Pub Date : 2023-12-07DOI: 10.1088/1674-4527/ad1367
Xu Zhang, Bin Zhang
In this paper, new light curves (LCs) of contact eclipsing binary (CEB) systems LX Lyn and V0853 Aur are presented and analysed by using the 2015 version of the Wilson-Devinney (W-D) code. In order to explain the asymmetric LCs of them, cool star-spots on the components were employed. It is suggested that the fill-out degree of them are f=12.0% (LX Lyn) and f=26.3% (V0853 Aur), respectively. At the same time, we found that LX Lyn is a W-type eclipsing binary (EB) with an orbital inclination of $i=84.88^{circ}$ and a mass ratio of $q=2.31$. V0853 Aur is also a W-type CEB with a mass ratio of $q=2.77$ and an orbital inclination of $i$=$79.26^{circ}$. Based on all available times of light minimum, the orbital period changes of them are studied by using the $O-C$ method. The $O-C$ diagram of LX Lyn reveals a cyclic oscillation with a period about 14.84 years and an amplitude of 0.0019 days, which can be explained by the light-travel time effect (LTTE) due to the presence of a third body with a minimum mass of 0.06$M_odot$. For V0853 Aur, it is discovered that the $O-C$ diagram of the system also shows a cyclic oscillation with a period of 9.64 years and an amplitude of 0.03365 days. The cyclic oscillation of V0853 Aur can be attributed to the LTTE by means of a third body with a mass no less than 3.77$M_odot$. The third body may play an important role in the formation and evolution of these systems.
{"title":"Periodic Variation Studies of the Two Short Period W UMa-type Eclipsing Binaries: LX Lyn and V0853 Aur","authors":"Xu Zhang, Bin Zhang","doi":"10.1088/1674-4527/ad1367","DOIUrl":"https://doi.org/10.1088/1674-4527/ad1367","url":null,"abstract":"\u0000 In this paper, new light curves (LCs) of contact eclipsing binary (CEB) systems LX Lyn and V0853 Aur are presented and analysed by using the 2015 version of the Wilson-Devinney (W-D) code. In order to explain the asymmetric LCs of them, cool star-spots on the components were employed. It is suggested that the fill-out degree of them are f=12.0% (LX Lyn) and f=26.3% (V0853 Aur), respectively. At the same time, we found that LX Lyn is a W-type eclipsing binary (EB) with an orbital inclination of $i=84.88^{circ}$ and a mass ratio of $q=2.31$. V0853 Aur is also a W-type CEB with a mass ratio of $q=2.77$ and an orbital inclination of $i$=$79.26^{circ}$. Based on all available times of light minimum, the orbital period changes of them are studied by using the $O-C$ method. The $O-C$ diagram of LX Lyn reveals a cyclic oscillation with a period about 14.84 years and an amplitude of 0.0019 days, which can be explained by the light-travel time effect (LTTE) due to the presence of a third body with a minimum mass of 0.06$M_odot$. For V0853 Aur, it is discovered that the $O-C$ diagram of the system also shows a cyclic oscillation with a period of 9.64 years and an amplitude of 0.03365 days. The cyclic oscillation of V0853 Aur can be attributed to the LTTE by means of a third body with a mass no less than 3.77$M_odot$. The third body may play an important role in the formation and evolution of these systems.","PeriodicalId":54494,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"17 12","pages":""},"PeriodicalIF":1.8,"publicationDate":"2023-12-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138592794","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-07DOI: 10.1088/1674-4527/ad1366
Jiao Zheng, Peng-fei Zhang, Li Zhang
Recently, a new radio millisecond pulsar (MSP) J1740–5340B, hosted in the globu- lar cluster NGC 6397, was reported with a spin period 5.78 ms in an eclipsing binary system with an orbital period of 1.97 day. Based on a modified radio ephemeris updated by tool tempo2, we analyze the ∼15 year γ-ray data obtained from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope and detect PSR J1740−5340B’s γ-ray pulsation at a confidence level of ∼4σ with a weighted H-test value of ∼26. By performing a phase-resolved analysis, the γ-ray luminosity in on-pulse interval of PSR J1740–5340B is Lγ ∼ 3.8 × 1033 erg/s using the NGC 6397’s distance of 2.48 kpc. And γ-rays from the on-pulse part of PSR J1740−5340B contribute ∼90% of the total observed γ-ray emissions from NGC 6397. No significant γ-ray pulsation of another MSP J1740–5340A in the GC is detected. Considering that the previous four cases of MSPs in GCs, more data in γ-ray, X-ray, and radio are encouraged to finally confirm the γ-ray emissions from MSP J1740−5340B, especially starving for a precise ephemeris.
{"title":"A Possible γ-ray Pulsation from PSR J1740−5340B in the Globular Cluster NGC 6397","authors":"Jiao Zheng, Peng-fei Zhang, Li Zhang","doi":"10.1088/1674-4527/ad1366","DOIUrl":"https://doi.org/10.1088/1674-4527/ad1366","url":null,"abstract":"\u0000 Recently, a new radio millisecond pulsar (MSP) J1740–5340B, hosted in the globu- lar cluster NGC 6397, was reported with a spin period 5.78 ms in an eclipsing binary system with an orbital period of 1.97 day. Based on a modified radio ephemeris updated by tool tempo2, we analyze the ∼15 year γ-ray data obtained from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope and detect PSR J1740−5340B’s γ-ray pulsation at a confidence level of ∼4σ with a weighted H-test value of ∼26. By performing a phase-resolved analysis, the γ-ray luminosity in on-pulse interval of PSR J1740–5340B is Lγ ∼ 3.8 × 1033 erg/s using the NGC 6397’s distance of 2.48 kpc. And γ-rays from the on-pulse part of PSR J1740−5340B contribute ∼90% of the total observed γ-ray emissions from NGC 6397. No significant γ-ray pulsation of another MSP J1740–5340A in the GC is detected. Considering that the previous four cases of MSPs in GCs, more data in γ-ray, X-ray, and radio are encouraged to finally confirm the γ-ray emissions from MSP J1740−5340B, especially starving for a precise ephemeris.","PeriodicalId":54494,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"12 4","pages":""},"PeriodicalIF":1.8,"publicationDate":"2023-12-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138592817","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-06DOI: 10.1088/1674-4527/ad12fb
Yi-jia Zheng
In observational cosmology, Supernova Ia is used as a standard candle in order to extend the Hubble diagram to a higher redshift range. Astrophysicists found that the observed brightness of high redshift supernovae Ia is dimmer than expected. This dimming effect is considered observational evidence for the existence of dark energy in the universe. It should be noted that this conclusion is based on an assumption that the mass density of the cosmic plasma is very small. Therefore, the dimming effect caused by the Compton scattering of free electrons in cosmic plasma can be neglected. X-Ray observations suggest that the mass density of the cosmic plasma may be very large. In theory, the observed dimming effect of high redshift supernovae Ia may be caused by the Compton scattering of free electrons in the cosmic plasma. In this paper it will be shown that this idea is reasonable. Therefore, there is no need to introduce the confusing concept of dark energy into cosmology.
{"title":"Effect of cosmic plasma on the observation of Supernovae Ia","authors":"Yi-jia Zheng","doi":"10.1088/1674-4527/ad12fb","DOIUrl":"https://doi.org/10.1088/1674-4527/ad12fb","url":null,"abstract":"\u0000 In observational cosmology, Supernova Ia is used as a standard candle in order to extend the Hubble diagram to a higher redshift range. Astrophysicists found that the observed brightness of high redshift supernovae Ia is dimmer than expected. This dimming effect is considered observational evidence for the existence of dark energy in the universe. It should be noted that this conclusion is based on an assumption that the mass density of the cosmic plasma is very small. Therefore, the dimming effect caused by the Compton scattering of free electrons in cosmic plasma can be neglected. X-Ray observations suggest that the mass density of the cosmic plasma may be very large. In theory, the observed dimming effect of high redshift supernovae Ia may be caused by the Compton scattering of free electrons in the cosmic plasma. In this paper it will be shown that this idea is reasonable. Therefore, there is no need to introduce the confusing concept of dark energy into cosmology.","PeriodicalId":54494,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"46 6","pages":""},"PeriodicalIF":1.8,"publicationDate":"2023-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138595326","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-05DOI: 10.1088/1674-4527/ad12a7
Lin-Hong Wang, Qian-Heng Nie, Kun Wang, Xiaodian Chen, Chunguang Zhang, Licai Deng, Xiaobin Zhang, Tian-Lu Chen
Open clusters are the basic building blocks that serve as an the laboratory for the study of young stellar populations in the Milky Way. Variable stars in open clusters provide a unique way to accurately probe the internal structure, temporal and dynamical evolutionary stages of individual stars and the host cluster. The most powerful tool for such studies is time-domain photometric observations. This paper follows the route of our previous work, concentrating on a photometric search for variable stars in NGC 884. The target cluster is the companion of NGC 869, forming the well-known double cluster system that is gravitationally bound. From the observation run in November 2016, a total of 9247 B-band CCD images and 8218 V-band CCD images were obtained. We detected a total of 15 stars with variability in visual brightness, including 5 Be stars, 3 eclipsing binaries, and 7 of unknown type. Two new variable stars were discovered in this work. We also compared the variable star content of NGC 884 with its companion NGC 869.
{"title":"Variable stars in the 50BiN open cluster survey. III. NGC 884","authors":"Lin-Hong Wang, Qian-Heng Nie, Kun Wang, Xiaodian Chen, Chunguang Zhang, Licai Deng, Xiaobin Zhang, Tian-Lu Chen","doi":"10.1088/1674-4527/ad12a7","DOIUrl":"https://doi.org/10.1088/1674-4527/ad12a7","url":null,"abstract":"\u0000 Open clusters are the basic building blocks that serve as an the laboratory for the study of young stellar populations in the Milky Way. Variable stars in open clusters provide a unique way to accurately probe the internal structure, temporal and dynamical evolutionary stages of individual stars and the host cluster. The most powerful tool for such studies is time-domain photometric observations. This paper follows the route of our previous work, concentrating on a photometric search for variable stars in NGC 884. The target cluster is the companion of NGC 869, forming the well-known double cluster system that is gravitationally bound. From the observation run in November 2016, a total of 9247 B-band CCD images and 8218 V-band CCD images were obtained. We detected a total of 15 stars with variability in visual brightness, including 5 Be stars, 3 eclipsing binaries, and 7 of unknown type. Two new variable stars were discovered in this work. We also compared the variable star content of NGC 884 with its companion NGC 869.","PeriodicalId":54494,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"124 14","pages":""},"PeriodicalIF":1.8,"publicationDate":"2023-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138599481","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-02DOI: 10.1088/1674-4527/ad1223
Kaifeng Yu, S. Zuo, Fengquan Wu, Yougang Wang, Xuelei Chen
The Tianlai cylinder pathfinder is a radio interferometer array to test 21 cm intensity mapping techniques in the post-reionization era. It works in passive drift scan mode to survey the sky visible in the northern hemisphere. To deal with the large instantaneous field of view and the spherical sky, we decompose the drift scan data into $m$-modes, which are linearly related to the sky intensity. The sky map is reconstructed by solving the linear interferometer equations. Due to incomplete $uv$ coverage of the interferometer baselines, this inverse problem is usually ill-posed, and regularization method is needed for its solution. In this paper, we use simulation to investigate two frequently used regularization methods, the Truncated Singular Value Decomposition (TSVD), and the Tikhonov regularization techniques. Choosing the regularization parameter is very important for its application. We employ the generalized cross validation (GCV) method and the L-curve method to determine the optimal value. We compare the resulting maps obtained with the different regularization methods, and for the different parameters derived using the different criteria. While both methods can yield good maps for a range of regularization parameters, in the Tikhonov method the suppression of noisy modes are more gradually applied, produce more smooth maps which avoids some visual artefacts in the maps generated with the TSVD method.
{"title":"Application of Regularization Methods in the Sky Map Reconstruction of the Tianlai Cylinder Pathfinder Array","authors":"Kaifeng Yu, S. Zuo, Fengquan Wu, Yougang Wang, Xuelei Chen","doi":"10.1088/1674-4527/ad1223","DOIUrl":"https://doi.org/10.1088/1674-4527/ad1223","url":null,"abstract":"\u0000 The Tianlai cylinder pathfinder is a radio interferometer array to test 21 cm intensity mapping techniques in the post-reionization era. It works in passive drift scan mode to survey the sky visible in the northern hemisphere. To deal with the large instantaneous field of view and the spherical sky, we decompose the drift scan data into $m$-modes, which are linearly related to the sky intensity. The sky map is reconstructed by solving the linear interferometer equations. Due to incomplete $uv$ coverage of the interferometer baselines, this inverse problem is usually ill-posed, and regularization method is needed for its solution. In this paper, we use simulation to investigate two frequently used regularization methods, the Truncated Singular Value Decomposition (TSVD), and the Tikhonov regularization techniques. Choosing the regularization parameter is very important for its application. We employ the generalized cross validation (GCV) method and the L-curve method to determine the optimal value. We compare the resulting maps obtained with the different regularization methods, and for the different parameters derived using the different criteria. While both methods can yield good maps for a range of regularization parameters, in the Tikhonov method the suppression of noisy modes are more gradually applied, produce more smooth maps which avoids some visual artefacts in the maps generated with the TSVD method.","PeriodicalId":54494,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"70 5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2023-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138606613","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-13DOI: 10.1088/1674-4527/ad0c27
xiong Shao Guo, Chao Zhai
Abstract With the development of cutting-edge multi-object spectrographs, fiber positioners located in focal plane are being scaled down in size, and miniature hollow-cup Permanent Magnet motors are now being considered as a suitable replacement for Faulhaber Precistep stepper motors. However, the small electrical time constant of such coreless motors poses a challenge, as the problem of severe commutation torque ripple in a fiber positioner running a position loop has been tricky. To overcome this challenge, it is advised to increase the Pulse Width Modulation frequency as much as possible to mitigate the effects of the current fluctuation. This must be done while ensuring adequate resolution of the PWM generator. By employing a voltage Open-loop Field-oriented control based on a modulation frequency of 1MHz, the drive current only costs 25mA under a 3.3V power supply. The sine degree of phase current is immaculate, and the repeat positioning accuracy can reach 2um. Moreover, it is possible to further shrink the bill of devices and the layout area of the Printed Circuit Board, especially in size-sensitive applications. This device has been developed under the new generation of The Large Sky Area Multi-Object Fiber Spectroscopic Telescope.
{"title":"The Application of Permanent Magnet Synchronous Motor with Small Electrical Time Constant in Fiber Positioner","authors":"xiong Shao Guo, Chao Zhai","doi":"10.1088/1674-4527/ad0c27","DOIUrl":"https://doi.org/10.1088/1674-4527/ad0c27","url":null,"abstract":"Abstract With the development of cutting-edge multi-object spectrographs, fiber positioners located in focal plane are being scaled down in size, and miniature hollow-cup Permanent Magnet motors are now being considered as a suitable replacement for Faulhaber Precistep stepper motors. However, the small electrical time constant of such coreless motors poses a challenge, as the problem of severe commutation torque ripple in a fiber positioner running a position loop has been tricky. To overcome this challenge, it is advised to increase the Pulse Width Modulation frequency as much as possible to mitigate the effects of the current fluctuation. This must be done while ensuring adequate resolution of the PWM generator. By employing a voltage Open-loop Field-oriented control based on a modulation frequency of 1MHz, the drive current only costs 25mA under a 3.3V power supply. The sine degree of phase current is immaculate, and the repeat positioning accuracy can reach 2um. Moreover, it is possible to further shrink the bill of devices and the layout area of the Printed Circuit Board, especially in size-sensitive applications. This device has been developed under the new generation of The Large Sky Area Multi-Object Fiber Spectroscopic Telescope.","PeriodicalId":54494,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"58 6","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136281623","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-13DOI: 10.1088/1674-4527/ad0c28
Yi Zi You, YunRong Pan, Zhi Ma, Li Zhang, Shuo Xiao, Dan Dan Zhang, Shijun Dang, Shuang Ru Zhao, Pei Wang, Ai-Jun Dong, Jiatao Jiang, Jibing Leng, Weian Li, Siyao Li
Abstract Pulsar search is always the basis of pulsar navigation, gravitational wave detection and other research topics. Currently, the volume of pulsar candidates collected by Five-hundred-meter Aperture Spherical radio Telescope (FAST) shows an explosive growth rate that has brought challenges for its pulsar candidate filtering System. Particularly, the multi-view heterogeneous data and class imbalance between true pulsars and non-pulsar candidates have negative effects on traditional single-modal supervised classification methods. In this study, a multi-modal and semi-supervised learning based pulsar candidate sifting algorithm is presented, which adopts a hybrid ensemble clustering scheme of density-based and partition-based methods combined with a feature-level fusion strategy for input data and a data partition strategy for parallelization. Experiments on both HTRU (The High Time Resolution Universe Survey) 2 and FAST actual observation data demonstrate that the proposed algorithm could excellently identify the pulsars: On HTRU2, the precision and recall rates of its parallel mode reach 0.981 and 0.988. On FAST data, those of its parallel mode reach 0.891 and 0.961, meanwhile, the running time also significantly decrease with the increment of parallel nodes within limits. So, we can get the conclusion that our algorithm could be a feasible idea for large scale pulsar candidate sifting of FAST drift scan observation.
脉冲星搜索一直是脉冲星导航、引力波探测等研究课题的基础。目前，500米口径球面射电望远镜(FAST)采集的候选脉冲星数量呈爆发式增长，这给其候选脉冲星过滤系统带来了挑战。特别是，真实脉冲星和非脉冲星候选星之间的多视点异构数据和类别不平衡对传统的单模态监督分类方法产生了不利影响。本文提出了一种基于多模态半监督学习的脉冲星候选筛选算法，该算法采用基于密度和基于分区的混合集成聚类方案，并结合输入数据的特征级融合策略和并行化的数据分区策略。在HTRU2 (High Time Resolution Universe Survey)和FAST实际观测数据上的实验表明，该算法能够很好地识别脉冲星:在HTRU2上，其并行模式的准确率和召回率分别达到0.981和0.988。在FAST数据上，其并行模式的运行时间分别达到0.891和0.961，同时在一定范围内，随着并行节点的增加，运行时间也显著减少。由此可以得出结论，该算法对于FAST漂移扫描观测的大规模候选脉冲星筛选是一种可行的思路。
{"title":"Applying hybrid clustering in pulsar candidate sifting with multi-modality for FAST survey","authors":"Yi Zi You, YunRong Pan, Zhi Ma, Li Zhang, Shuo Xiao, Dan Dan Zhang, Shijun Dang, Shuang Ru Zhao, Pei Wang, Ai-Jun Dong, Jiatao Jiang, Jibing Leng, Weian Li, Siyao Li","doi":"10.1088/1674-4527/ad0c28","DOIUrl":"https://doi.org/10.1088/1674-4527/ad0c28","url":null,"abstract":"Abstract Pulsar search is always the basis of pulsar navigation, gravitational wave detection and other research topics. Currently, the volume of pulsar candidates collected by Five-hundred-meter Aperture Spherical radio Telescope (FAST) shows an explosive growth rate that has brought challenges for its pulsar candidate filtering System. Particularly, the multi-view heterogeneous data and class imbalance between true pulsars and non-pulsar candidates have negative effects on traditional single-modal supervised classification methods. In this study, a multi-modal and semi-supervised learning based pulsar candidate sifting algorithm is presented, which adopts a hybrid ensemble clustering scheme of density-based and partition-based methods combined with a feature-level fusion strategy for input data and a data partition strategy for parallelization. Experiments on both HTRU (The High Time Resolution Universe Survey) 2 and FAST actual observation data demonstrate that the proposed algorithm could excellently identify the pulsars: On HTRU2, the precision and recall rates of its parallel mode reach 0.981 and 0.988. On FAST data, those of its parallel mode reach 0.891 and 0.961, meanwhile, the running time also significantly decrease with the increment of parallel nodes within limits. So, we can get the conclusion that our algorithm could be a feasible idea for large scale pulsar candidate sifting of FAST drift scan observation.","PeriodicalId":54494,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"58 13","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136281760","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-13DOI: 10.1088/1674-4527/ad0c26
Haitao Lin, Xiangru Li
Abstract Pulsar detection has become an active research topic in radio astronomy recently. One of the essential procedures for pulsar detection is pulsar candidate sifting (PCS), a procedure of find out the potential pulsar signals in a survey. However, pulsar candidates are always class-imbalanced, as most candidates are non-pulsars such as RFI and only a tiny part of them are from real pulsars. Class imbalance has greatly damaged the performance of machine learning (ML) models, resulting in a heavy cost as some real pulsars are misjudged.
To deal with the problem, techniques of choosing relevant features to discriminate pulsars from non-pulsars are focused on, which is known as {itshape feature selection}. Feature selection is a process of selecting a subset of the most relevant features from a feature pool. The distinguishing features between pulsars and non-pulsars can significantly improve the performance of the classifier even if the data are highly imbalanced.
In this work, an algorithm of feature selection called K-fold Relief-Greedy algorithm (KFRG) is designed. KFRG is a two-stage algorithm. In the first stage, it filters out some irrelevant features according to their K-fold Relief scores, while in the second stage, it removes the redundant features and selects the most relevant features by a forward greedy search strategy. Experiments on the dataset of the High Time Resolution Universe survey verified that ML models based on KFRG are capable for PCS, correctly separating pulsars from non-pulsars even if the candidates are highly class-imbalanced.
{"title":"Dealing with the data imbalance problem on pulsar candidates sifting based on feature selection","authors":"Haitao Lin, Xiangru Li","doi":"10.1088/1674-4527/ad0c26","DOIUrl":"https://doi.org/10.1088/1674-4527/ad0c26","url":null,"abstract":"Abstract Pulsar detection has become an active research topic in radio astronomy recently. One of the essential procedures for pulsar detection is pulsar candidate sifting (PCS), a procedure of find out the potential pulsar signals in a survey. However, pulsar candidates are always class-imbalanced, as most candidates are non-pulsars such as RFI and only a tiny part of them are from real pulsars. Class imbalance has greatly damaged the performance of machine learning (ML) models, resulting in a heavy cost as some real pulsars are misjudged.
To deal with the problem, techniques of choosing relevant features to discriminate pulsars from non-pulsars are focused on, which is known as {itshape feature selection}. Feature selection is a process of selecting a subset of the most relevant features from a feature pool. The distinguishing features between pulsars and non-pulsars can significantly improve the performance of the classifier even if the data are highly imbalanced.
In this work, an algorithm of feature selection called K-fold Relief-Greedy algorithm (KFRG) is designed. KFRG is a two-stage algorithm. In the first stage, it filters out some irrelevant features according to their K-fold Relief scores, while in the second stage, it removes the redundant features and selects the most relevant features by a forward greedy search strategy. Experiments on the dataset of the High Time Resolution Universe survey verified that ML models based on KFRG are capable for PCS, correctly separating pulsars from non-pulsars even if the candidates are highly class-imbalanced.","PeriodicalId":54494,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"58 12","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136281761","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-10DOI: 10.1088/1674-4527/ad0b86
Bing-qing Zhang, Hong Wu, Wei Du, pinsong zhao, Min He, Feng-Jie Lei
Abstract We present a study of low surface brightness galaxies (LSBGs) selection by fitting the images for all the galaxies in α.40 SDSS DR7 sample with two kinds of single-component model and two kinds of two-component model (disk+bulge): single exponential, single sérsic, exponential+deVaucular (exp+deV), and exponential+sérsic (exp+ser). Under the criteria of the B band disk central surface brightness µ0,disk(B) ⩾ 22.5 mag arcsec−2 and the axis ratio b/a > 0.3, we selected four none-edge-on LSBG samples from each of the models which contains 1105, 1038, 207, and 75 galaxies, respectively. There are 756 galaxies in common between LSBGs selected by exponential and sérsic models, corresponding to 68.42% of LSBGs selected by exponential model and 72.83% of LSBGs selected by sérsic model, the rest of the discrepancy is due to the difference in obtaining µ0 between the exponential and sérsic models. Based on the fitting, in the range of 0.5 ≤ n ≤ 1.5, the relation of µ0 from two models can be written as µ0,sersic − µ0,exp = −1.345(n − 1). The LSBGs selected by disk+bulge models (LSBG_2comps) are more massive than LSBGs selected by single-component models (LSBG_1comp), and also show a larger disk component. Though the bulges in the majority of our LSBG_2comps are not prominent, more than 60% of our LSBG_2comps will not be selected if we adopt a single-component model only. We also identified 31 giant low surface brightness galaxies (gLSBGs) from LSBG_2comps. They locate at the same region in the color-magnitude diagram as other gLSBGs. After we compared different criteria of gLSBGs selection, we find that for gas-rich LSBGs, M⋆ > 1010M⊙ is the best to distinguish between gLSBGs and normal LSBGs with bulge.
{"title":"Low Surface Brightness Galaxies selected by different model fitting","authors":"Bing-qing Zhang, Hong Wu, Wei Du, pinsong zhao, Min He, Feng-Jie Lei","doi":"10.1088/1674-4527/ad0b86","DOIUrl":"https://doi.org/10.1088/1674-4527/ad0b86","url":null,"abstract":"Abstract We present a study of low surface brightness galaxies (LSBGs) selection by fitting the images for all the galaxies in α.40 SDSS DR7 sample with two kinds of single-component model and two kinds of two-component model (disk+bulge): single exponential, single sérsic, exponential+deVaucular (exp+deV), and exponential+sérsic (exp+ser). Under the criteria of the B band disk central surface brightness µ0,disk(B) ⩾ 22.5 mag arcsec−2 and the axis ratio b/a > 0.3, we selected four none-edge-on LSBG samples from each of the models which contains 1105, 1038, 207, and 75 galaxies, respectively. There are 756 galaxies in common between LSBGs selected by exponential and sérsic models, corresponding to 68.42% of LSBGs selected by exponential model and 72.83% of LSBGs selected by sérsic model, the rest of the discrepancy is due to the difference in obtaining µ0 between the exponential and sérsic models. Based on the fitting, in the range of 0.5 ≤ n ≤ 1.5, the relation of µ0 from two models can be written as µ0,sersic − µ0,exp = −1.345(n − 1). The LSBGs selected by disk+bulge models (LSBG_2comps) are more massive than LSBGs selected by single-component models (LSBG_1comp), and also show a larger disk component. Though the bulges in the majority of our LSBG_2comps are not prominent, more than 60% of our LSBG_2comps will not be selected if we adopt a single-component model only. We also identified 31 giant low surface brightness galaxies (gLSBGs) from LSBG_2comps. They locate at the same region in the color-magnitude diagram as other gLSBGs. After we compared different criteria of gLSBGs selection, we find that for gas-rich LSBGs, M⋆ > 1010M⊙ is the best to distinguish between gLSBGs and normal LSBGs with bulge.","PeriodicalId":54494,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"80 20","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135091597","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract In celestial source detection in Tianlai project, locating interferometric fringe in visibility data accurately will influence downstream tasks drastically, such as physical parameters estimation and weak celestial source exploration. Considering that traditional locating methods are time-consuming and supervised methods require a great quantity of expensive labeled data, in this paper, we firstly investigate characteristic of interferometric fringes in simulation and real scenario respectively, and integrate almost parameter-free unsupervised clustering method and seeding filling or eraser algorithm to propose a hierarchical plug and play method to improve locating accuracy. Then, we apply our method to locate single and multiple sources' interferometric fringes in simulation data. Next, we apply our method in real data taken from Tianlai radio telescope array. Finally, we do comparison with unsupervised methods of state of the art. These results show that our method has robustness in different scenarios and can improve locating measurement accuracy effectively.
{"title":"A Hierarchical Method for Locating the Interferometric Fringes of Celestial Sources in the Visibility Data","authors":"Rong Ma, Ruiqing Yan, Hanshuai Cui, Xiaochun Cheng, Jixia Li, Fengquan Wu, Zongyao Yin, Hao Wang, Wenyi Zeng, Xianchuan Yu","doi":"10.1088/1674-4527/ad0b85","DOIUrl":"https://doi.org/10.1088/1674-4527/ad0b85","url":null,"abstract":"Abstract In celestial source detection in Tianlai project, locating interferometric fringe in visibility data accurately will influence downstream tasks drastically, such as physical parameters estimation and weak celestial source exploration. Considering that traditional locating methods are time-consuming and supervised methods require a great quantity of expensive labeled data, in this paper, we firstly investigate characteristic of interferometric fringes in simulation and real scenario respectively, and integrate almost parameter-free unsupervised clustering method and seeding filling or eraser algorithm to propose a hierarchical plug and play method to improve locating accuracy. Then, we apply our method to locate single and multiple sources' interferometric fringes in simulation data. Next, we apply our method in real data taken from Tianlai radio telescope array. Finally, we do comparison with unsupervised methods of state of the art. These results show that our method has robustness in different scenarios and can improve locating measurement accuracy effectively.","PeriodicalId":54494,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"87 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135091455","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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