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The FRB-searching Pipeline of the Tianlai Cylinder Pathfinder Array

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Research in Astronomy and Astrophysics 2024年第8期24卷 115-134页

作者： Zijie Yu Furen Deng Shijie Sun Chenhui Niu Jixia Li Fengquan Wu Wei-Yang Wang Yougang Wang Shifan Zuo Lin Shu Jie Hao Xiaohui Liu Reza Ansari Ue-Li Pen Albert Stebbins Peter Timbie Xuelei Chen National Astronomical Observatories Chinese Academy of Sciences University of Chinese Academy of Sciences Key Laboratory of Radio Astronomy and Technology Chinese Academy of Science Institute of Astrophysics Central China Normal University Institute of Automation Chinese Academy of Sciences Guangdong Institute of Artificial Intelligence and Advanced Computing UniversitéParis—Saclay CNRS/IN2P3IJCLab Institute of Astronomy and Astrophysics Academia Sinica Canadian Institute for Theoretical Astrophysics University of Toronto60 Saint George Street Department of Physics University of Wisconsin—Madison Fermi National Accelerator Laboratory Department of Physics College of SciencesNortheastern University Center of High Energy Physics Peking University

This paper presents the design,calibration,and survey strategy of the Fast Radio Burst (FRB) digital backend and its real-time data processing pipeline employed in the Tianlai Cylinder Pathfinder *** array,consisting of three parallel cylindrical reflectors and equipped with 96 dual-polarization feeds,is a radio interferometer array designed for conducting drift scans of the northern celestial *** FRB digital backend enables the formation of 96 digital beams,effectively covering an area of approximately 40 square degrees with the 3 dB *** pipeline demonstrates the capability to conduct an automatic search of FRBs,detecting at quasi-realtime and classifying FRB candidates *** current FRB searching pipeline has an overall recall rate of88%.During the commissioning phase,we successfully detected signals emitted by four well-known pulsars:PSR B0329+54,B2021+51,B0823+26,and B2020+*** report the first discovery of an FRB by our array,designated as FRB *** also investigate the optimal arrangement for the digitally formed beams to achieve maximum detection rate by numerical simulation.

关键词： (stars:) pulsars: general instrumentation: interferometers methods: data analysis telescopes

CSST Dense Star Field Preparation: A Framework for Astrometry and Photometry for Dense Star Field Images Obtained by the China Space Station Telescope(CSST)

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Research in Astronomy and Astrophysics 2024年第7期24卷 161-172页

作者： Yining Wang Rui Sun Tianyuan Deng Chenghui Zhao Peixuan Zhao Jiayi Yang Peng Jia Huigen Liu Jilin Zhou College of Electronic Information and Optical Engineering Taiyuan University of Technology School of Astronomy&Space Science Nanjing University Peng Cheng Lab

The China Space Station Telescope(CSST) is a telescope with 2 m diameter, obtaining images with high quality through wide-field observations. In its first observation cycle, to capture time-domain observation data, the CSST is proposed to observe the Galactic halo across different epochs. These data have significant potential for the study of properties of stars and exoplanets. However, the density of stars in the Galactic center is high, and it is a well-known challenge to perform astrometry and photometry in such a dense star field. This paper presents a deep learning-based framework designed to process dense star field images obtained by the CSST, which includes photometry, astrometry, and classifications of targets according to their light curve periods. With simulated CSST observation data, we demonstrate that this deep learning framework achieves photometry accuracy of 2% and astrometry accuracy of 0.03 pixel for stars with moderate brightness mag = 24(i band), surpassing results obtained by traditional methods. Additionally, the deep learning based light curve classification algorithm could pick up celestial targets whose magnitude variations are 1.7 times larger than magnitude variations brought by Poisson photon noise. We anticipate that our framework could be effectively used to process dense star field images obtained by the CSST.

关键词： astrometry methods: data analysis techniques: photometric

Design and Application of an S-band Fast Radio Bursts Search Pipeline for the Nanshan 26 m Radio Telescope

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Research in Astronomy and Astrophysics 2024年第7期24卷 114-120页

作者： Yan-Ling Liu Mao-Zheng Chen Jian Li Jian-Ping Yuan Rai Yuen Zhi-Yong Liu Hao Yan Wen-Long Du Nan-Nan Zhai Xinjiang Astronomical Observatory Chinese Academy of Sciences Xinjiang Key Laboratory of Microwave Technology University of Chinese Academy of Sciences

Fast radio bursts(FRBs) are among the most studied radio transients in astrophysics, but their origin and radiation mechanism are still unknown. It is a challenge to search for FRB events in a huge amount of observational data with high speed and high accuracy. With the rapid advancement of the FRB research process, FRB searching has changed from archive data mining to either long-term monitoring of the repeating FRBs or all-sky surveys with specialized equipments. Therefore, establishing a highly efficient and high quality FRB search pipeline is the primary task in FRB research. Deep learning techniques provide new ideas for FRB search processing. We have detected radio bursts from FRB 20201124A in the L-band observational data of the Nanshan 26 m radio telescope(NSRT-26m) using the constructed deep learning based search pipeline named dispersed dynamic spectra search(DDSS). Afterwards, we further retrained the deep learning model and applied the DDSS framework to S-band observations. In this paper, we present the FRB observation system and search pipeline using the S-band *** carried out search experiments, and successfully detected the radio bursts from the magnetar SGR J1935+2145and FRB 20220912A. The experimental results show that the search pipeline can complete the search efficiently and output the search results with high accuracy.

关键词： methods: data analysis methods: observational radio continuum: general

On the Relation Between Symmetry of Radio Galaxies and Their Physical Parameters

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Research in Astronomy and Astrophysics 2024年第9期24卷 39-61页

作者： Mohsen Javaherian Halime Miraghaei Hooman Moradpour Research Institute for Astronomy and Astrophysics of Maragha (RIAAM) University of Maragheh

Gravity as a fundamental force plays a dominant role in the formation and evolution of cosmic objects and leaves its effect in the emergence of symmetric and asymmetric structures. Thus, analyzing the symmetry criteria allows us to uncover mechanisms behind the gravity interaction and understand the underlying physical processes that contribute to the formation of large-scale structures such as galaxies. We use a segmentation process using intensity thresholding and the k-means clustering algorithm to analyze radio galaxy images. We employ a symmetry criterion and explore the relation between morphological symmetry in radio maps and host galaxy properties. Optical properties(stellar mass, black hole mass, optical size(R50), concentration, stellar mass surface density(μ50), and stellar age) and radio properties（radio flux density, radio luminosity, and radio size） are considered. We found that there is a correlation between symmetry and radio size, indicating larger radio sources have smaller symmetry indices. Therefore, size of radio sources should be considered in any investigation of symmetry. Weak correlations are also observed with other properties, such as R50for FRI galaxies and stellar *** compare the symmetry differences between FRI and FRII radio galaxies. FRII galaxies show higher symmetry in 1.4 GHz and 150 MHz maps. Investigating the influence of radio source sizes, we discovered that this result is independent of the sizes of radio sources. These findings contribute to our understanding of the morphological properties and analyses of radio galaxies.

关键词： catalogs galaxies: distances and redshifts galaxies: nuclei methods: data analysis techniques: image processing

UWLPIPE: Ultra-wide Bandwidth Low-frequency Pulsar data Processing Pipeline

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Research in Astronomy and Astrophysics 2024年第7期24卷 148-160页

作者： Ya-Zhou Zhang Hai-Long Zhang Jie Wang Jian Li Xin-Chen Ye Shuang-Qiang Wang Xu Du Han Wu Ting Zhang Shao-Cong Guo Xinjiang Astronomical Observatory Chinese Academy of Sciences University of Chinese Academy of Sciences Key Laboratory of Radio Astronomy Chinese Academy of Sciences National Astronomical data Center Southeast University

For real-time processing of ultra-wide bandwidth low-frequency pulsar baseband data, we designed and implemented an ultra-wide bandwidth low-frequency pulsar data processing pipeline(UWLPIPE) based on the shared ringbuffer and GPU parallel technology. UWLPIPE runs on the GPU cluster and can simultaneously receive multiple 128 MHz dual-polarization VDIF data packets preprocessed by the front-end FPGA. After aligning the dual-polarization data, multiple 128M subband data are packaged into PSRDADA baseband data or multi-channel coherent dispersion filterbank data, and multiple subband filterbank data can be spliced into wideband data after time alignment. We used the Nanshan 26 m radio telescope with the L-band receiver at964 ～ 1732 MHz to observe multiple pulsars. Finally, we processed the data using DSPSR software, and the results showed that each subband could correctly fold out the pulse profile, and the wideband pulse profile accumulated by multiple subbands could be correctly aligned.

关键词： (stars:) pulsars: general methods: data analysis techniques: miscellaneous

Statistical Properties of the Highest Pulses in Gamma-Ray Bursts

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Chinese Journal of Astronomy and Astrophysics 2003年第1期3卷 38-48页

作者： Yi-PingQin En-WeiLiang Guang-ZhongXie Cheng-YueSu NationalAstronomicalObservatories YunnanObservatoryChineseAcademyofSciencesKunming650011 NationalAstronomicalObservatories YunnanObservatoryChineseAcademyofSciencesKunming650011／／DepartmentofPhysicsGuangxiUniversityNanning530004 NationalAstronomicalObservatories YunnanObservatoryChineseAcademyofSciencesKunming650011／／DepartmentofPhysicsGuangdongIndustryUniversityGuangzhou510643

We study the statistical properties of the highest pulses within individual gamma-ray bursts (GRBs). A wavelet package analysis technique and a developed pulse-finding algorithm have been applied to identify the highest pulses from burst profiles observed by BATSE on board CGRO from 1991 April 21 to 1999 January 26. The statistical light curves of the highest pulses in four energy channels have been derived by an aligning method, which illustrate the temporal evolution of the pulse emission. Our result that narrower pulses go with higher energies is consistent with previous findings. By normalizing both the pulse durations and counts to unity, 'characteristic' profiles of the highest pulses in the four channels are also derived. The four characteristic profiles are turned out to be almost the same, thus strongly support the previous conclusion that the temporal profiles in different energy channels are self-similar and the previous conjecture on GRB pulses, implying that the emission process is similar at different energies. The cosmological time dilation effect is examined by investigating the relationship between the pulse flux and pulse duration. An anti-correlation between the two was found, which agrees with the expectation of the cosmological time dilation effect. Also, the evolution of the pulse duration with the observational epoch is studied. The result shows that the pulse duration tends to be shorter in later epochs. This trend cannot be explained by the present theoretical models, and may represent a great challenge to current theories.

关键词： gamma rays: bursts methods: data analysis

Clustering analysis of line indices for LAMOST spectra with AstroStat

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Research in Astronomy and Astrophysics 2018年第6期18卷 121-128页

作者： Shu-Xin Chen Wei-Min Sun Qi Yan College of Science Harbin Engineering University College of Mechanical and Electrical Engineering Qiqihar University

The application of data mining in astronomical surveys,such as the Large Sky Area MultiObject Fiber Spectroscopic Telescope(LAMOST)survey,provides an effective approach to automatically analyze a large amount of complex survey *** clustering could help astronomers find the associations and outliers in a big data *** this paper,we employ the k-means method to perform clustering for the line index of LAMOST spectra with the powerful software Astro *** the line index approach for analyzing astronomical spectra is an effective way to extract spectral features for low resolution spectra,which can represent the main spectral characteristics of stars.A total of 144 340 line indices for A type stars is analyzed through calculating their intra and inter distances between pairs of *** intra distance,we use the definition of Mahalanobis distance to explore the degree of clustering for each class,while for outlier detection,we define a local outlier factor for each *** Stat furnishes a set of visualization tools for illustrating the analysis *** the spectra detected as outliers,we find that most of them are problematic data and only a few correspond to rare astronomical *** show two examples of these outliers,a spectrum with abnormal continuum and a spectrum with emission *** work demonstrates that line index clustering is a good method for examining data quality and identifying rare objects.

关键词： methods: data analysis techniques: spectroscopic Astro Stat LAMOST

The north-south asymmetry of solar filaments separately at low and high latitudes in solar cycle 23

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Research in Astronomy and Astrophysics 2015年第1期15卷 77-84页

作者： De-Fang Kong Zhi-Ning Qu Qiao-Ling Guo Yunnan Observatories Chinese Academy of Sciences University of Chinese Academy of Sciences Key Laboratory of Solar Activity National Astronomical Observatories Chinese Academy of Sciences College of Mathematics Physics and Information Engineering Jiaxing University

We present the results of a study on the north-south asymmetry of solar filaments at low（〈50°） and high（〉60°） latitudes using daily filament numbers from January 1998 to November 2008（solar cycle 23）. It is found that the northern hemisphere is dominant at low latitudes for cycle 23. However, a similar asymmetry does not occur for solar filaments at high latitudes. The present study indicates that the hemispheric asymmetry of solar filaments at high latitudes in a cycle appears to have little connection with that at low latitudes. Our results support that the observed magnetic fields at high latitudes include two components： one comes from the emergence of the magnetic fields from the solar interior and the other comes from the drift of the magnetic activity at low latitudes.

关键词： Sun: activity Sun: filaments,prominences methods: data analysis

Comparison of three filters in asteroid-based autonomous navigation

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Research in Astronomy and Astrophysics 2014年第3期14卷 329-344页

作者： Wen Cui Kai-Jian Zhu State Key Laboratory of Astronautic Dynamics Xi’an Satellite Control Center

At present, optical autonomous navigation has become a key technologyin deep space exploration programs. Recent studies focus on the problem of orbit de-termination using autonomous navigation, and the choice of filter is one of the mainissues. To prepare for a possible exploration mission to Mars, the primary emphasisof this paper is to evaluate the capability of three filters, the extended Kalman filter（EKF）, unscented Kalman filter （UKF） and weighted least-squares （WLS） algorithm,which have different initial states during the cruise phase. One initial state is assumedto have high accuracy with the support of ground tracking when autonomous navi-gation is operating; for the other state, errors are set to be large without this *** addition, the method of selecting asteroids that can be used for navigation fromknown lists of asteroids to form a sequence is also presented in this study. The simula-tion results show that WLS and UKF should be the first choice for optical autonomousnavigation during the cruise phase to Mars.

关键词： celestial mechanics asteroids equation of state methods: data analysis techniques: image processing