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Research in Astronomy and Astrophysics 2021年第11期21卷 28-34页

作者： Jibrin Adejoh Alhassan Ogbonnaya Okike Augustine Ejikeme Chukwude Department of Physics and Astronomy University of NigeriaNsukka 400001Nigeria Department of Industrial Physics Ebonyi State UniversityAbakaliki 400001Nigeria

We present the results of an investigation of the relation between space-weather parameters and cosmic ray(CR)intensity modulation using algorithm-selected Forbush decreases(FDs)from Moscow(MOSC)and Apatity(APTY)neutron monitor(NM)stations during solar cycle *** FD location program detected 408 and 383 FDs from MOSC and APTY NM stations respectively.A coincident computer code employed in this work detected 229 FDs that were observed at the same Universal Time(UT)at the two *** of the 229 simultaneous FDs,we formed a subset of 139 large FDs(%)≤-4 at the MOSC *** performed a two-dimensional regression analysis between the FD magnitudes and the space-weather data on the two *** find that there were significant space-weather disturbances at the time of the CR flux *** correlation between the space-weather parameters and decreases in galactic cosmic ray(GCR)intensity at the two NM stations is statistically *** implications of the present space-weather data on CR intensity depressions are highlighted.

关键词： methods:data analysis methods:statistical Sun:coronal mass ejections(CMEs) (Sun:)solar terrestrial relations (Sun:)solar wind (ISM:)cosmic rays

Gravitational Wave Detection Based on Squeeze-and-excitation Shrinkage Networks and Multiple Detector Coherent SNR

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Research in Astronomy and Astrophysics 2022年第11期22卷 84-96页

作者： Rui-Qing Yan Wei Liu Zong-Yao Yin Rong Ma Si-Ying Chen Dan Hu Dan Wu Xian-Chuan Yu School of Artificial Intelligence Beijing Normal UniversityBeijing 100875China National Laboratory of Pattern Recognition Institute of AutomationChinese Academy of SciencesBeijing 100190China Department of Radiology and BRIC University of North Carolina at Chapel HillChapel HillNC 27599 United States of America National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China

Deep learning techniques have been applied to the detection of gravitational wave signals in the past few *** existing methods focus on the data obtained by a single ***,the signal-to-noise ratio(SNR)of gravitational wave signals in a single detector is pretty low,making it hard for deep neural networks to learn effective ***,how to use the observation signals obtained by multiple detectors in deep learning methods is a serious *** simulate binary neutron star signals from multiple detectors,including the Advanced LIGO and Virgo *** calculate coherent SNR of multiple detectors using a fully coherent allsky search method and obtain the coherent SNR data required for our proposed deep learning *** by the principle of attention network Squeeze-and-Excitation Networks(SENet)and the soft thresholding shrinkage function,we propose a novel Squeeze-and-Excitation Shrinkage(SES)module to better extract effective *** we use this module to establish a gravitational wave squeeze-and-excitation shrinkage network(GWSESNet)detection *** train and validate the performance of our model on the coherent SNR data *** model obtains satisfactory classification accuracy and can excellently complete the task of gravitational wave detection.

关键词： methods:data analysis methods:statistical gravitational waves

A simulation experiment on the GM estimation for Comet 133P/Elst-Pizarro

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Research in Astronomy and Astrophysics 2021年第1期21卷 158-164页

作者： Wu-Tong Gao Jian-Guo Yan Wei-Tong Jin Xuan Yang Chen Yang Mao Ye Fei Li Jean-Pierre Barriot l State Key Laboratory of Information Engineering in Surveying Mapping and Remote SensingWuhan UniversityWuhan 430079China China Academy of Space Technology Beijing 100094China Geodesy Observatory of Tahiti University of French PolynesiaBP 657098702 FaaaTahitiFrench Polynesia

In China’s asteroid mission to be launched around 2025,(7968)133 P/Elst-Pizarro(hereafter 133 P)will be the second target,after a visit to asteroid(469219)Kamo’*** paper describes a simulation of precise orbit determination for the spacecraft around comet 133 P,as well as estimation of its gravitational parameter(GM)value and the solar radiation pressure coefficient Cr for the *** cometocentric distances of 200,150 and 100 km orbits are considered,as well as two tracking modes:exclusive two-way range-rate mode(Earth station to spacecraft)and combinations of two-way range-rate and local spacecraft onboard ranging to the *** to exclusive two-way range-rate,the introduction of local ranging observables improves the final GM uncertainties by up to one order of *** ephemeris error in the orbit of 133 P is also considered,and we show that,to obtain a reliable estimate of the GM for 133 P,this error cannot exceed a one km range.

关键词： celestial mechanics space vehicles comets:individual(133P/Elst-Pizarro) methods:statistical

A star-based method for precise wavelength calibration of the Chinese Space Station Telescope(CSST) slitless spectroscopic survey

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Research in Astronomy and Astrophysics 2021年第3期21卷 235-242页

作者： Hai-Bo Yuan Ding-Shan Deng Yang Sun Department of Astronomy Beijing Normal UniversityBeijing 100875China

The Chinese Space Station Telescope(CSST)spectroscopic survey aims to deliver high-quality low-resolution(R>200)slitless spectra for hundreds of millions of targets down to a limiting magnitude of about 21 mag,distributed within a large survey area(17500 deg2)and covering a wide wavelength range(255-1000 nm by three bands GU,GV,and GI).As slitless spectroscopy precludes the usage of wavelength calibration lamps,wavelength calibration is one of the most challenging issues in the reduction of slitless spectra,yet it plays a key role in measuring precise radial velocities of stars and redshifts of *** this work,we propose a star-based method that can monitor and correct for possible errors in the CSST wavelength calibration using normal scientific observations,taking advantage of the facts that(ⅰ)there are about ten million stars with reliable radial velocities now available thanks to spectroscopic surveys like LAMOST,(ⅱ)the large field of view of CSST enables efficient observations of such stars in a short period of time,and(ⅲ)radial velocities of such stars can be reliably measured using only a narrow segment of CSST *** demonstrate that it is possible to achieve a wavelength calibration precision of a few km s^(-1) for the GU band,and about 10 to 20 kms^(-1) for the GV and GI bands,with only a few hundred velocity standard *** of the method to other surveys are also discussed.

关键词： methods:data analysis methods:statistical techniques:spectroscopic techniques:radial velocities stars:fundamental parameters stars:kinematics and dynamics

Searching for AGN and pulsar candidates in 4FGL unassociated sources using machine learning

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Research in Astronomy and Astrophysics 2021年第1期21卷 143-157页

作者： Ke-Rui Zhu Shi-Ju Kang Yong-Gang Zheng Department of Physics Yunnan Normal UniversityKunmingYunnan650092China School of Physics and Electrical Engineering Liupanshui Normal UniversityLiupanshuiGuizhou553004China

In the fourth Fermi Large Area Telescope source catalog(4 FGL),5064γ-ray sources are reported,including 3207 active galactic nuclei(AGNs),239 pulsars,1336 unassociated sources,92 sources with weak association with blazars at low Galactic latitudes and 190 other *** employ two different supervised machine learning classifiers,combined with the direct observation parameters given by the 4 FGL fits table,to search for sources potentially classified as AGNs and pulsars in the 1336 unassociated *** order to reduce the error caused by the large difference in the sizes of samples,we divide the classification process into two separate steps in order to identify the AGNs and the ***,we select the identified AGNs from all of the samples,and then select the identified pulsars from the remaining *** the 4 FGL sources associated or identified as AGNs,pulsars and other sources with the features selected through the K-S test and the random forest(RF)feature importance measurement,we trained,optimized and tested our classifier ***,the models are applied to classify the 1336 unassociated *** to the calculation results of the two classifiers,we report the sensitivity,specificity,accuracy in each step and the class of unassociated sources given by each *** accuracy obtained in the first step is approximately 9595%;in the second step,the obtained overall accuracy is approximately 80%.Combining the results of the two classifiers,we predict that there are 583 AGN-type candidates,115 pulsar-type candidates,154 other types ofγ-ray candidates and 484 of uncertain types.

关键词： gamma rays:galaxies galaxies:active methods:statistical

Study of the Modified Gaussian Model on olivine diagnostic spectral features and its applications in space weathering experiments

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Research in Astronomy and Astrophysics 2020年第8期20卷 261-279页

作者： Hui-Jie Han Xiao-Ping Lu Ya-Zhou Yang Hao Zhang Admire Muchimamui Mutelo State Key Laboratory of Lunar and Planetary Sciences Macao University of Science and TechnologyTaipa 999078MacaoChina State Key Laboratory of Space Weather National Space Science CenterChinese Academy of SciencesBeijing 100190China Planetary Science Institute School of Earth SciencesChina University of GeosciencesWuhan 430074China CAS Center for Excellence in Comparative Planetology Hefei 230026China School of Earth Science and Resources China University of GeosciencesBeijing 100083China

The absorption features of olivine in visible and near-infrared(VNIR)reflectance spectra are the key spectral parameters in its mineralogical ***,these spectral parameters can be obtained by exploiting the Modified Gaussian Model(MGM)with a proper continuum ***,different continua may change the deconvolution results of these *** paper investigates the diagnostic spectral features of olivine with diverse chemical *** different continuum removal methods with MGM for getting the deconvolution results are presented and the regression equations for predicting the Mg-number(Fo#)are *** results show that different continua superimposed on the mineral absorption features will make the absorption center shift,as well as the obvious alterations in shape,width and strength of the absorption ***,it is also found that the logarithm of a second-order polynomial continuum can match the overall shape of the spectrum in logarithmic space,and the improved regression equations applied to estimate the chemical composition of olivine-dominated spectra also have a better *** an application example,the improved approach is applied to pulse laser irradiated olivine grains to simulate and study the space weathering effects on olivine diagnostic spectral *** experiments confirm that space weathering can make the absorption band center shift toward longer ***,the Fo#estimated from remote sensing spectra may be less than its actual chemical *** results may provide valuable information for revealing the difference between the spectra of olivine grains and olivine-dominated asteroids.

关键词： techniques:spectroscopic instrumentation:spectrographs methods:statistical minor planets asteroids:general

Stellar spectral classification and feature evaluation based on a random forest

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Research in Astronomy and Astrophysics 2019年第8期19卷 56-62页

作者： Xiang-Ru Li Yang-Tao Lin Kai-Bin Qiu School of Mathematical Sciences South China Normal University

With the availability of multi-object spectrometers and the design and operation of some large scale sky surveys, the issue of how to deal with enormous quantities of spectral data efficiently and accurately is becoming more and more important. This work investigates the classification problem of stellar spectra under the assumption that there is no perfect absolute flux calibration, for example, when considering spectra from the Guo Shou Jing Telescope(the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, LAMOST). The proposed scheme consists of the following two procedures: Firstly, a spectrum is normalized based on a 17 th order polynomial fitting;secondly, a random forest(RF) is utilized to classify the stellar spectra. Experiments on four stellar spectral libraries show that the RF has good classification performance. This work also studied the spectral feature evaluation problem based on RF. The evaluation is helpful in understanding the results of the proposed stellar classification scheme and exploring its potential improvements in the future.

关键词： methods:statistical methods:data analysis virtual observatory tools

Estimating the power spectrum of a discrete cosmic momentum field with fast Fourier transform

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Research in Astronomy and Astrophysics 2020年第9期20卷 253-267页

作者： Jun Pan National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China

Fast Fourier transform based estimators are formulated for measuring momentum power spectra,including the auto power spectra of the momentum,the momentum divergence,and the cross spectrum of density fluctuation and momentum *** using the third order Bettle-Lemariéscaling function to assign discrete objects to regular grids for fast Fourier transform are proposed to clean alias *** experiments prove that the implementation can achieve sub-percent precision till close to the Nyquist *** impact of removing bulk flow on the estimation of momentum power spectra is derived theoretically and verified *** bulk flow has little effects at large scales but might induce meaningful differences in nonlinear regime,and probably it is not necessary to subtract bulk flow for samples which peculiar velocities are exact or sufficiently *** power spectra of dark matter samples from N-body simulation are measured and *** expected,the prediction of the one loop Eulerian perturbation theory agrees with simulation only slightly better than the linear theory at z=0,but can be applied to higher redshift with improved *** of simulation data and the one loop Eulerian theory both reveal that the momentum field contains strong rotational part,and there is a large stochastic component in the divergence of momentum which is not correlated with the density *** three kinds of momentum power spectra have their own characteristics.

关键词： large scale structure of Universe cosmology:theory methods:numerical methods:statistical

The Electromagnetic Compatibility between FAST and Public Mobile Communication Stations and its Cognitive Using Frequency Strategy

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Research in Astronomy and Astrophysics 2022年第12期22卷 183-197页

作者： Jian Wang Yi-Bo Zhao Ya-Fei Shi Cheng Yang Yu-Long Hao Jian-Min Sun School of Microelectronics Tianjin UniversityTianjin 300072China Qingdao Institute for Ocean Technology Tianjin UniversityQingdao 266200China Guizhou Radio Monitoring Station Guiyang 550005China

To master the electromagnetic environment characteristics around the Five-hundred-meter Aperture Spherical radio Telescope(FAST)and ensure a better ecological environment in the radio-quiet zone of FAST,we analyzed the radiation characteristics of the public communication stations around *** comparing the FAST received signal power from the communication stations and the interference protection threshold of the radio astronomy applications,we found that the total proportion of the communication stations exceeding the radio astronomy protection threshold is 69.01%.Furthermore,to fully protect the regular operation of FAST,we proposed four interference avoidance and frequency coordination strategies based on the cognitive ***:(1)increasing the operating frequency of the communication station;(2)adjusting the direction of the transmitter antennas;(3)reducing the height of the transmitter antennas;(4)decreasing the transmitting power of the communication *** a result,the impact on FAST can effectively be reduced,and the FAST's received power from the communication stations will be lower than the radio astronomy protection threshold by using the above mentioned four *** the analysis of the experiment,the prediction is consistent with the overall trend of the measurement,and using frequency strategies can significantly reduce the signal power at the receiving ***,we construct a quality evaluation system for frequency coordination and analyze the satisfaction of the four strategies under the four *** results show that adjusting the direction of the transmitter antennas has better satisfaction,and the maximum satisfaction is *** above research results can be further expanded to potentially improve the electromagnetic ecological environment around FAST and support the regular operation of FAST.

关键词： methods:analytical methods:statistical telescopes

BoxCox multi-output linear regression for 10.7 cm solar radio flux prediction

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Research in Astronomy and Astrophysics 2021年第4期21卷 225-234页

作者： Rui-Fei Cui Ya-Guang Zhu Huan Zhang Ri-Wei Zhang Hong-Yu Zhao Zheng-Lian Li State Key Laboratory of Astronautic Dynamics Xi’an 710043China Beijing Information and Communication Research Center Beijing 100840China

We consider the problem of predicting the mid-term daily 10.7 cm solar radio flux(F10.7),a widely-used solar activity index.A novel approach is proposed for this task,in which BoxCox transformation with a proper parameter is first applied to make the data satisfy the property of homoscedasticity that is a basic assumption of regression models,and then a multi-output linear regression model is used to predict future F10.7 *** experiment shows that the BoxCox transformation significantly improves the predictive performance and our new approach works substantially better than the prediction from the US Airforce and other alternative methods like Auto-regressive Model,Multi-layer Perceptron,and Support Vector Regression.

关键词： Sun:radio radiation methods:data analysis methods:statistical