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On the Identification of N-rich Metal-poor Field Stars with Future Chinese Space Station Telescope

Research in Astronomy and Astrophysics 2024年第1期24卷 151-164页

作者： Jiajun Zhang Baitian Tang Jiang Chang Xiangxiang Xue JoséGFernández-Trincado Chengyuan Li Long Wang Hao Tian Yang Huang School of Physics and Astronomy Sun Yat-sen UniversityZhuhai 519082China CSST Science Center for the Guangdong-Hong Kong-Macao Greater Bay Area Sun Yat-sen UniversityZhuhai 519082China Purple Mountain Observatory Chinese Academy of SciencesNanjing 210034China Key Lab of Optical Astronomy National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China Instituto de Astronomía Universidad Católica del NorteAv.Angamos 0610AntofagastaChile Key Lab of Space Astronomy and Technology National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China School of Astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049China

During the long term evolution of globular clusters(GCs), some member stars are lost to the field. The recently found nitrogen-rich(N-rich) metal-poor field stars are promising candidates of these GC escapees, since N enhancement is the fingerprint of chemically enhanced populations in GCs. In this work, we discuss the possibility of identifying N-rich metal-poor field stars with the upcoming Chinese Space Station Telescope(CSST). We focus on the main survey camera with NUV, u, g, r, i, z, y filters and slitless spectrograph with a resolution about 200.The combination of UV sensitive equipment and prominent N-related molecular lines in the UV band bodes well for the identification: the color–color diagram of(u-g) versus(g-r) is capable of separating N-rich field stars from normal halo stars, if metallicity can be estimated without using the information on u-band photometry.Besides, the synthetic spectra show that a signal-to-noise ratio of 10 is sufficient to identify N-rich field stars. In the near future, a large sample of N-rich field stars found by CSST, combined with state-of-the-art N-body simulations will be crucial to deciphering GC-Galaxy co-evolution.

关键词： stars:chemically peculiar stars:abundances techniques:photometric techniques:spectroscopic

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A 3 Giga Sample Per Second 14-bit Digital Receiver with 9 GHz Input Bandwidth for Solar Radio Observation

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Research in Astronomy and Astrophysics 2022年第8期22卷 159-169页

作者：张园园张磊尚自乾路光武昭苏艳蕊陈耀严发宝 Laboratory for ElectromAgnetic Detection(LEAD) Institute of Space SciencesShandong UniversityWeihai 264209China School of Mechanical Electrical&Information EngineeringShandong UniversityWeihai 264209China

A new digital receiver with excellent performances has been designed and developed for solar radio observation,which can receive the radio signal from direct current(DC)to 9 GHz in the direct acquisition way.On the digital receiver,the analog-to-digital converter(ADC)with 14-bit,two input channels and 3 Giga Samples per second(Gsps)are used to acquire observed signal,and the field-programmable-gate-array chip XCKU115 acts as the processing module.The new digital receiver can be used to directly sample the solar radio signals of frequency under 9 GHz.When receiving the solar radio signal above 9 GHz,the new digital receiver can save 1–2 stages of frequency down-conversion,and effectively improve many indexes of the solar radio observation system,i.e.,the time resolution,analog front-end circuit,weight and volume of the analog circuit system.Compared with the digital receiver with sampling rate below 1 Gsps used in existing solar radio telescope,the new digital receiver reduces the frequency switching times of large bandwidth,which is beneficial to improving the frequency and time resolutions.The ADC sampling resolution of 14 bits,providing a large dynamic range,is very beneficial to observing smaller solar eruptions.This receiver,which would be used in the solar radio observation system,well meets the latest requirements with the resolutions of time(≤1 ms)and frequency(≤0.5 MHz)for fine observation of radio signals.

关键词： instrumentation:spectrographs techniques:spectroscopic techniques:radar astronomy

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Mapping of Compositional Diversity and Chronological Ages of Lunar Farside Multiring Mare Moscoviense Basin:Implications to the Middle Imbrian Mare Basalts

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Research in Astronomy and Astrophysics 2022年第12期22卷 130-151页

作者： A.Karthi S.Arivazhagan Manish Sharma Centre for Applied Geology The Gandhigram Rural Institute—Deemed to be UniversityGandhigramDindigul-624302Tamil NaduIndia College of Natural and Health Sciences Zayed UniversityP.O.Box 144534Abu DhabiUnited Arab Emirates

The Mare Moscoviense is an astonishing rare flatland multi-ring basin and one of the recognizable mare regions on the Moon's farside.The mineralogical,chronological,topographical and morphological studies of the maria surface of the Moon provide a primary understanding of the origin and evolution of the mare provinces.In this study,the Chandrayaan-1 M^(3)data have been employed to prepare optical maturity index,FeO and TiO^(2)concentration,and standard band ratio map to detect the mafic indexes like olivine and pyroxene minerals.The crater size frequency distribution method has been applied to LROC WAC data to obtain the absolute model ages of the Moscoviense basin.The four geological unit ages were observed as 3.57 Ga(U-2),3.65 Ga(U-1),3.8 Ga(U-3)and 3.92 Ga(U-4),which could have been formed between the Imbrian and Nectarian epochs.The M^(3)imaging and reflectance spectral parameters were used to reveal the minerals like pyroxene,olivine,ilmenite,plagioclase,orthopyroxene-olivine-spinel lithology,and olivine-pyroxene mixtures present in the gabbroic basalt,anorthositic and massive ilmenite rocks,and validated with the existing database.The results show that the Moscoviense basin is dominated by intermediate TiO^(2)basalts that derived from olivine-ilmenite-pyroxene cumulate depths ranging from 200 to 500 km between 3.5 Ga and 3.6 Ga.

关键词： astrobiology molecular processes methods:data analysis techniques:image processing techniques:imaging spectroscopy techniques:spectroscopic planets and satellites:composition planets and satellites:surfaces planets and satellites:terrestrial planets

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Photometric and spectroscopic Analysis of LBV Candidate J004341.84+411112.0 in M31

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Research in Astronomy and Astrophysics 2022年第1期22卷 237-244页

作者： A.Sarkisyan Sholukhova Fabrika A.Valeev A.Valcheva P.Nedialkov A.Tatamikov Special Astrophysical Observatory of Russian Academy of Sciences Niznij Arkhyz 369167Karachai-CherkessiaRussia Crimean Astrophysical Observatory Russian Academy of SciencesNauchnyi 298409Russia Department of Astronomy Sofia University5 J.Bourchier BlvdSofia 1164Bulgaria Sternberg Astronomical Institute Moscow M.V.Lomonosov State UniversityUniversitetskiy Prospekt 13Moscow 119234Russia

We study Luminous Blue Variable(LBV)candidate J004341.84+411112.0 in the Andromeda galaxy.We present optical spectra of the object obtained with the 6 m telescope of BTA SAO RAS.The candidate shows typical LBV features in its spectra:broad and strong hydrogen lines and the He I lines with P Cygni profiles.Its remarkable spectral resemblance to the well known LBV P Cygni suggests a common nature of the objects and supports LBV classification of J004341.84+411112.0.We estimate the temperature,reddening,radius and luminosity of the star using its spectral energy distribution.Obtained bolometric luminosity of the candidate(M_(bol)=-10.41±0.12 mag)is quite similar to those of known LBV stars in the Andromeda galaxy.We analyzed a ten year light curve of the object in R filter.The candidate demonstrates photometric variations of the order of 0.4 mag,with an overall brightness increasing trendΔR>0.1 mag.Therewith,the corresponding color variations of the object are fully consistent with LBV behavior when a star become cooler and brighter in the optical spectral range with a nearly constant bolometric luminosity.LBV-type variability of the object,similarity of its spectrum and estimated luminosity to those of known LBVs allow us to classify J004341.84+411112.0 as an LBV.

关键词： stars:early-type stars:massive stars:variables:S Doradus stars:Wolf Rayet techniques:photometric techniques:spectroscopic galaxies:individual(KIC 8098300)

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A Baseline Correction Algorithm for FAST

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Research in Astronomy and Astrophysics 2022年第8期22卷 1-5页

作者： De-Jian Liu Ye Xu Ying-Jie Li Ze-Hao Lin Shuai-Bo Bian Chao-Jie Hao Purple Mountain Observatory Chinese Academy of SciencesNanjing 210008China School of Astronomy and Space Science University of Science and Technology of ChinaHefei 230026China

The Five-hundred-meter Aperture Spherical radio Telescope(FAST)is the most sensitive ground-based,singledish radio telescope on Earth.However,the original HⅠspectra produced by FAST are affected by standing waves.To maximize the power of FAST for high-sensitivity observations,we proposed an algorithm that combines fast Fourier transforms and extreme envelope curves to automatically correct the baselines of FAST HⅠspectra and remove standing waves from the baselines.This algorithm can reduce the amplified noise level caused by standing waves to a near-ideal level without losing signals or introducing false signals.The root mean square of the average baseline reaches~8 mK,approaching the theoretical sensitivity of an HⅠspectrum produced by FAST for an integration time of 335 minutes,i.e.,~6 m K.

关键词： methods:observational techniques:spectroscopic telescopes

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Speckle-interferometric Study of Close Visual Binary System HIP 11253(HD 14874)using Gaia(DR2 and EDR3)

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Research in Astronomy and Astrophysics 2023年第7期23卷 221-228页

作者： Hussam Aljboor Ali Taani Department of Basic Scientific Sciences Prince Hussein Bin Abdullah Ⅱ Academy for Civil ProtectionAl Balqa Applied UniversityAmmanJordan Physics Department Faculty of ScienceAl Balqa Applied University19117 SaltJordan

We present a comprehensive set of physical and geometrical parameters for each of the components of the close visual binary system HIP 11253(HD 14874).We present an analysis for the binary and multiple stellar systems with the aim to obtain a match between the overall observational spectral energy distribution of the system and the spectral synthesis created from model atmospheres using Al-Wardat's method for analyzing binary and multiple stellar systems.The epoch positions are used to determine the orbital parameters and the total mass.The parameters of both components are derived as:T_(eff)^(a)=6025,T_(eff)^(b)=4710,logg_(a)=4.55,logg_(b)=4.60,R_(a)=1.125 R_(⊙),R_(b)=0.88R_(⊙),L_(a)=1.849 L_(⊙),L_(b)=0.342 L_(⊙).Our analysis shows that the spectral types of the components are F9 and K3.By combining the orbital solution with the parallax measurements of Gaia DR2 and EDR3,we estimate the individual masses using the H-R diagram as M_(a)=1.09 M_(⊙)and M_(b)=0.59 M_(⊙)for using Gaia DR2 parallax and M_(a)=1.10 M_(⊙)and M_(b)=0.61 M_(⊙)for using Gaia EDR3 parallax.Finally,the location of both system's components on the stellar evolutionary tracks is presented.

关键词： (stars:)binaries:visual stars:kinematics and dynamics (stars:)binaries(including multiple):close techniques:interferometric techniques:spectroscopic

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Sodium Abundances in Very Metal-poor Stars

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Research in Astronomy and Astrophysics 2023年第7期23卷 229-246页

作者： Yu-Fu Shen S.A.Alexeeva Gang Zhao Shuai Liu Zeming Zhou Hongliang Yan Haining Li Tianyi Chen Xiaodong Xu Huiling Chen Huawei Zhang Jianrong Shi CAS Key Laboratory of Optical Astronomy National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China School of Astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049China Department of Astronomy School of PhysicsPeking UniversityBeijing 100871China Kavli Institute for Astronomy and Astrophysics Peking UniversityBeijing 100871China

Chemical composition of very metal-poor(VMP)stars can provide observational constraints on current models of nucleosynthesis and the chemical evolution of the Galaxy.It has been found that the scatter of[Na/Fe]versus[Fe/H]in VMP stars is very large in contrast with most other elements.Moreover,a negative slope in[Na/Fe]versus[Fe/H]was found for giants,which is very unlikely according to the theory of nucleosynthesis.For the sample of93 VMP stars in the metallicity range-4.25<[Fe/H]<-1.64 we obtained NLTE sodium abundances using the line profile fitting method by employing accurate atmospheric parameters determined when taking into account NLTE line formation for both FeⅠand FeⅡ.Originally selected from the LAMOST low-resolution spectral database,the spectra of stars were obtained with the High Dispersion Spectrograph of the Subaru Telescope.For 57turn-off stars in metallicity domain-3.04<[Fe/H]<-1.64,we obtained mean[Na/Fe]=-0.29±0.14 and positive slope 0.09±0.06.For 21 giants distributed over metallicity-3.59<[Fe/H]<-2.19,we found mean[Na/Fe]=-0.35±0.1 and positive slope 0.07±0.07.Our[Na/Fe]trend is lower by~0.2 dex,compared to the modern GCE model.We believe the GCE model should be adjusted,by considering the associated scatter.Twelve stars in our sample are found to be outliers,with too low or too high Na abundances.

关键词： techniques:spectroscopic stars:abundances stars:atmospheres

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Spectro-polarimetric observations at the NVST:I.instrumental polarization calibration and primary measurements

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Research in Astronomy and Astrophysics 2020年第4期20卷 7-18页

作者： Jun-Feng Hou Zhi Xu Shu Yuan Yu-Chao Chen Jian-Guo Peng Dong-Guang Wang Jun Xu Yuan-Yong Deng Zhen-Yu Jin Kai-Fan Ji Zhong Liu National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China Yunnan Observatories Chinese Academy of SciencesKunming 650216China

This paper is devoted to the primary spectro-polarimetric observation performed at the New Vacuum Solar Telescope(NVST)of China since 2017,and our aim is to precisely evaluate the real polarimetric accuracy and sensitivity of this polarimetry by using full Stokes spectro-polarimetric observations of the photospheric line Fe I 532.4 nm.In the work,we briefly describe the salient characteristic of the NVST as a polarimeter in terms of technology and then characterize its instrumental polarization based on the operation in 2017 and 2019.It is verified that the calibration method utilizing the instrumental polarization calibration unit(ICU)is stable and credible.The calibration accuracy can reach up to 3×10^-3.Based on the scientific observation of NOAA Active Region 12645 on 2017 April 5,we estimate that the residual cross-talk from Stokes I to Stokes Q,U and V,after the instrumental polarization calibration,is about 4×10^-3 on average,which is consistent with the calibration accuracy and close to the photon noise.The polarimetric sensitivity(i.e.,the detection limit)for polarized light is of the order of 10-3 with an integration time over 20 s.Slow modulation rate is indeed an issue for the present system.The present NVST polarimeter is expected to be integrated with a high-order adaptive optics system and a field scanner to realize 2 D vector magnetic field measurements in the following instrumentation update.

关键词： techniques:polarimetric techniques:spectroscopic Sun:magnetic fields

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A pilot study of catching high-z GRBs and exploring circumburst environment in the forthcoming SVOM era

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Research in Astronomy and Astrophysics 2020年第8期20卷 211-216页

作者： Jing Wang Yu-Lei Qiu Jian-Yan Wei Guangxi Key Laboratory for Relativistic Astrophysics School of Physical Science and TechnologyGuangxi UniversityNanning 530004China Key Laboratory of Space Astronomy and Technology National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China School of Astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049China

Rapid spectroscopy of GRB afterglows is an important and hard task.Based on the archival XSGRB spectral database,we here perform a pilot study on the afterglow's spectroscopy in the forthcoming SVOM era in two aspects.First,our simulation indicates that the color acquired from the SVOM/VT blue and red channels is effective in discriminating between low-z(z≤3)and distant GRB candidates until z^6.Second,by doubling the sample size,we find that the previously proposed global photoionization response of the circumburst gas to the prompt emission(i.e.,the CIV/CII-L(iso)/E2peak relationship)is roughly confirmed.although the confirmation is dissatisfactory at the large L(iso)/E2peak end.We believe that this issue can be further addressed in the SVOM era by a larger spectroscopy sample,thanks to its capability of rapid identification of optical candidates of afterglow and its anti-solar pointing strategy.

关键词： gamma ray bursts:general techniques:photometric techniques:spectroscopic methods:statistical

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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 plate.More interestingly,the ratio is well correlated to solar altitude,which is the angle of the Sun relative to the Earth’s horizon.It is found that the ratio decreases from 0.8 to 0.2 with the decreasing solar altitude from–17 to–73 degree.Based on this relation,which is described by a linear function,we can construct the Hαsky component and subtract it from the science spectrum.This 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

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