利用毫米波射电天文所(Institut de Radioastronomie Millimétrique,IRAM)30 m射电望远镜在1.3–4.0 mm波段的分子谱线成图,结合70–870μm连续谱数据以及绿岸射电望远镜(Green Bank Telescope,GBT)对NH_(3)(J,K)=(1,1)和(2,2)谱...利用毫米波射电天文所(Institut de Radioastronomie Millimétrique,IRAM)30 m射电望远镜在1.3–4.0 mm波段的分子谱线成图,结合70–870μm连续谱数据以及绿岸射电望远镜(Green Bank Telescope,GBT)对NH_(3)(J,K)=(1,1)和(2,2)谱线的成图(J为总角动量量子数,而K描述角动量在分子主轴方向的分量),对G 011.0970-0.1093纤维状分子云末端的一对比邻云团进行了观测.尽管在870μm波段下它们都表现出与连续谱流量峰值成协,但在70μm波段下,它们呈现出明亮与暗弱的对照特性.对这两个云团进行对比分析发现:(1)该极早期大质量恒星形成区的气体尘埃温度高度耦合;(2)70μm明亮云团的气体尘埃温度从中心(约17 K)到包层边缘呈递减趋势,这预示着云团内部可能已经有原恒星形成;70μm暗弱云团中心较边缘更冷(约11K)更致密(约5×10^(22)cm^(-2)),且氢分子柱密度与尘埃温度存在强反相关,故外部辐射可能主导该云团加热;(3)在pc尺度上,气态C^(18)O的耗损率f_(D)(C^(18)O)与HCO^(+)的氘化率存在强正相关,且气态C^(18)O在冷且致密的DCO^(+)主导云团耗损f_(D)(C^(18)O)高达7;(4)在气体尘埃温度从10 K到20 K,氢分子柱密度从10^(22)cm^(-2)到10^(23)cm^(-2)的变化环境里,HCO^(+)、N_(2)H^(+)、HNC在更.为致密冷暗的环境氘化率增丰明显,HCN则在稍温暖且70μm明亮的环境氘化率增丰更大,而NH3氘化率在此环境中没有明显变化.这些不同分子氘化增丰的差异性可能源自其气体尘埃反应路径的差异性.展开更多
To address the issues of low accuracy and high computational complexity in traditional channelization techniques for ultra-wideband signals,this paper proposes a novel rationally oversampled channelization method to e...To address the issues of low accuracy and high computational complexity in traditional channelization techniques for ultra-wideband signals,this paper proposes a novel rationally oversampled channelization method to enhance the accuracy and efficiency of signal processing.The proposed method is evaluated by implementing and comparing critically sampled and integer oversampled channelization algorithms.A detailed analysis of the impact of different oversampling factors and filter orders on performance is provided.The validity of the proposed algorithm is verified using baseband data from pulsar J0437−4715 observed by the Parkes telescope,demonstrating its effectiveness and correctness.展开更多
Deconvolution in radio interferometry faces challenges due to incomplete sampling of the visibilities in the spatial frequency domain caused by a limited number of antenna baselines,resulting in an ill-posed inverse p...Deconvolution in radio interferometry faces challenges due to incomplete sampling of the visibilities in the spatial frequency domain caused by a limited number of antenna baselines,resulting in an ill-posed inverse problem.Reconstructing dirty images into clean ones is crucial for subsequent scientific analysis.To address these challenges,we propose a U-Net based method that extracts high-level information from the dirty image and reconstructs a clean image by effectively reducing artifacts and sidelobes.The U-Net architecture,consisting of an encoder-decoder structure and skip connections,facilitates the flow of information and preserves spatial details.Using simulated data of radio galaxies,we train our model and evaluate its performance on the testing set.Compared with the CLEAN method and the visibility and image conditioned denoising diffusion probabilistic model,our proposed model can effectively reconstruct both extended sources and faint point sources with higher values in the structural similarity index measure and the peak signal-to-noise ratio.Furthermore,we investigate the impact of noise on the model performance,demonstrating its robustness under varying noise levels.展开更多
Numerous experiments have been designed to investigate the Cosmic Dawn(CD)and Epoch of Reionization(EoR)by examining redshifted 21 cm emissions from neutral hydrogen.Detecting the global spectrum of redshifted 21 cm s...Numerous experiments have been designed to investigate the Cosmic Dawn(CD)and Epoch of Reionization(EoR)by examining redshifted 21 cm emissions from neutral hydrogen.Detecting the global spectrum of redshifted 21 cm signals is typically achieved through single-antenna experiments.However,this global 21 cm signal is deeply embedded in foreground emissions,which are about four orders of magnitude stronger.Extracting this faint signal is a significant challenge,requiring highly precise instrumental calibration.Additionally,accurately modelling receiver noise in single-antenna experiments is inherently complex.An alternative approach using a short-spacing interferometer is expected to alleviate these difficulties because the noise in different receivers is uncorrelated and averages to zero upon cross-correlation.The Short-spacing Interferometer Array for Global 21 cm Signal Detection(SIGMA)is an upcoming experiment aimed at detecting the global CD/EoR signal using this approach.We describe the SIGMA system with a focus on optimal antenna design and layout,and propose a framework to address cross-talk between antennas in future calibrations.The SIGMA system is intended to serve as a prototype to gain a better understanding of the system’s instrumental effects and to optimize its performance further.展开更多
从海量的天文观测数据中快速搜寻罕见的快速射电暴(Fast Radio Burst,FRB)事件,干扰缓解是其中一项关键而具有挑战的工作.射频干扰(Radio Frequency Interference,RFI)会淹没真实的天文事件,还会导致搜寻管线输出大量的假阳性候选体.由...从海量的天文观测数据中快速搜寻罕见的快速射电暴(Fast Radio Burst,FRB)事件,干扰缓解是其中一项关键而具有挑战的工作.射频干扰(Radio Frequency Interference,RFI)会淹没真实的天文事件,还会导致搜寻管线输出大量的假阳性候选体.由于干扰来源及其种类的复杂性,目前并没有一种通用的方法可以解决这个问题.为了降低干扰对FRB观测搜寻的影响,分析和研究了南山26m射电望远镜L波段观测数据中的干扰情况,针对主要的窄带干扰和宽带干扰建立了3层次的干扰缓解处理流程,从而有效缓解了观测数据的干扰污染情况.将该流程嵌入到FRB色散动态谱搜寻(Dispersed Dynamic Spectra Search,DDSS)管线中,实验结果表明,搜寻管线的检测率和检测精度得到了进一步的提高.该方法为FRB观测数据干扰缓解处理提供了有价值的参考.展开更多
无线电频率占用度是表征无线电频谱真实占用状况的主要指标。针对目前国家规范测量无线电频率占用度以及频率占用度与无线信道状态关联研究存在的问题,建立了无线电信号发射与频谱接收系统,研究了无线电频率占用度测量方法与信道噪声模...无线电频率占用度是表征无线电频谱真实占用状况的主要指标。针对目前国家规范测量无线电频率占用度以及频率占用度与无线信道状态关联研究存在的问题,建立了无线电信号发射与频谱接收系统,研究了无线电频率占用度测量方法与信道噪声模型的关系。实验结果表明,如果信道是高斯噪声信道,可采用国标法进行频率占用度测量;如果信道是非高斯噪声信道,采用5西格玛原则统计频率占用度更好。采用机器学习方法研究了无线信道占用状况,结果表明,信噪比(Signal to Noise Ratio,SNR)大于15 dB时,基于信号频谱分类模型的5类无线电信号的分类准确率可达到99%以上;在低SNR和非高斯噪声信道下如何进一步提高无线电信号的分类准确率是一个挑战。展开更多
Accurate estimation of Zenith Tropospheric Delay(ZTD)is essential for mitigating atmospheric effects in radio astronomical observations and improving the retrieval of precipitable water vapor(PWV).In this study,we fir...Accurate estimation of Zenith Tropospheric Delay(ZTD)is essential for mitigating atmospheric effects in radio astronomical observations and improving the retrieval of precipitable water vapor(PWV).In this study,we first analyze the periodic characteristics of ZTD at the NanShan Radio Telescope site using Fourier transform,revealing its dominant seasonal variations,and then investigate the correlation between ZTD and local meteorological parameters,to better understand atmospheric influences on tropospheric delay.Based on these analyses,we propose a hybrid deep learning Gated Recurrent Units-Long Short-Term Memory model,incorporating meteorological parameters as external inputs to enhance ZTD forecasting accuracy.Experimental results demonstrate that the proposed approach achieves a Root Mean Squared Error of 7.97 mm and a correlation coefficient R of 96%,significantly outperforming traditional empirical models and standalone deep learning architectures.These findings indicate that the model effectively captures both short-term dynamics and long-term dependencies in ZTD variations.The improved ZTD predictions not only contribute to reducing atmospheric errors in radio astronomical observations but also provide a more reliable basis for PWV retrieval and forecasting.This study highlights the potential of deep learning in tropospheric delay modeling,offering advancements in both atmospheric science and geodetic applications.展开更多
我国正在进行大口径单天线和阵列射电望远镜的建设和预研工作。为保障射电望远镜前期建设工作的开展,首先需要找到满足电磁环境要求的台址,本文使用搬移式电磁环境监测装备在广东省清远市阳山县杜步镇、水口镇等预选台址开展了电磁环境...我国正在进行大口径单天线和阵列射电望远镜的建设和预研工作。为保障射电望远镜前期建设工作的开展,首先需要找到满足电磁环境要求的台址,本文使用搬移式电磁环境监测装备在广东省清远市阳山县杜步镇、水口镇等预选台址开展了电磁环境监测,并对广州市白云区帽峰山开展对比测试,采用一种干扰阈值判断方法对电磁环境监测数据进行了分析。分析结果显示,位于清远市阳山县杜步镇附近的洼地射频干扰(radio frequency interference,RFI)数量少且强度弱,该洼地远离城市中心,经济活动少,周围群山环抱,具有良好的电磁隔离性,适合大口径单天线和阵列射电望远镜的建设。本文的数据分析结果可为大口径射电望远镜的选址提供依据。展开更多
This study presents results on detecting neutral atomic hydrogen(H I)21 cm absorption in the spectrum of PKS PKS1413+13 at redshift z=0.24670041.The observation was conducted by FAST,with a spectral resolution of10 Hz...This study presents results on detecting neutral atomic hydrogen(H I)21 cm absorption in the spectrum of PKS PKS1413+13 at redshift z=0.24670041.The observation was conducted by FAST,with a spectral resolution of10 Hz,using 10 minutes of observing time.The global spectral profile is examined by modeling the absorption line using a single Gaussian function with a resolution of 10 kHz within a 2 MHz bandwidth.The goal is to determine the rate of the latest cosmic acceleration by directly measuring the redshift evolution of the H I 21 cm absorption line with Hubble flow toward a common background quasar over a decade or longer time span.This will serve as a detectable signal generated by the accelerated expansion of the Universe at redshift z<1,referred to as redshift drift z(5)or the SL effect.The measured H I gas column density in this DLA system is approximately equivalent to the initial observation value,considering uncertainties of the spin temperature of a spiral host galaxy.The high signal-to-noise ratio of 57,obtained at a 10 kHz resolution,strongly supports the feasibility of using the H I 21 cm absorption line in DLA systems to accurately measure the redshift drift rate at a precision level of around 10~(-10)per decade.展开更多
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.The array,consist...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.The 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 semi-sphere.The FRB digital backend enables the formation of 96 digital beams,effectively covering an area of approximately 40 square degrees with the 3 dB beam.Our pipeline demonstrates the capability to conduct an automatic search of FRBs,detecting at quasi-realtime and classifying FRB candidates automatically.The 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+28.We report the first discovery of an FRB by our array,designated as FRB 20220414A.We also investigate the optimal arrangement for the digitally formed beams to achieve maximum detection rate by numerical simulation.展开更多
Fast radio bursts(FRBs)are short-duration radio transients with mysterious origins.Since their uncertainty,there are very few FRBs observed by different instruments simultaneously.This study presents a detailed analys...Fast radio bursts(FRBs)are short-duration radio transients with mysterious origins.Since their uncertainty,there are very few FRBs observed by different instruments simultaneously.This study presents a detailed analysis of a burst from FRB 20190520B observed by FAST and Parkes at the same time.The spectrum of this individual burst ended at the upper limit of the FAST frequency band and was simultaneously detected by the Parkes telescope in the 1.5–1.8GHz range.By employing spectral energy distribution(SED)and spectral sharpness methods,we confirmed the presence of narrow-band radiation in FRB 20190520B,which is crucial for understanding its radiation mechanisms.Our findings support the narrow-band characteristics that most repeaters exhibit.This work also highlights the necessity of continued multiband observations to explore its periodicity and frequency-dependent properties,contributing to an in-depth understanding of FRB phenomena.展开更多
Radio astronomy necessitates radio frequency bands that are both stable and free from interference at observatory locations.To comprehensively evaluate the radio environment at radio observatories,we employ Monte Carl...Radio astronomy necessitates radio frequency bands that are both stable and free from interference at observatory locations.To comprehensively evaluate the radio environment at radio observatories,we employ Monte Carlo methods to assess the quality of observational data and predict potential interference.With an extensive dataset,we used an algorithm to find the interference threshold within the L-band,automatically identifying disruptive signals.Monte Carlo simulations were conducted to estimate whether these interference signals surpass a predetermined threshold of the total observation period,facilitating a detailed analysis of the interference profile.A Monte Carlo analysis was used on 83 hours of continuous monitoring data using a wireless environment testing system,to forecast the proportion of time during which interference signals would surpass established harmful thresholds.Our findings indicate that,within the L-band spectrum at Fenghuang Hill,Kunming City,Yunnan Province,the incidence of interference within the frequency ranges of 1330–1440 MHz,1610–1613 MHz,and 1660–1670 MHz is acceptably low,with respective confidence levels of 96.9%,97.4%,and 97.4%that the proportion of time these interference signals occupy does not exceed 5%of the total observational time,as stipulated by the International Telecommunication Union.Conversely,the confidence level for the 1718–1722 MHz band not exceeding 5%of the total observational time is significantly lower at 88.5%.This study offers a valuable tool for assessing the radio environment in radio astronomy research and provides a foundational basis for the scientific management and safeguarding of radio frequency bands.展开更多
About this issue:Radar astronomy is a science that utilizes radar electromagnetic waves to study celestial bodies within and beyond the solar system,focusing mainly on planets,satellites and small bodies such as the M...About this issue:Radar astronomy is a science that utilizes radar electromagnetic waves to study celestial bodies within and beyond the solar system,focusing mainly on planets,satellites and small bodies such as the Moon,Mars,Venus and Saturn.Through radar electromagnetic wave detection,we are able to gain an in-depth understanding of these celestial bodies'internal structures,composition,distribution of water resources,magnetic fields,atmospheres,and other physical properties.This is of great significance for human beings to find a habitable environment in the solar system.At present,the observation methods of radar astronomy mainly rely on ground-based radio telescopes that actively emit electromagnetic waves.展开更多
基金supported by the National Key R&D Program of China Nos.2021YFC2203502 and 2022YFF0711502the National Natural Science Foundation of China(NSFC)(12173077)+5 种基金the Chinese Academy of Sciences(CAS)“Light of West China”Program(No.xbzg-zdsys-202410)the Tianshan Talent Project of Xinjiang Uygur Autonomous Region(2022TSYCCX0095 and 2023TSYCCX0112)the Scientific Instrument Developing Project of the Chinese Academy of Sciences,grant No.PTYQ2022YZZD01China 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To address the issues of low accuracy and high computational complexity in traditional channelization techniques for ultra-wideband signals,this paper proposes a novel rationally oversampled channelization method to enhance the accuracy and efficiency of signal processing.The proposed method is evaluated by implementing and comparing critically sampled and integer oversampled channelization algorithms.A detailed analysis of the impact of different oversampling factors and filter orders on performance is provided.The validity of the proposed algorithm is verified using baseband data from pulsar J0437−4715 observed by the Parkes telescope,demonstrating its effectiveness and correctness.
基金supported by the National SKA Program of China(2020SKA0110300,2020SKA0110201)the National Natural Science Foundation of China(NSFC,grant Nos.12433012 and 12373097)+1 种基金the Guangdong Province Project of the Basic and Applied Basic Research Foundation(2024A1515011503)the Guangzhou Science and Technology Funds(2023A03J0016).
文摘Deconvolution in radio interferometry faces challenges due to incomplete sampling of the visibilities in the spatial frequency domain caused by a limited number of antenna baselines,resulting in an ill-posed inverse problem.Reconstructing dirty images into clean ones is crucial for subsequent scientific analysis.To address these challenges,we propose a U-Net based method that extracts high-level information from the dirty image and reconstructs a clean image by effectively reducing artifacts and sidelobes.The U-Net architecture,consisting of an encoder-decoder structure and skip connections,facilitates the flow of information and preserves spatial details.Using simulated data of radio galaxies,we train our model and evaluate its performance on the testing set.Compared with the CLEAN method and the visibility and image conditioned denoising diffusion probabilistic model,our proposed model can effectively reconstruct both extended sources and faint point sources with higher values in the structural similarity index measure and the peak signal-to-noise ratio.Furthermore,we investigate the impact of noise on the model performance,demonstrating its robustness under varying noise levels.
基金supported by the National SKA Program of China(No.2020SKA0110200 and No.2020SKA0110100)Y.Y.acknowledges the support of the Key Program of National Natural Science Foundation of China(12433012)。
文摘Numerous experiments have been designed to investigate the Cosmic Dawn(CD)and Epoch of Reionization(EoR)by examining redshifted 21 cm emissions from neutral hydrogen.Detecting the global spectrum of redshifted 21 cm signals is typically achieved through single-antenna experiments.However,this global 21 cm signal is deeply embedded in foreground emissions,which are about four orders of magnitude stronger.Extracting this faint signal is a significant challenge,requiring highly precise instrumental calibration.Additionally,accurately modelling receiver noise in single-antenna experiments is inherently complex.An alternative approach using a short-spacing interferometer is expected to alleviate these difficulties because the noise in different receivers is uncorrelated and averages to zero upon cross-correlation.The Short-spacing Interferometer Array for Global 21 cm Signal Detection(SIGMA)is an upcoming experiment aimed at detecting the global CD/EoR signal using this approach.We describe the SIGMA system with a focus on optimal antenna design and layout,and propose a framework to address cross-talk between antennas in future calibrations.The SIGMA system is intended to serve as a prototype to gain a better understanding of the system’s instrumental effects and to optimize its performance further.
文摘从海量的天文观测数据中快速搜寻罕见的快速射电暴(Fast Radio Burst,FRB)事件,干扰缓解是其中一项关键而具有挑战的工作.射频干扰(Radio Frequency Interference,RFI)会淹没真实的天文事件,还会导致搜寻管线输出大量的假阳性候选体.由于干扰来源及其种类的复杂性,目前并没有一种通用的方法可以解决这个问题.为了降低干扰对FRB观测搜寻的影响,分析和研究了南山26m射电望远镜L波段观测数据中的干扰情况,针对主要的窄带干扰和宽带干扰建立了3层次的干扰缓解处理流程,从而有效缓解了观测数据的干扰污染情况.将该流程嵌入到FRB色散动态谱搜寻(Dispersed Dynamic Spectra Search,DDSS)管线中,实验结果表明,搜寻管线的检测率和检测精度得到了进一步的提高.该方法为FRB观测数据干扰缓解处理提供了有价值的参考.
文摘无线电频率占用度是表征无线电频谱真实占用状况的主要指标。针对目前国家规范测量无线电频率占用度以及频率占用度与无线信道状态关联研究存在的问题,建立了无线电信号发射与频谱接收系统,研究了无线电频率占用度测量方法与信道噪声模型的关系。实验结果表明,如果信道是高斯噪声信道,可采用国标法进行频率占用度测量;如果信道是非高斯噪声信道,采用5西格玛原则统计频率占用度更好。采用机器学习方法研究了无线信道占用状况,结果表明,信噪比(Signal to Noise Ratio,SNR)大于15 dB时,基于信号频谱分类模型的5类无线电信号的分类准确率可达到99%以上;在低SNR和非高斯噪声信道下如何进一步提高无线电信号的分类准确率是一个挑战。
基金funded by the CAS“Light of West China”Program(grant Nos.2021-XBQNXZ-030 and 2021-XBQNXZ-005)the Xinjiang Key Laboratory of Radio Astrophysics(grant No.2023D04064)the National Key R&D Program of China(grant No.2024YFA1611503)。
文摘Accurate estimation of Zenith Tropospheric Delay(ZTD)is essential for mitigating atmospheric effects in radio astronomical observations and improving the retrieval of precipitable water vapor(PWV).In this study,we first analyze the periodic characteristics of ZTD at the NanShan Radio Telescope site using Fourier transform,revealing its dominant seasonal variations,and then investigate the correlation between ZTD and local meteorological parameters,to better understand atmospheric influences on tropospheric delay.Based on these analyses,we propose a hybrid deep learning Gated Recurrent Units-Long Short-Term Memory model,incorporating meteorological parameters as external inputs to enhance ZTD forecasting accuracy.Experimental results demonstrate that the proposed approach achieves a Root Mean Squared Error of 7.97 mm and a correlation coefficient R of 96%,significantly outperforming traditional empirical models and standalone deep learning architectures.These findings indicate that the model effectively captures both short-term dynamics and long-term dependencies in ZTD variations.The improved ZTD predictions not only contribute to reducing atmospheric errors in radio astronomical observations but also provide a more reliable basis for PWV retrieval and forecasting.This study highlights the potential of deep learning in tropospheric delay modeling,offering advancements in both atmospheric science and geodetic applications.
文摘我国正在进行大口径单天线和阵列射电望远镜的建设和预研工作。为保障射电望远镜前期建设工作的开展,首先需要找到满足电磁环境要求的台址,本文使用搬移式电磁环境监测装备在广东省清远市阳山县杜步镇、水口镇等预选台址开展了电磁环境监测,并对广州市白云区帽峰山开展对比测试,采用一种干扰阈值判断方法对电磁环境监测数据进行了分析。分析结果显示,位于清远市阳山县杜步镇附近的洼地射频干扰(radio frequency interference,RFI)数量少且强度弱,该洼地远离城市中心,经济活动少,周围群山环抱,具有良好的电磁隔离性,适合大口径单天线和阵列射电望远镜的建设。本文的数据分析结果可为大口径射电望远镜的选址提供依据。
基金supported by the National SKA Program of China(2022SKA0110202)the National Natural Science Foundation of China(grants No.11929301)。
文摘This study presents results on detecting neutral atomic hydrogen(H I)21 cm absorption in the spectrum of PKS PKS1413+13 at redshift z=0.24670041.The observation was conducted by FAST,with a spectral resolution of10 Hz,using 10 minutes of observing time.The global spectral profile is examined by modeling the absorption line using a single Gaussian function with a resolution of 10 kHz within a 2 MHz bandwidth.The goal is to determine the rate of the latest cosmic acceleration by directly measuring the redshift evolution of the H I 21 cm absorption line with Hubble flow toward a common background quasar over a decade or longer time span.This will serve as a detectable signal generated by the accelerated expansion of the Universe at redshift z<1,referred to as redshift drift z(5)or the SL effect.The measured H I gas column density in this DLA system is approximately equivalent to the initial observation value,considering uncertainties of the spin temperature of a spiral host galaxy.The high signal-to-noise ratio of 57,obtained at a 10 kHz resolution,strongly supports the feasibility of using the H I 21 cm absorption line in DLA systems to accurately measure the redshift drift rate at a precision level of around 10~(-10)per decade.
基金support of the National SKA program of China(Nos.2022SKA0110100 and 2022SKA0110101)the National Natural Science Foundation of China(NSFC,Grant Nos.1236114814,12203061,12273070,and 12303004)。
文摘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.The 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 semi-sphere.The FRB digital backend enables the formation of 96 digital beams,effectively covering an area of approximately 40 square degrees with the 3 dB beam.Our pipeline demonstrates the capability to conduct an automatic search of FRBs,detecting at quasi-realtime and classifying FRB candidates automatically.The 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+28.We report the first discovery of an FRB by our array,designated as FRB 20220414A.We also investigate the optimal arrangement for the digitally formed beams to achieve maximum detection rate by numerical simulation.
基金supported by the National Natural Science Foundation of China(Grant Nos.11988101,12203069,12041302,and 12203045)the National SKA Program of China(Grant No.2022SKA0130100)+8 种基金the Office of the Leading Group for Cyberspace Affairs,CAS(Grant No.CAS-WX2023PY0102)the CAS Youth Interdisciplinary Team and the Foundation of Guizhou Provincial Education Department(Grant No.KY(2023)059)support from the National Natural Science Foundation of China(Grant Nos.11988101 and 12041303)the CAS Youth Interdisciplinary Team,the Youth Innovation Promotion Association CAS(Grant No.2021055)the Cultivation Project for FAST Scientific Payoff and Research Achievement of CAMS-CASsupported by the National Natural Science Foundation of China(Grant No.12203045)the Leading Innovation and Entrepreneurship Team of Zhejiang Province of China(Grant No.2023R01008)the Key R&D Program of Zhejiang(Grant No.2024SSYS0012)supported by the China Scholarship Council(Grant No.202304910441)。
文摘Fast radio bursts(FRBs)are short-duration radio transients with mysterious origins.Since their uncertainty,there are very few FRBs observed by different instruments simultaneously.This study presents a detailed analysis of a burst from FRB 20190520B observed by FAST and Parkes at the same time.The spectrum of this individual burst ended at the upper limit of the FAST frequency band and was simultaneously detected by the Parkes telescope in the 1.5–1.8GHz range.By employing spectral energy distribution(SED)and spectral sharpness methods,we confirmed the presence of narrow-band radiation in FRB 20190520B,which is crucial for understanding its radiation mechanisms.Our findings support the narrow-band characteristics that most repeaters exhibit.This work also highlights the necessity of continued multiband observations to explore its periodicity and frequency-dependent properties,contributing to an in-depth understanding of FRB phenomena.
基金Construction of the Science and Technology Innovation Center for South Asia and Southeast Asia-Yunnan Province International Joint Innovation Platform: “Yunnan Province China-Malaysia HF-VHF Advanced Radio Astronomy Technology International Joint Laboratory” (202303AP140003)The National Natural Science Foundation of China Astronomical Joint Fund Cultivation Project (U203 1133)+4 种基金The SKA Special Project of the Ministry of Science and Technology (2020SKA0110202)The International Partnership Program of Bureau of International Cooperation, Chinese Academy of Sciences: 'Belt and Road' cooperation (114A11KYSB 20200001)The Kunming International (International) Cooperation Base project: “Yunnan Astronomical Observatory-University of Malaya Advanced Radio Astronomy Technology, Chinese Academy of Sciences” (GHJD2021022)The key special project of the Ministry of Science and Technology under the “Space Remote Sensing and Radio Astronomical Observation” of the Ministry of Science and Technology (2022YFE0140000)The High-precision calibration method of the SKA special low-frequency radio interference array of the Ministry of Science and Technology (2020SKA011 0300)
文摘Radio astronomy necessitates radio frequency bands that are both stable and free from interference at observatory locations.To comprehensively evaluate the radio environment at radio observatories,we employ Monte Carlo methods to assess the quality of observational data and predict potential interference.With an extensive dataset,we used an algorithm to find the interference threshold within the L-band,automatically identifying disruptive signals.Monte Carlo simulations were conducted to estimate whether these interference signals surpass a predetermined threshold of the total observation period,facilitating a detailed analysis of the interference profile.A Monte Carlo analysis was used on 83 hours of continuous monitoring data using a wireless environment testing system,to forecast the proportion of time during which interference signals would surpass established harmful thresholds.Our findings indicate that,within the L-band spectrum at Fenghuang Hill,Kunming City,Yunnan Province,the incidence of interference within the frequency ranges of 1330–1440 MHz,1610–1613 MHz,and 1660–1670 MHz is acceptably low,with respective confidence levels of 96.9%,97.4%,and 97.4%that the proportion of time these interference signals occupy does not exceed 5%of the total observational time,as stipulated by the International Telecommunication Union.Conversely,the confidence level for the 1718–1722 MHz band not exceeding 5%of the total observational time is significantly lower at 88.5%.This study offers a valuable tool for assessing the radio environment in radio astronomy research and provides a foundational basis for the scientific management and safeguarding of radio frequency bands.
文摘About this issue:Radar astronomy is a science that utilizes radar electromagnetic waves to study celestial bodies within and beyond the solar system,focusing mainly on planets,satellites and small bodies such as the Moon,Mars,Venus and Saturn.Through radar electromagnetic wave detection,we are able to gain an in-depth understanding of these celestial bodies'internal structures,composition,distribution of water resources,magnetic fields,atmospheres,and other physical properties.This is of great significance for human beings to find a habitable environment in the solar system.At present,the observation methods of radar astronomy mainly rely on ground-based radio telescopes that actively emit electromagnetic waves.
