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The First Ground-based White Light Lunar Polarization Imaging:A New Kind of FeO Observation on the Near Side of the Moon
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作者 Wei-Nan Wang Jin-Song Ping +4 位作者 Ming-Yuan Wang Wen-Zhao Zhang Han-Lin Ye Xing-Wei Han Song-Feng Kou 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第6期1-6,共6页
Lunar optical polarization is a fascinating phenomenon that occurs when sunlight reflects off the surface of the Moon and becomes polarized.This study employs a novel split-focus plane polarimetric camera to conduct t... Lunar optical polarization is a fascinating phenomenon that occurs when sunlight reflects off the surface of the Moon and becomes polarized.This study employs a novel split-focus plane polarimetric camera to conduct the initial white light polarimetric observations on the near side of the Moon.We obtained the linear degree of polarization(DOP)parameters of white light by observation from the eastern and western hemispheres of the Moon.The findings indicate that the white light polarization is lower in the lunar highland than in the lunar maria overall.Combining the analysis of lunar soil samples,we noticed and determined that the DOP parameters of white light demonstrate high consistency with iron oxide on the Moon.This study may serve as a new diagnostic tool for the Moon. 展开更多
关键词 techniques:photometric POLARIZATION methods:observational MOON
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The In-Flight Realtime Trigger and Localization Software of GECAM
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作者 Xiao-Yun Zhao Shao-Lin Xiong +86 位作者 Xiang-Yang Wen Xin-Qiao Li Ce Cai Shuo Xiao Qi Luo Wen-Xi Peng Dong-Ya Guo Zheng-Hua An Ke Gong Jin-Yuan Liao Yan-Qiu Zhang Yue Huang Lu Li Xing Wen Fei Zhang Jing Duan Chen-Wei Wang Dong-Li Shi Peng Zhang Qi-Bin Yi Chao-Yang Li Yan-Bing Xu Xiao-Hua Liang Ya-Qing Liu Da-Li Zhang Xi-Lei Sun Fan Zhang Gang Chen Huan-Yu Wang Sheng Yang Xiao-Jing Liu Min Gao Mao-Shun Li Jin-Zhou Wang Xing Zhou Yi Zhao Wang-Chen Xue Chao Zheng Jia-Cong Liu Xing-Bo Han Jin-Ling Qi Jia Huang Ke-Ke Zhang Can Chen Xiong-Tao Yang Dong-Jie Hou Yu-Sa Wang Rui Qiao Xiang Ma Xiao-Bo Li Ping Wang Xin-Ying Song Li-Ming Song Shi-Jie Zheng Bing Li Hong-Mei Zhang Yue Zhu Wei Chen Jian-Jian He Zhen Zhang Jin Hou Hong-Jun Wang Yan-Chao Hao Xiang-Yu Wang Zong-Yuan Yang Zhi-Long Wen Zhi Chang Yuan-Yuan Du Rui Gao Xiao-Fei Lan Yan-Guo Li Gang Li Xu-Fang Li Fang-Jun Lu Hong Lu Bin Meng Feng Shi Hui Wang Hui-Zhen Wang Yu-Peng Xu Jia-Wei Yang Xue-Juan Yang Shuang-Nan Zhang Chao-Yue Zhang Cheng-Mo Zhang Zhi-Cheng Tang Cheng Cheng 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第10期11-24,共14页
Realtime trigger and localization of bursts are the key functions of GECAM,an all-sky gamma-ray monitor launched on 2020 December 10.We developed a multifunctional trigger and localization software operating in the CP... Realtime trigger and localization of bursts are the key functions of GECAM,an all-sky gamma-ray monitor launched on 2020 December 10.We developed a multifunctional trigger and localization software operating in the CPU of the GECAM Electronic Box.This onboard software has the following features:high trigger efficiency for real celestial bursts with a suppression of false triggers caused by charged particle bursts and background fluctuation,dedicated localization algorithm optimized for both short and long bursts,and low time latency of the trigger information which is downlinked through the Global Short Message Communication service of the global BeiDou navigation system.This paper provides a detailed description of the design and development of the trigger and localization software system for GECAM.It covers the general design,workflow,the main functions,and the algorithms used in the system.The paper also includes on-ground trigger tests using simulated gamma-ray bursts generated by a dedicated X-ray tube,as well as an overview of the performance for real celestial bursts during its in-orbit operation. 展开更多
关键词 telescopes instrumentation:detectors methods:observational
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A Novel Two-dimensional Low-redundancy Array Design for Solar Radio Imaging
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作者 Weidan Zhang Bing Wang +3 位作者 Zhao Wu Guang Lu Yao Chen Yan Fabao 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第9期178-189,共12页
The radioheliograph is an extensive array of antennas operating on the principle of aperture synthesis to produce images of the Sun.The image acquired by the telescope results from convoluting the Sun’s true brightne... The radioheliograph is an extensive array of antennas operating on the principle of aperture synthesis to produce images of the Sun.The image acquired by the telescope results from convoluting the Sun’s true brightness distribution with the antenna array’s directional pattern.The imaging quality of the radioheliograph is affected by a multitude of factors,with the performance of the“dirty beam”being simply one component.Other factors such as imaging methods,calibration techniques,clean algorithms,and more also play a significant influence on the resulting image quality.As the layout of the antenna array directly affects the performance of the dirty beam,the design of an appropriate antenna configuration is critical to improving the imaging quality of the radioheliograph.Based on the actual needs of observing the Sun,this work optimized the antenna array design and proposed a twodimensional low-redundancy array.The proposed array was compared with common T-shaped arrays,Y-shaped arrays,uniformly spaced circular arrays,and three-arm spiral arrays.Through simulations and experiments,their performance in terms of sampling point numbers,UV coverage area,beam-half width,sidelobe level,and performance in the absence of antennas are compared and analyzed.It was found that each of these arrays has its advantages,but the two-dimensional low-redundancy array proposed in this paper performs best in overall evaluation.It has the shortest imaging calculation time among the array types and is highly robust when antennas are missing,making it the most suitable choice. 展开更多
关键词 INTERFEROMETERS methods:observational techniques:interferometric
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The Influence of the Sun and Moon on the Observation of Very High Energy Gamma-ray Sources Using EAS Arrays
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作者 Tao Wen Songzhan Chen Benzhong Dai 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第6期245-252,共8页
With great advance of ground-based extensive air shower arrays,such as LHAASO and HAWC,many very high energy(VHE)gamma-ray sources have been discovered and are being monitored regardless of the day and the night.Hence... With great advance of ground-based extensive air shower arrays,such as LHAASO and HAWC,many very high energy(VHE)gamma-ray sources have been discovered and are being monitored regardless of the day and the night.Hence,the Sun and Moon would have some impacts on the observation of gamma-ray sources,which have not been taken into account in previous analysis.In this paper,the influence of the Sun and Moon on the observation of very high energy gamma-ray sources when they are near the line of sight of the Sun or Moon is estimated.The tracks of all the known VHE sources are scanned and several VHE sources are found to be very close to the line of sight of the Sun or Moon during some period.The absorption of very high energy gamma rays by sunlight is estimated with detailed method and some useful conclusions are achieved.The main influence is the block of the Sun and Moon on gamma rays and the shadow on the cosmic ray background.The influence is investigated considering the detector angular resolution and some strategies on data analysis are proposed to avoid the underestimation of the gamma-ray emission. 展开更多
关键词 astroparticle physics Sun:general methods:observational Sun:UV radiation
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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
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作者 Quan-Ling Cui Chuan-Peng Zhang Jun-Jie Wang 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第4期237-252,共16页
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 be... 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. 展开更多
关键词 galaxies:star formation techniques:interferometric methods:observational
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The Bright Single Pulse Emission from PSR B1133+16
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作者 Jun Tan Zhi-Gang Wen +12 位作者 Zhen Wang Xue-Feng Duan Hong-Guang Wang Na Wang Vishal Gajjar Jian-Ping Yuan Rai Yuen Wen-Ming Yan Jian-Ling Chen Wei Han Hui Wang Cheng-Bing Lyu Ai-Jun Dong 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第4期253-261,共9页
We have conducted a comprehensive investigation into the bright single pulse emission from PSR B1133+16using the Giant Metrewave Radio Telescope.High time resolution data(61μs)were obtained at a center frequency of 3... We have conducted a comprehensive investigation into the bright single pulse emission from PSR B1133+16using the Giant Metrewave Radio Telescope.High time resolution data(61μs)were obtained at a center frequency of 322 MHz with a bandwidth of 32 MHz over a continuous observation period of 7.45 hr.A total of 1082 bright pulses were sporadically detected with peak flux densities ranging from 10 to 23 times stronger than the average pulse profile.However,no giant pulse-like emission with a relative pulse energy larger than 10 and extremely short duration was detected,indicating that these bright pulses cannot be categorized as giant pulse emission.The majority of these bright pulses are concentrated in pulse phases at both the leading and trailing windows of the average pulse profile,with an occurrence ratio of approximately 2.74.The pulse energy distribution for all individual pulses can be described by a combination of two Gaussian components and a cutoff power-law with an index of α=-3.2.An updated nulling fraction of 15.35%±0.45% was determined from the energy distribution.The emission of individual pulses follows a log-normal distribution in peak flux density ratio.It is imperative that regular phase drifting in bright pulse sequence is identified in both the leading and trailing components for the first time.Possible physical mechanisms are discussed in detail to provide insights into these observations. 展开更多
关键词 (stars:)pulsars:general (stars:)pulsars:individual(PSR B1133+16) methods:observational methods:data analysis
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BSN:Photometric Light Curve Analysis of Two Contact Binary Systems LS Del and V997 Cyg
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作者 Atila Poro Mehmet Tanriver +9 位作者 Elham Sarvari Shayan Zavvarei Hossein Azarara Laurent Corp Sabrina Baudart Asma Ababafi Nazanin Kahali Poor Fariba Zare Ahmet Bulut Ahmet Keskin 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第4期192-213,共22页
The light curve analyses and orbital period variations for two contact binary stars,LS Del and V997 Cyg,are presented in this work which was conducted in the frame of the Binary Systems of South and North project Grou... The light curve analyses and orbital period variations for two contact binary stars,LS Del and V997 Cyg,are presented in this work which was conducted in the frame of the Binary Systems of South and North project Ground-based photometric observations were performed at two observatories in France.We used the Transiting Exoplanet Survey Satellite(TESS)data for extracting times of minima and light curve analysis of the targe systems.The O-C diagram for both systems displays a parabolic trend.LS Del and V997 Cyg’s orbital periods are increasing at rates of dP/dt=7.20×10^(-08)days yr^(-1)and dP/dt=2.54×10^(-08)days yr^(-1),respectively Therefore,it can be concluded that mass is being transferred from the less massive star to the more massive component with a rate of dM/dt=-1.96×10^(-7)M_(⊙)yr^(-1)for the LS Del system,and dM/dt=-3.83×10^(-7)M_(⊙)yr-1for V997 Cyg.The parameters of a third possible object in the system are also considered.The PHysics Of Eclipsing BinariEs Python code was used to analyze the light curves.The light curve solutions needed a cold starspot due to the asymmetry in the LS Del system’s light curve maxima.The mass ratio fill-out factor,and star temperature all indicate that both systems are contact binary types in this investigation.Two methods were applied to estimate the absolute parameters of the systems:one method relied on the parallax of Gaia DR3,and the other used a P-M relationship.The positions of the systems are also depicted on the M-L,M-R q-L_(ratio),and logM_(tot)-logJ_(0)diagrams.We recommend that further observations and investigations be done on the existence of a fourth body in this system. 展开更多
关键词 (stars:)binaries:eclipsing methods:observational stars:individual(LS Del and V997 Cyg)
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Study of elastic wave propagation in two phase anisotropic media by numerical modeling of pseudospectral method 被引量:5
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作者 刘洋 李承楚 《Acta Seismologica Sinica(English Edition)》 CSCD 2000年第2期143-150,共8页
When there exists anisotropy in underground media elastic parameters of the observed coordinate possibly do not coincide with that of the natural coordinate. According to the theory that the density of potential energ... When there exists anisotropy in underground media elastic parameters of the observed coordinate possibly do not coincide with that of the natural coordinate. According to the theory that the density of potential energy, dissipating energy is independent of the coordinate, the relationship of elastic parameters between two coordinates is derived for two-phase anisotropic media. Then, pseudospectral method to solve wave equations of two-phase anisotropic media is derived. At last, we use this method to simulate wave propagation in two-phase anisotropic media four types of waves are observed in the snapshots, i.e., fast P wave and slow P wave, fast S wave and slow S wave. Shear wave splitting, SV wave cusps and elastic wave reflection and transmission are also observed. 展开更多
关键词 two-phase anisotropy natural coordinate observed coordinate elastic parameters nu merical modeling pseudospectral method
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Generating a radioheliograph image from SDO/AIA data with the machine learning method
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作者 Pei-Jin Zhang Chuan-Bing Wang Guan-Shan Pu 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2020年第12期317-322,共6页
Radioheliograph images are essential for the study of solar short term activities and long term variations, while the continuity and granularity of radioheliograph data are not so ideal, due to the short visible time ... Radioheliograph images are essential for the study of solar short term activities and long term variations, while the continuity and granularity of radioheliograph data are not so ideal, due to the short visible time of the Sun and the complex electron-magnetic environment near the ground-based radio telescope. In this work, we develop a multi-channel input single-channel output neural network, which can generate radioheliograph image in microwave band from the Extreme Ultra-violet(EUV) observation of the Atmospheric Imaging Assembly(AIA) on board the Solar Dynamic Observatory(SDO). The neural network is trained with nearly 8 years of data of Nobeyama Radioheliograph(No RH) at 17 GHz and SDO/AIA from January 2011 to September 2018. The generated radioheliograph image is in good consistency with the well-calibrated No RH observation. SDO/AIA provides solar atmosphere images in multiple EUV wavelengths every 12 seconds from space, so the present model can fill the vacancy of limited observation time of microwave radioheliograph, and support further study of the relationship between the microwave and EUV emission. 展开更多
关键词 Sun:radio radiation methods:observational methods:data analysis
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An improved solution to geometric distortion using an orthogonal method
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作者 Huan-Wen Peng Qing-Yu Peng Na Wang 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2017年第2期89-96,共8页
The geometric distortion of a CCD field of view has a direct influence on the positional measurements of CCD observations. In order to obtain high precision astrometric results, the geometric distortion should be deri... The geometric distortion of a CCD field of view has a direct influence on the positional measurements of CCD observations. In order to obtain high precision astrometric results, the geometric distortion should be derived and corrected precisely. As presented in our previous work, a convenient solution has been carried out and has also been applied to observations of Phoebe. In order to fur- ther improve the solution, an orthogonal method based on Zernike polynomials is used in this work. Four nights of CCD observations including Himalia, the sixth satellite of Jupiter, and open clusters (NGC 1664 or NGC 2324) on each night have been processed as an application. The observations were obtained from the 2.4 m telescope administered by Yunnan Observatories. The catalog UCAC4 was used to match reference stars in all of the CCD frames. The ephemeris of Himalia is retrieved from the Institut de M6canique C61este et de Calcul des Ephemerides (IMCCE). Our results show that the means of observed minus calculated (O - C) positional residuals are -0.034 and -0.026 arcsec in right ascension and declination, respectively. The corresponding standard deviations are 0.031" and 0.028". The measurement dispersion is significantly improved compared to that by using our previous solution. 展开更多
关键词 astrometry -- planets and satellites: individual (Himalia) -- methods: observational
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Clinical observation of Hot Compress and Mounting Medicine Method
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作者 Zhang Lide(Physiotherapy Dept.of Yangzhou Mineral Bureau General Hospital,Shandong Province) 《中国针灸》 CAS CSCD 北大核心 1995年第S2期336-336,共1页
ClinicalobservationofHotCompressandMountingMedicineMethod¥ZhangLide(PhysiotherapyDept.ofYangzhouMineralBurea... ClinicalobservationofHotCompressandMountingMedicineMethod¥ZhangLide(PhysiotherapyDept.ofYangzhouMineralBureauGeneralHospital,... 展开更多
关键词 Clinical observation of Hot Compress and Mounting Medicine method
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How to co-add images? I. A new iterative method for image reconstruction of dithered observations
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作者 Lei Wang Guo-Liang Li 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2017年第10期1-14,共14页
By employing the previous Voronoi approach and replacing its nearest neighbor approx- imation with Drizzle in iterative signal extraction, we develop a fast iterative Drizzle algorithm, namedfiDrizzle, to reconstruct ... By employing the previous Voronoi approach and replacing its nearest neighbor approx- imation with Drizzle in iterative signal extraction, we develop a fast iterative Drizzle algorithm, namedfiDrizzle, to reconstruct the underlying band-limited image from undersampled dithered frames. Compared with the existing iDrizzle, the new algorithm improves rate of convergence and accelerates the computational speed. Moreover, under the same conditions (e.g. the same number of dithers and iterations), fiDrizzle can make a better quality reconstruction than iDrizzle, due to the newly discov- ered High Sampling caused Decelerating Convergence (HSDC) effect in the iterative signal extraction process.fiDrizzle demonstrates its powerful ability to perform image deconvolution from undersampled dithers. 展开更多
关键词 techniques: image processing -- methods: observational -- stars: imaging -- planets andsatellites: detection -- gravitational lensing
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Light curve inversion of asteroid(585)Bilkis with Lommel-Seeliger ellipsoid method
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作者 Ao Wang Xiao-Bin Wang +2 位作者 Karri Muinonen Xianming L.Han Yi-Bo Wang 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2016年第12期19-26,共8页
The basic physical parameters of asteroids, such as spin parameters, shape and scattering parameters, can provide us with information on the formation and evolution of both the asteroids themselves and the entire sola... The basic physical parameters of asteroids, such as spin parameters, shape and scattering parameters, can provide us with information on the formation and evolution of both the asteroids themselves and the entire solar system. In a majority of asteroids, the disk-integrated photometry measurement constitutes the primary source of the above knowledge. In the present paper, newly observed photometric data and existing data on(585) Bilkis are analyzed based on a Lommel-Seeliger ellipsoid model. With a Markov chain Monte Carlo(MCMC) method, we have determined the spin parameters(period, pole orientation)and shape(b/a, c/a) of(585) Bilkis and their uncertainties. As a result, we obtained a rotational period of 8.5738209 h with an uncertainty of 9×10^-7h, and derived a pole of(136.46°, 29.0°) in the ecliptic frame of J2000.0 with uncertainties of 0.67°and 1.1°in longitude and latitude respectively. We also derived triaxial ratios b/a and c/a of(585) Bilkis as 0.736 and 0.70 with uncertainties of 0.003 and 0.03 respectively. 展开更多
关键词 asteroids -- photometric observation -- spin parameter -- shape -- MCMC method
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Searching for the Nano-Hertz Stochastic Gravitational Wave Background with the Chinese Pulsar Timing Array Data ReleaseⅠ 被引量:18
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作者 Heng Xu Siyuan Chen +24 位作者 Yanjun Guo Jinchen Jiang Bojun Wang Jiangwei Xu Zihan Xue RNicolas Caballero Jianping Yuan Yonghua Xu Jingbo Wang Longfei Hao Jingtao Luo Kejia Lee Jinlin Han Peng Jiang Zhiqiang Shen Min Wang Na Wang Renxin Xu Xiangping Wu Richard Manchester Lei Qian Xin Guan Menglin Huang Chun Sun Yan Zhu 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2023年第7期300-311,共12页
Observing and timing a group of millisecond pulsars with high rotational stability enables the direct detection of gravitational waves(GWs).The GW signals can be identified from the spatial correlations encoded in the... Observing and timing a group of millisecond pulsars with high rotational stability enables the direct detection of gravitational waves(GWs).The GW signals can be identified from the spatial correlations encoded in the times-of-arrival of widely spaced pulsar-pairs.The Chinese Pulsar Timing Array(CPTA)is a collaboration aiming at the direct GW detection with observations carried out using Chinese radio telescopes.This short article serves as a“table of contents”for a forthcoming series of papers related to the CPTA Data Release 1(CPTA DR1)which uses observations from the Five-hundred-meter Aperture Spherical radio Telescope.Here,after summarizing the time span and accuracy of CPTA DR1,we report the key results of our statistical inference finding a correlated signal with amplitude logA_(c)=-14.4_(-2.8)^(+1.0)for spectral index in the range ofα∈[-1.8,1.5]assuming a GW background(GWB)induced quadrupolar correlation.The search for the Hellings–Downs(HD)correlation curve is also presented,where some evidence for the HD correlation has been found that a 4.6σstatistical significance is achieved using the discrete frequency method around the frequency of 14 n Hz.We expect that the future International Pulsar Timing Array data analysis and the next CPTA data release will be more sensitive to the n Hz GWB,which could verify the current results. 展开更多
关键词 (stars:)pulsars:general gravitational waves methods:statistical methods:observational
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Detecting HI Galaxies with Deep Neural Networks in the Presence of Radio Frequency Interference 被引量:1
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作者 Ruxi Liang Furen Deng +9 位作者 Zepei Yang Chunming Li Feiyu Zhao Botao Yang Shuanghao Shu Wenxiu Yang Shifan Zuo Yichao Li Yougang Wang Xuelei Chen 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2023年第11期38-50,共13页
In the neutral hydrogen(H I)galaxy survey,a significant challenge is to identify and extract the H I galaxy signal from the observational data contaminated by radio frequency interference(RFI).For a drift-scan survey,... In the neutral hydrogen(H I)galaxy survey,a significant challenge is to identify and extract the H I galaxy signal from the observational data contaminated by radio frequency interference(RFI).For a drift-scan survey,or more generally a survey of a spatially continuous region,in the time-ordered spectral data,the H I galaxies and RFI all appear as regions that extend an area in the time-frequency waterfall plot,so the extraction of the H I galaxies and RFI from such data can be regarded as an image segmentation problem,and machine-learning methods can be applied to solve such problems.In this study,we develop a method to effectively detect and extract signals of H I galaxies based on a Mask R-CNN network combined with the PointRend method.By simulating FAST-observed galaxy signals and potential RFI impact,we created a realistic data set for the training and testing of our neural network.We compared five different architectures and selected the best-performing one.This architecture successfully performs instance segmentation of H I galaxy signals in the RFI-contaminated time-ordered data,achieving a precision of 98.64%and a recall of 93.59%. 展开更多
关键词 methods:data analysis methods:observational techniques:image processing
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An Independent Degree-eight Mars Gravity Field Model and the Expected Results from the Tianwen-1 Mission 被引量:2
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作者 Shanhong Liu Jianfeng Cao +3 位作者 Jianguo Yan Hao Huang Xie Li Jean-Pierre Barriot 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2023年第10期267-276,共10页
Tianwen-1 is China's first independent interplanetary exploration mission,targeting Mars,and includes orbiting,landing,and rover phases.Similar to previous Mars missions,the Tianwen-1 orbiter was designed for pola... Tianwen-1 is China's first independent interplanetary exploration mission,targeting Mars,and includes orbiting,landing,and rover phases.Similar to previous Mars missions,the Tianwen-1 orbiter was designed for polar orbits during the scientific mission period but has an exceptional eccentricity of approximately 0.59.We provide the first independent eight-degree Martian gravity field model in this paper,which was developed exclusively by a team working in China with our independent software as well,based on about two months of radiometric Doppler and range data from only the Tianwen-1 mission.This model is independent from the models created by the groups at NASA Jet Propulsion Laboratory and Goddard Space Flight Center in the United States,as well as the Centre National d'Etudes Spatiales in France.Furthermore,in order to optimize the engineering and scientific benefits,we proposed a number of potential orbits for the extended Tianwen-1 mission.In order to solve a higher-degree independent Mars gravity field model,the viability of modifying the perigee height was investigated,with the priority considerations of fuel savings and implementation hazards being controlled. 展开更多
关键词 GRAVITATION planets and satellites:fundamental parameters methods:observational
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Portable adaptive optics for exoplanet imaging 被引量:6
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作者 Yong-Tian Zhu Jiang-Pei Dou +3 位作者 Xi Zhang Gang Zhao Jing Guo Leopoldo Infante 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2021年第4期110-118,共9页
The portable adaptive optics(PAO)device is a low-cost and compact system,designed for 4-meter class telescopes that have no adaptive optics(AO)system,because of the physical space limitation at the Nasmyth or Cassegra... The portable adaptive optics(PAO)device is a low-cost and compact system,designed for 4-meter class telescopes that have no adaptive optics(AO)system,because of the physical space limitation at the Nasmyth or Cassegrain focus and the historically high cost of conventional AO.The initial scientific observations of the PAO are focused on the direct imaging of exoplanets and sub-stellar companions.This paper discusses the concept of PAO and the associated high-contrast imaging performance in our recent observational runs.PAO deliver a Strehl ratio better than 60%in H band under median seeing conditions of 1".Combined with our dedicated image rotation and subtraction(IRS)technique and the optimized IRS(O-IRS)algorithm,the averaged contrast ratio for a 5≤V_(mag)≤9 primary star is 1.3×10^(-5)and3.3×10^(-6)at angular distance of 0.36"with exposure time of 7 minutes and 2 hours,respectively.PAO has successfully revealed the known exoplanet ofκAnd b in our recent observation with the 3.5-meter ARC telescope at Apache Point Observatory.We have performed the associated astrometry and photometry analysis of the recoveredκAnd b planet,which gives a projected separation of 0.98"±0.05",a position angle of 51.1°±0.5°and a mass of 10.15_(-1.255)^(+2.19) MJup.These results demonstrate that PAO can be used for direct imaging of exoplanets with medium-sized telescopes. 展开更多
关键词 stars:imaging instrumentation:adaptive optics instrumentation:high angular resolution methods:observational techniques:image processing
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Astronomy from Dome A in Antarctica 被引量:4
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作者 Zhaohui Shang 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2020年第10期353-384,共32页
Dome A in Antarctica has been demonstrated to be the best site on earth for optical,infrared,and terahertz astronomical observations by more and more evidence,such as excellent free-atmosphere seeing,extremely low per... Dome A in Antarctica has been demonstrated to be the best site on earth for optical,infrared,and terahertz astronomical observations by more and more evidence,such as excellent free-atmosphere seeing,extremely low perceptible water vapor,low sky background,and continuous dark time,etc.In this paper,we present a complete picture of the development of astronomy at Dome A from the very beginning,review recent progress in time-domain astronomy,demonstrate exciting results of the site testing,and address the challenges in instrumentation.Currently proposed projects are briefly discussed. 展开更多
关键词 instrumentation:miscellaneous methods:observational techniques:miscellaneous telescopes atmospheric effects site testing stars:variables:general
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Measurements of atmospheric turbulence parameters at Vainu Bappu Observatory using short-exposure CCD images 被引量:2
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作者 Sreekanth Reddy V. Ravinder Kumar Banyal +1 位作者 Sridharan R. Aishwarya Selvaraj 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2019年第5期123-132,共10页
We report atmospheric turbulence parameters, namely atmospheric seeing, tilt-anisoplanatic angle(θ_0) and coherence time(Τ_0), measured under various sky conditions, at Vainu Bappu Observatory in Kavalur. Bursts of ... We report atmospheric turbulence parameters, namely atmospheric seeing, tilt-anisoplanatic angle(θ_0) and coherence time(Τ_0), measured under various sky conditions, at Vainu Bappu Observatory in Kavalur. Bursts of short exposure images of selected stars were recorded with a high-speed, frame-transfer CCD mounted on the Cassegrain focus of a newly commissioned 1.3 m telescope. The estimated median seeing is ≈ 1.85 " at wavelength of ~ 600 nm, the image motion correlation between different pairs of stars is ~44% for θ0≈ 36" and mean Τ_0 is ≈ 2.4 ms. This work was motivated by the design considerations and expected performance of an adaptive optics system that is currently being planned for the telescope. 展开更多
关键词 ATMOSPHERIC effects TURBULENCE instrumentation:adaptive optics catalogs methods:observational
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Test area of the SAGE survey 被引量:2
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作者 Jie Zheng Gang Zhao +4 位作者 Wei Wang Zhou Fan Ke-Feng Tan Chun Li Fang Zuo 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2019年第1期29-34,共6页
Sky surveys represent one of the most important efforts to improve developments in astrophysics,especially when using new photometric bands. We are performing the Stellar Abundance and Galactic Evolution(SAGE) survey ... Sky surveys represent one of the most important efforts to improve developments in astrophysics,especially when using new photometric bands. We are performing the Stellar Abundance and Galactic Evolution(SAGE) survey with a self-designed SAGE photometric system, which is composed of eight photometric bands. The project mainly aims to study the stellar atmospheric parameters of ~0.5 billion stars in ~12 000 deg2 of the northern sky, which mainly focuses on Galactic astronomy, as well as some aspects of extragalactic astronomy. This work introduces the detailed data reduction process of the test field NGC 6791, including the data reduction of single-exposure images and stacked multi-exposure images, and properties of the final catalog. 展开更多
关键词 methods:observational techniques:photometric surveys ASTROMETRY catalogs
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