As artificial intelligence(AI)technology has continued to develop,its efficient data processing and pattern recognition capabilities have significantly improved the precision and speed of decision-making processes,and...As artificial intelligence(AI)technology has continued to develop,its efficient data processing and pattern recognition capabilities have significantly improved the precision and speed of decision-making processes,and it has been widely applied across various fields.In the field of astronomy,AI techniques have demonstrated unique advantages,particularly in the identification of pulsars and their candidates.AI is able to address the challenges of pulsar celestial body identification and classification because of its accuracy and efficiency.This paper systematically surveys commonly used AI models for pulsar candidate identification,analyzing and discussing the typical applications of machine learning,artificial neural networks,convolutional neural networks,and generative adversarial networks in candidate identification.Furthermore,it explores how th.e introduction of AI techniques not only enhances the efficiency and accuracy of pulsar identification but also provides new perspectives and tools for pulsar survey data processing,thus playing a significant role in advancing pulsar research and the field of astronomy.展开更多
2009年11月,云南天文台射电天文研究团组采用40 m射电望远镜以及基于DBBC(Digital Base Band Conveter)和Mark 5B的VLBI记录系统对PSR J0835-4510和PSRJ0332+5434进行了观测。观测选用S波段右旋圆极化信号,起始频率为2 206.99 MHz,总带...2009年11月,云南天文台射电天文研究团组采用40 m射电望远镜以及基于DBBC(Digital Base Band Conveter)和Mark 5B的VLBI记录系统对PSR J0835-4510和PSRJ0332+5434进行了观测。观测选用S波段右旋圆极化信号,起始频率为2 206.99 MHz,总带宽为32 MHz。对数据进行相干消色散和平均后,得到PSR J0332+5434的单脉冲图像和两颗脉冲星的平均脉冲轮廓。由平均轮廓的展宽随时间的变化关系,对脉冲星的视周期作了一定修正后,得到信噪比更高的平均轮廓图。最后对轮廓的信噪比随时间的变化作了初步分析,由此可了解整个系统在观测时的稳定性。展开更多
The FAST radio telescope has significantly better sensitivity than any other current radio telescope.Consequently,FAST has discovered over a thousand new pulsars in sky regions already searched for 50 yr.The Galactic ...The FAST radio telescope has significantly better sensitivity than any other current radio telescope.Consequently,FAST has discovered over a thousand new pulsars in sky regions already searched for 50 yr.The Galactic Plane Pulsar Snapshot(GPPS)survey found three-quarters of these new pulsars.The article by Han et al.(2025)details the latest batch of 473 discoveries,bringing the total to 751.展开更多
A group of Chinese astronomers detected a weird pulsar that keeps emitting radio beams in long,regular pauses.After years of follow-up observations and careful data analyses,they finally revealed this exotic pulsar in...A group of Chinese astronomers detected a weird pulsar that keeps emitting radio beams in long,regular pauses.After years of follow-up observations and careful data analyses,they finally revealed this exotic pulsar in Science on May 23 as a rare case:it turns out to be eclipsed by a companion,very likely a helium star,with a mass similar to the Sun and in an orbit smaller than the solar radius.展开更多
We present a comprehensive analysis of AstroSat/LAXPC data of the second spin-up and second spin-down phases of the persistent X-ray pulsar 4U 1626-67.Flares followed by a broad dip are detected in the spin-up observa...We present a comprehensive analysis of AstroSat/LAXPC data of the second spin-up and second spin-down phases of the persistent X-ray pulsar 4U 1626-67.Flares followed by a broad dip are detected in the spin-up observations.The pulse profiles changed from a shoulder-like structure to a broad sinusoidal shape as the source underwent a torque reversal from spin-up to spin-down.Energy-resolved pulse profiles in lower energies showed a double-horned profile in the spin-up state and a flat top with multiple peaks in the spin-down state.Regardless of the torque state,the pulse profiles exhibit a broad single-peaked shape at higher energies.The observation in the spin-down era is characterized by the presence of a prominent QPO at 46.5±1.0 mHz frequency.The QPO rms and center frequency show a correlation with energy.Spin-up and spin-down states show a difference in the shape of the power density spectrum.After the torque reversal,a gradual flux drop and the hardening of the spectra were observed.The difference in the shape of the pulse profiles and the presence and absence of QPOs can be explained by the change in accretion flow geometry of the pulsar,from pencil-beam to fan-beam,between spin-down and spin-up states.展开更多
Sterile neutrinos can influence the evolution of the Universe,and thus cosmological observations can be used to detect them.Future gravitational-wave(GW)observations can precisely measure absolute cosmological distanc...Sterile neutrinos can influence the evolution of the Universe,and thus cosmological observations can be used to detect them.Future gravitational-wave(GW)observations can precisely measure absolute cosmological distances,helping to break parameter degeneracies generated by traditional cosmological observations.This advancement can lead to much tighter constraints on sterile neutrino parameters.This work provides a preliminary forecast for detecting sterile neutrinos using third-generation GW detectors in combination with future shortγ-ray burst observations from a THESEUS-like telescope,an approach not previously explored in the literature.Both massless and massive sterile neutrinos are considered within theΛCDM cosmology.We find that using GW data can greatly enhance the detection capability for massless sterile neutrinos,reaching 3σlevel.For massive sterile neutrinos,GW data can also greatly assist in improving the parameter constraints,but it seems that effective detection is still not feasible.展开更多
Pulsar candidate identification is an indispensable task in pulsar science.Based on the characteristics of imbalanced and diverse pulsar data sets,and the lack of a unified processing framework,we first used dimension...Pulsar candidate identification is an indispensable task in pulsar science.Based on the characteristics of imbalanced and diverse pulsar data sets,and the lack of a unified processing framework,we first used dimensionality reduction and visualization to analyze potential deficiencies caused by the incompleteness of current data set extraction methods.We found that the limited use of non-pulsar data may lead to bias in the result,which may limit the generalization ability.Based on the dimensionality reduction results,we propose a Grid Group Uniform Sampling(GGUS) method.This data preprocessing method improves the performance of Random Forest,Support Vector Machine,Convolutional Neural Network,and Res Net50 models on Lyon’s features,diagnostic plots,and perioddispersion measure (period-DM) plots in the HTRU1 data set.The average recall increased by approximately0.5%,precision by nearly 2%,and F_(1) score by around 1.2%for all models and in all data sets.In the period-DM plots testing,the high-performance Res Net50 algorithm achieved over 98%F_(1) using random sampling.GGUS demonstrated further improvements in this test,enhancing the average F_(1) score,precision,and recall by approximately 0.07%,0.1%,and 0.03%,respectively.展开更多
This paper yields a new exact solution for dense stellar objects by employing the Einstein-Maxwell system of differential equations.The established model comprises three interior layers with distinguishable equations ...This paper yields a new exact solution for dense stellar objects by employing the Einstein-Maxwell system of differential equations.The established model comprises three interior layers with distinguishable equations of state(EoSs):the polytropic EoS at the core layer,the quadratic EoS at the intermediate layer and the modified Van der Waals EoS at the envelope layer.The physical features indicate that the matter variables,metric functions and other physical conditions are viable with dense astrophysical objects.Excitingly,this model is an extension solution of the two-layered model generated by Sunzu and Lighuda.The layers are matched gently across the junctions with the care of the Reissner-Nordström exterior spacetime.Utilizing our model,star masses and radii compatible with observations and satisfactorily known objects are generated.The findings from this paper may be useful to describes purported strange stars such as SAX J1808.4-3658 and binary stars such as Vela X-1.展开更多
基金supported by the National Key R&D Program of China(2021YFC2203502 and 2022YFF0711502)the National Natural Science Foundation of China(NSFC)(12173077)+4 种基金the Tianshan Talent Project of Xinjiang Uygur Autonomous Region(2022TSYCCX0095 and 2023TSYCCX0112)the Scientific Instrument Developing Project of the Chinese Academy of Sciences(PTYQ2022YZZD01)China National Astronomical Data Center(NADC)the Operation,Maintenance and Upgrading Fund for Astronomical Telescopes and Facility Instruments,budgeted from the Ministry of Finance of China(MOF)and administrated by the Chinese Academy of Sciences(CAS)Natural Science Foundation of Xinjiang Uygur Autonomous Region(2022D01A360)。
文摘As artificial intelligence(AI)technology has continued to develop,its efficient data processing and pattern recognition capabilities have significantly improved the precision and speed of decision-making processes,and it has been widely applied across various fields.In the field of astronomy,AI techniques have demonstrated unique advantages,particularly in the identification of pulsars and their candidates.AI is able to address the challenges of pulsar celestial body identification and classification because of its accuracy and efficiency.This paper systematically surveys commonly used AI models for pulsar candidate identification,analyzing and discussing the typical applications of machine learning,artificial neural networks,convolutional neural networks,and generative adversarial networks in candidate identification.Furthermore,it explores how th.e introduction of AI techniques not only enhances the efficiency and accuracy of pulsar identification but also provides new perspectives and tools for pulsar survey data processing,thus playing a significant role in advancing pulsar research and the field of astronomy.
文摘The FAST radio telescope has significantly better sensitivity than any other current radio telescope.Consequently,FAST has discovered over a thousand new pulsars in sky regions already searched for 50 yr.The Galactic Plane Pulsar Snapshot(GPPS)survey found three-quarters of these new pulsars.The article by Han et al.(2025)details the latest batch of 473 discoveries,bringing the total to 751.
文摘A group of Chinese astronomers detected a weird pulsar that keeps emitting radio beams in long,regular pauses.After years of follow-up observations and careful data analyses,they finally revealed this exotic pulsar in Science on May 23 as a rare case:it turns out to be eclipsed by a companion,very likely a helium star,with a mass similar to the Sun and in an orbit smaller than the solar radius.
基金financial support from ISRO(Sanction Order:No.DS_2B-13013(2)/3/2021-Sec.2)。
文摘We present a comprehensive analysis of AstroSat/LAXPC data of the second spin-up and second spin-down phases of the persistent X-ray pulsar 4U 1626-67.Flares followed by a broad dip are detected in the spin-up observations.The pulse profiles changed from a shoulder-like structure to a broad sinusoidal shape as the source underwent a torque reversal from spin-up to spin-down.Energy-resolved pulse profiles in lower energies showed a double-horned profile in the spin-up state and a flat top with multiple peaks in the spin-down state.Regardless of the torque state,the pulse profiles exhibit a broad single-peaked shape at higher energies.The observation in the spin-down era is characterized by the presence of a prominent QPO at 46.5±1.0 mHz frequency.The QPO rms and center frequency show a correlation with energy.Spin-up and spin-down states show a difference in the shape of the power density spectrum.After the torque reversal,a gradual flux drop and the hardening of the spectra were observed.The difference in the shape of the pulse profiles and the presence and absence of QPOs can be explained by the change in accretion flow geometry of the pulsar,from pencil-beam to fan-beam,between spin-down and spin-up states.
基金supported by the National Natural Science Foundation of China under Grant Nos.12305069,11947022,12473001,11975072,11875102,and 11835009the National SKA Program of China under Grants Nos.2022SKA0110200 and 2022SKA0110203+1 种基金the Program of the Education Department of Liaoning Province under Grant No.JYTMS20231695the National 111 Project under Grant No.B16009。
文摘Sterile neutrinos can influence the evolution of the Universe,and thus cosmological observations can be used to detect them.Future gravitational-wave(GW)observations can precisely measure absolute cosmological distances,helping to break parameter degeneracies generated by traditional cosmological observations.This advancement can lead to much tighter constraints on sterile neutrino parameters.This work provides a preliminary forecast for detecting sterile neutrinos using third-generation GW detectors in combination with future shortγ-ray burst observations from a THESEUS-like telescope,an approach not previously explored in the literature.Both massless and massive sterile neutrinos are considered within theΛCDM cosmology.We find that using GW data can greatly enhance the detection capability for massless sterile neutrinos,reaching 3σlevel.For massive sterile neutrinos,GW data can also greatly assist in improving the parameter constraints,but it seems that effective detection is still not feasible.
基金supported by the National Key Research and Development Program of China under grant No.2018YFA0404603supported by the Operation,Maintenance and Upgrading Fund for Astronomical Telescopes and Facility Instruments,budgeted from the Ministry of Finance of China (MOF) and administered by the Chinese Academy of Sciences (CAS)。
文摘Pulsar candidate identification is an indispensable task in pulsar science.Based on the characteristics of imbalanced and diverse pulsar data sets,and the lack of a unified processing framework,we first used dimensionality reduction and visualization to analyze potential deficiencies caused by the incompleteness of current data set extraction methods.We found that the limited use of non-pulsar data may lead to bias in the result,which may limit the generalization ability.Based on the dimensionality reduction results,we propose a Grid Group Uniform Sampling(GGUS) method.This data preprocessing method improves the performance of Random Forest,Support Vector Machine,Convolutional Neural Network,and Res Net50 models on Lyon’s features,diagnostic plots,and perioddispersion measure (period-DM) plots in the HTRU1 data set.The average recall increased by approximately0.5%,precision by nearly 2%,and F_(1) score by around 1.2%for all models and in all data sets.In the period-DM plots testing,the high-performance Res Net50 algorithm achieved over 98%F_(1) using random sampling.GGUS demonstrated further improvements in this test,enhancing the average F_(1) score,precision,and recall by approximately 0.07%,0.1%,and 0.03%,respectively.
文摘This paper yields a new exact solution for dense stellar objects by employing the Einstein-Maxwell system of differential equations.The established model comprises three interior layers with distinguishable equations of state(EoSs):the polytropic EoS at the core layer,the quadratic EoS at the intermediate layer and the modified Van der Waals EoS at the envelope layer.The physical features indicate that the matter variables,metric functions and other physical conditions are viable with dense astrophysical objects.Excitingly,this model is an extension solution of the two-layered model generated by Sunzu and Lighuda.The layers are matched gently across the junctions with the care of the Reissner-Nordström exterior spacetime.Utilizing our model,star masses and radii compatible with observations and satisfactorily known objects are generated.The findings from this paper may be useful to describes purported strange stars such as SAX J1808.4-3658 and binary stars such as Vela X-1.
