检索结果-南通市图书馆

Possible Habitats for NH_(3),NH_(2)D,H^(13)CN,HC^(15)N,SO,and C^(18)O in the Initial Conditions of High-mass Star Formation

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2024年第4期24卷 237-252页

作者： Quan-Ling Cui Chuan-Peng Zhang Jun-Jie Wang National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China College of Science Qiqihar UniversityQiqihar 161006China Guizhou Radio Astronomical Observatory Guizhou UniversityGuiyang 550000China

The initial condition of high-mass star formation is a complex area of study because of the high densities(n_(H_(2))>106cm^(-3))and low temperatures(T_(dust)<18 K)involved.Under such conditions,many molecules become depleted from the gas phase by freezing out onto dust grains.However,the N-bearing and deuterated species could remain gaseous under these extreme conditions,suggesting that they may serve as ideal tracers.In this paper,using the Plateau de Bure Interferometer and Very Large Array observations at 1.3 mm,3.5 mm,and 1.3 cm,we investigate the possible habitats for NH_(3),NH_(2)D,H^(13)CN,HC^(15)N,SO,and C^(18)O in eight massive precluster and protocluster clumps G18.17,G18.21,G23.97N,G23.98,G23.44,G23.97S,G25.38,and G25.71.We found that the NH3cores are in good agreement with the 3.5 mm peak emission,but the NH_(3)is much more extended than the 3.5 mm emission structure.The SO distributions agree well with the 3.5 mm peaks for the evolved star formation stage,but we did not detect any SO emission in the four earliest star formation sources.C^(18)O is a poor tracer in conditions of the cold(■18 K)and dense(■10^(4)cm^(-3))cores,e.g.,the prestellar cores.We also found that the NH_(2)D cores are mainly located in the temperature range of 13.0-20.0 K,and the NH_(2)D lines may be strongly depleted above 20 K.

关键词： galaxies:star formation techniques:interferometric methods:observational

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

在线全文

学校读者我要写书评

暂无评论

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

Application of a Space-based Optical Interferometer Toward Measuring Cosmological Distances of Quasars

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2022年第3期22卷 100-114页

作者： Ying-Ke Huang Yue-Dong Fang Kai-Xing Lu Zhi-Xiang Zhang Ji-Lin Liu Sha-sha Li Bao-Rui Luo Qin Lin Zhuo-Xi Huo Qian Xuesen Laboratory of Space Technology China Academy of Space TechnologyBeijing 100081China Yunnan Observatories Chinese Academy of SciencesKunming 650011China Department of Astronomy Xiamen UniversityXiamenFujian 361005China

Measuring quasar distance through joint analysis of spectroastrometry and reverberation mapping observations is a new method for driving the development of cosmology.In this paper,we carry out detailed simulation and analysis to study the effect of four basic observational parameters(baseline length,exposure time,equivalent diameter and spectral resolution)on the data quality of differential phase curves(DPCs),and furthermore on the accuracy of distance measurement.In our simulation,we adopt an axisymmetrical disk model of a broad line region(BLR)to generate differential phase signals.We find that the differential phases and their Poisson errors could be amplified by extending the baseline,while the influence of optical path difference errors can be reduced during fitting the BLR model.Longer exposure time or larger equivalent diameter helps reduce the absolute Poisson error.Therefore,the relative error of DPCs could be reduced by increasing any of the above three parameters,then the accuracy of distance measurement could be improved.In contrast,the uncertainty of absolute angular distances(D_(A))could be improved with higher spectral resolution,although the relative error of DPCs would be amplified.We show how the uncertainty of distance measurement varies with the relative error of DPCs.For our specific set of model parameters,without considering more complicated structures and kinematics of BLRs in our simulation,it is found that the relative error of DPCs<20%is a limit for accurate distance measurement.The relative error of DPCs has a lower limit(roughly 5%)and the uncertainty in distance measurement can be better than 2%.

关键词： (galaxies:)quasars:emission lines techniques:interferometric (cosmology:)distance scale

A Fast Radio Burst Backend for the Tianlai Dish Pathfinder Array

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2022年第12期22卷 211-223页

作者： Zijie Yu Furen Deng Shijie Sun Chenhui Niu Jixia Li Fengquan Wu Wei-Yang Wang Yougang Wang Hui Feng Lin Shu Jie Hao Reza Ansari Albert Stebbins Xuelei Chen National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China Department of Astronomy Peking UniversityBeijing 100871China Kavli Institute for Astronomy and Astrophysics Peking UniversityBeijing 100871China Institute of Automation Chinese Academy of SciencesBeijing 100190China Guangdong Institute of Artificial Intelligence and Advanced Computing Guangzhou 510535China UniversitéParis-Saclay CNRS/IN2P3IJCLabF-91405 OrsayFrance Fermi National Accelerator Laboratory P.O.Box 500BataviaIL 60510-5011United States of America Department of Physics College of SciencesNortheastern UniversityShenyang 110819China Center of High Energy Physics Peking UniversityBeijing 100871China

The Tianlai Dish Pathfinder Array is a radio interferometer array consisting of 16 six-meter dish antennas.The original digital backend integration time is at the seconds level,designed for H I intensity mapping experiment.A new digital backend with millisecond response is added to enable it to search for fast radio burst during its observations.The design and calibration of this backend,and the real time search pipeline for it are described in this paper.It is capable of forming 16 digital beams for each linear polarization,covering an area of 19.6 square degrees.The search pipeline is capable of searching for,recording and classifying FRBs automatically in real time.In commissioning,we succeeded in capturing the signal pulses from the pulsars PSR B0329+54 and B2021+51.

关键词： instrumentation:miscellaneous techniques:interferometric telescopes radio continuum:general (stars:)pulsars:general

Deconvolution with hybrid parameterizations for radio emission reconstruction

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2021年第4期21卷 287-296页

作者：张利 Long Xu Li-Gong Mi Ming Zhang Xiang Liu Feng Wang Yun-Jun Ruan Dan-Yang Li College of Big Data and Information Engineering Guizhou UniversityGuiyang 550025China Key Laboratory of Solar Activity National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China Xinjiang Astronomical Observatory Chinese Academy of SciencesUrumqi 830011China Key Laboratory of Radio Astronomy Chinese Academy of SciencesUrumqi 830011China Center for Astrophysics Guangzhou UniversityGuangzhou 510006China

Deconvolution is used to eliminate imperfections in the point spread function,such as sidelobes caused by incomplete sampling of radio telescopes,and is a key technology for radio synthesis imaging.Modern telescopes have such high sensitivities that the observed celestial images may contain both compact and diffuse emission.This essentially requires deconvolution technology to have the ability to model both.In this paper,a deconvolution algorithm based on hybrid parameterization is proposed for the rapid reconstruction of complex celestial structures.In this algorithm,scale-free parameterization is utilized to reconstruct compact emission,while multi-scale parameterization is employed to reconstruct diffuse emission.Simulated data representing Square Kilometre Array(SKA)observations with realistic celestial brightness distributions are applied to test the performance of the algorithm.Our experiments show that,compared with other state-of-the-art deconvolution algorithms,the algorithm proposed in this paper can reconstruct complex celestial structures well and provide competitive reconstruction results while greatly improving the reconstruction speed.

关键词： methods:data analysis techniques:image processing techniques:interferometric

DEFPOS and Its First Results

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Astronomy and Astrophysics 2005年第2期5卷 211-220页

作者： M.■ahan .Ye■ingil N.Aksaker .Kιzιo■lu M.Akyιlmaz Department of Physics Cukurova University 01330AdanaTurkeyDepartment of Physics Cukurova University01330AdanaTurkey Department of Physics Cukurova University01330AdanaTurkeyDepartment of Physics Middle East Technical UniversityAnkaraTurkeyDepartment of Physics Cukurova University01330AdanaTurkey

A spectrometer was built to examine the interstellar medium (ISM) using the hydrogen Balmer α line. It is called Dual Etalon Fabry-Perot Optical Spectrometer (DEFPOS). DEFPOS will be coupled to coudé exit of the 150 cm telescope (RTT150) installed at TüBITAK National Observatory (TUG). DEFPOS was ready for observations about two years ago, but work was still continuing on the RTT150 coudé exit alignment. So we have started observing HII regions with DEFPOS without the RTT150. We present here some characteristics of the instrument and some of the results obtained.

关键词： ISM: general ISM: HII regions instrumentation: Interferometers techniques:interferometric atmospheric effect

Reflections and standing waves on the Tianlai cylinder array

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2021年第3期21卷 73-85页

作者： Ji-Xia Li Feng-Quan Wu Shi-Jie Sun Zi-Jie Yu Shi-Fan Zuo Ying-Feng Liu You-Gang Wang Cong Zhang Reza Ansari Peter Timbie Xuelei Chen National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China School of Astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049China Center for Astrophysics and Department of Astronomy Tsinghua UniversityBeijing 100084China IJC Lab CNRS/IN2P3&Universite Paris-Saclay15 rue Georges Cl´emenceau91405 OrsayFrance´ Department of Physics University of Wisconsin Madison1150 University AveMadison WI 53703USA Center of High Energy Physics Peking UniversityBeijing 100871China

In 21 cm intensity mapping,the spectral smoothness of the foreground is exploited to separate it from the much weaker 21 cm signal.However,the non-smooth frequency response of the instrument complicates this process.Reflections and standing waves generate modulations on the frequency response.Here we report the analysis of the standing waves in the bandpass of the signal channels of the Tianlai Cylinder Array.By Fourier transforming the bandpass into the delay time domain,we find various standing waves generated on the telescope.A standing wave with time delay at~142 ns is most clearly identified which is produced in the 15-meter feed cable.We also identify a strong peak at a shorter delay ofτ<50 ns,which may be a mix of the standing wave between the reflector and feed,and the standing wave on the 4 m intermediate frequency(IF)cable.We also show that a smoother frequency response could be partially recovered by removing the reflection-inducted modulations.However,the standing wave on the antenna is direction-dependent,which poses a more difficult challenge for high precision calibration.

关键词： techniques:interferometric methods:data analysis

Distortion mapping correction in the AIMS primary mirror testing by a computer-generated hologram

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2021年第7期21卷 99-106页

作者： Ke-Wei E Jian-Ke Zhao Bo Wang Dong-Guang Wang Yu-Liang Shen Xin Fu Song-Bo Xu Jing Li Xun Xue Ming Chang Yan Zhou Xi’an Institute of Optics and Precision Mechanics Chinese Academy of SciencesXi’an 710119China Nanjing Astronomical Instruments Chinese Academy of SciencesNanjing 210042China National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China

The National Solar Observatory is currently developing the Accurate Infrared Magnetic Field Measurements of the Sun(AIMS). The primary mirror of the AIMS solar telescope is an off-axis parabolic with a diameter of 1 m and with a large off-axis amount of 1 m. Due to the surface figure of the primary mirror under the used state is directly related to image quality of the whole system, a computer-generated hologram(CGH) is carried out to test the primary mirror, and the test results are used to polish the mirror to a higher surface accuracy. However, the fact that the distortion exists in the testing results leads to the failure of a further guide to deterministic optical processing. In this paper, a distortion correction method is proposed, which uses an orthogonal set of vector polynomials to mapping the coordinates of the mirror and the pixels of fringes, and then an interpolation method is adopted to obtain the corrected results. The testing accuracy by using CGH is also verified by an auto-collimate test experiment. According to the distorted corrected results, the root-mean-square of the surface figure is about 1/50λ(λ=632.8 nm) after polishing.

关键词： telescopes techniques:interferometric methods:astronomical instrumentation methods and techniques

Observational characteristics of SiO masers around VX Sgr

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2020年第12期20卷 196-204页

作者： Jiang-Bo Su Zhi-Qiang Shen Xi Chen Jing Liu Yan Wang Yi-Bin Zhao Department of Physics and Electronics Yuncheng UniversityYuncheng 044000China Shanghai Astronomical Observatory Chinese Academy of SciencesShanghai 200030China Center for Astrophysics Guangzhou UniversityGuangzhou 510006China

SiO maser VLBA observations toward VX Sgr are performed at five epochs, and lots of maser spots are obtained. We make a statistical analysis on these spots. It is shown that the apparent sizes and the fluxes of maser spots decrease with increasing the distance from the central star. In addition, the similarity between the v = 1,2(J =1–0) spectrums increases with epochs, consistent with the full width at half maximum(FWHM), while the total fluxes increase. The results may be related to the changeable pumping mechanisms.

关键词： masers stars:individual(VX Sgr) techniques:interferometric turbulence