properties of *** second stage survey program of Large sky Area Multi-Object fiber Spectroscopic Telescope(LAMOST)has started a sub-survey of nebulae(MRS-N)which will spectroscopically observe the optical emission lines of a large sample of nebulae near the Galactic *** now,15 MRS-N plates have been observed from September 2017 to June *** on fitting the sky emission lines in the red band spectra of MRS-N,we investigate the precision of wavelength calibration and find there are systematic deviations of radial velocities(RVs)from~0.2 to 4 km s^(-1) for different *** for the plates obtained in March 2018,the systematic deviations of RVs can be as large as~4 km s^(-1),which then go down to~0.2-0.5 kms^(-1) at the end of 2018 and January *** RV calibration function is proposed for these MRS-N plates,which can simultaneously and successfully calibrate the systematic deviations and improve the precision of RVs.

关键词： ISM:general ISM:kinematics and dynamics technique:spectroscopic technique:radial velocities

Study of the pressure transient behavior of directional wells considering the effect of non-uniform flux distribution

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Petroleum Science 2024年第3期21卷 1765-1779页

作者： Yan-zhong Liang bai-Lu Teng Wan-Jing Luo School of Energy Resources China University of Geosciences(Beijing)Beijing100083China

During the production,the fluid in the vicinity of the directional well enters the wellbore with different rates,leading to non-uniform flux distribution along the directional ***,in all existing studies,it is oversimplified to a uniform flux distribution,which can result in inaccurate results for field ***,this paper proposes a semi-analytical model of a directional well based on the assumption of non-uniform flux ***,the direction well is discretized into a carefully chosen series of linear sources,such that the complex well trajectory can be captured and the nonuniform flux distribution along the wellbore can be considered to model the three-dimensional flow *** using the finite difference method,we can obtain the numerical solutions of the transient flow within the *** the aid of Green's function method,we can obtain the analytical solutions of the transient flow from the matrix to the *** complete flow behavior of a directional well is perfectly represented by coupling the above two types of transient ***,on the basis of the proposed model,we conduct a comprehensive analysis of the pressure transient behavior of a directional *** computation results show that the flux variation along the direction well has a significant effect on pressure *** addition,the directional well in an infinite reservoir may exhibit the following flow regimes:wellbore afterflow,transition flow,inclined radial flow,elliptical flow,horizontal linear flow,and horizontal radial *** horizontal linear flow can be observed only if the formation thickness is much smaller than the well ***,a dip region that appears on the pressure derivative curve indicates the three-dimensional flow behavior near the wellbore.

关键词： Directional well Pressure transient behavior Semi-analytical model Non-uniform flux