We use the Richardson-Lucy deconvolution algorithm to extract one-dimensional(1 D) spectra from Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST) spectrum images. Compared with other deconvolution algo...We use the Richardson-Lucy deconvolution algorithm to extract one-dimensional(1 D) spectra from Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST) spectrum images. Compared with other deconvolution algorithms, this algorithm is much faster. The application on a real LAMOST image illustrates that the 1 D spectrum resulting from this method has a higher signal-to-noise ratio and resolution than those extracted by the LAMOST pipeline. Furthermore, our algorithm can effectively suppress the ringings that are often present in the 1 D resulting spectra generated by other deconvolution methods.展开更多
The dynamic spectral observation at decametric wavelength is important to study solar radio physics and space weather.However,the observing system is difficult to observe with high sensitivity at this band due to the ...The dynamic spectral observation at decametric wavelength is important to study solar radio physics and space weather.However,the observing system is difficult to observe with high sensitivity at this band due to the fact that the system temperature is dominated by the sky background noise and the antenna is difficult to design with high gain.An effective solution to improve the sensitivity is constructing an antenna array based on the beamforming method.Accordingly,we develop a decametric solar radio spectrometer system based on a 4-element beamforming array.The system consists of four antennas,an 8-channel analog receiver and a digital receiver.We use the true time delay to implement the beamformer and the classical FFT method to perform spectrum analysis in the digital receiver.Operating at a frequency range of 25–65 MHz with dual-circular polarizations,the system provides high resolution dynamic spectrum with spectral resolution of~12 kHz and temporal resolution of~5.3 ms(typical).Tens of solar radio bursts have been observed successfully during the period of the trial observation,demonstrating the system's ability to detect fine structures with high spectral and temporal resolution.In this article,we present the design,implementation,and initial observational results of the decametric solar radio spectrometer system in detail.展开更多
Spectral classification plays a crucial role in the analysis of astronomical data.Currently,stellar spectral classification primarily relies on one-dimensional(1D)spectra and necessitates a sufficient signal-to-noise ...Spectral classification plays a crucial role in the analysis of astronomical data.Currently,stellar spectral classification primarily relies on one-dimensional(1D)spectra and necessitates a sufficient signal-to-noise ratio(S/N).However,in cases where the S/N is low,obtaining valuable information becomes impractical.In this paper,we propose a novel model called DRC-Net(Double-branch celestial spectral classification network based on residual mechanisms)for stellar classification,which operates solely on two-dimensional(2D)spectra.The model consists of two branches that use 1D convolutions to reduce the dimensionality of the 2D spectral composed of both blue and red arms.In the following,the features extracted from both branches are fused,and the fused result undergoes further feature extraction before being fed into the classifier for final output generation.The data set is from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope,comprising 15,680 spectra of F,G,and K types.The preprocessing process includes normalization and the early stopping mechanism.The experimental results demonstrate that the proposed DRC-Net achieved remarkable classification precision of 93.0%,83.5%,and86.9%for F,G,and K types,respectively,surpassing the performance of 1D spectral classification methods.Furthermore,different S/N intervals are tested to judge the classification ability of DRC-Net.The results reveal that DRC-Net,as a 2D spectral classification model,can deliver superior classification outcomes for the spectra with low S/Ns.These experimental findings not only validate the efficiency of DRC-Net but also confirm the enhanced noise resistance ability exhibited by 2D spectra.展开更多
In this paper,we report a real-time Fast Radio Burst(FRB)searching system that has been successfully implemented with the 19 beam receiver of the Five-hundred-meter Aperture Spherical radio Telescope(FAST).The relativ...In this paper,we report a real-time Fast Radio Burst(FRB)searching system that has been successfully implemented with the 19 beam receiver of the Five-hundred-meter Aperture Spherical radio Telescope(FAST).The relatively small field of view of FAST makes the search for new FRBs challenging,but its high sensitivity significantly improves the accuracy of FRB localization and enables the detection of high-precision neutral hydrogen absorption lines generated by FRBs.Our goal is to develop an FRB searching system capable of realtime detection of FRBs that allows high-time resolution spectro-temporal studies among the repeated bursts,as well as detailed investigations of these bursts and exploration of FRB progenitor models.The data from each beam of the 19-beam receiver are fed into a high-performance computing node server,which performs real-time searches for pulses with a wide dispersion measure(DM)range of 20–10,000 pc cm^(-3) with step efficiency of 25%in real time.Then,the head node server aggregates all the candidate signals from each beam within a given time,determining their authenticity based on various criteria,including arrival time,pulse width,signal-to-noise ratio and coincidence patterns among the 19 beams.Within the 1.05–1.45 GHz operating bandwidth of the FAST 19beam receiver,the system achieves a frequency resolution of 122.07 kHz and a time resolution of 270.336μs.Subsequently,our team detected a series of bursts with a DM of 566 on 2019 August 30 confirming them as FRB121102.The FRB searching system enables the 19-beam receiver of FAST to detect repeated/one-off pulses/bursts in real time.展开更多
基金supported by the Joint Research Fund in Astronomy (U1531242) under cooperative agreement between the National Natural Science Foundation of China (NSFC) and Chinese Academy of Sciences (CAS)the NSFC (No. 11673036)+1 种基金the Interdiscipline Research Funds of Beijing Normal UniversityFunding for the project has been provided by the National Development and Reform Commission
文摘We use the Richardson-Lucy deconvolution algorithm to extract one-dimensional(1 D) spectra from Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST) spectrum images. Compared with other deconvolution algorithms, this algorithm is much faster. The application on a real LAMOST image illustrates that the 1 D spectrum resulting from this method has a higher signal-to-noise ratio and resolution than those extracted by the LAMOST pipeline. Furthermore, our algorithm can effectively suppress the ringings that are often present in the 1 D resulting spectra generated by other deconvolution methods.
基金supported by the National Natural Science Foundation of China(NSFC)grants 11703089 and 11903080the support by the National SKA Program of China(No.2022SKA0120101)+2 种基金Yunnan Fundamental Research Projects(No.202301AT070325)the support by Kunming International Cooperation Base Project(GHJD-2021022)the support of Yunnan Key Laboratory of Solar physics and Space Science,Kunming(202205AG070009)。
文摘The dynamic spectral observation at decametric wavelength is important to study solar radio physics and space weather.However,the observing system is difficult to observe with high sensitivity at this band due to the fact that the system temperature is dominated by the sky background noise and the antenna is difficult to design with high gain.An effective solution to improve the sensitivity is constructing an antenna array based on the beamforming method.Accordingly,we develop a decametric solar radio spectrometer system based on a 4-element beamforming array.The system consists of four antennas,an 8-channel analog receiver and a digital receiver.We use the true time delay to implement the beamformer and the classical FFT method to perform spectrum analysis in the digital receiver.Operating at a frequency range of 25–65 MHz with dual-circular polarizations,the system provides high resolution dynamic spectrum with spectral resolution of~12 kHz and temporal resolution of~5.3 ms(typical).Tens of solar radio bursts have been observed successfully during the period of the trial observation,demonstrating the system's ability to detect fine structures with high spectral and temporal resolution.In this article,we present the design,implementation,and initial observational results of the decametric solar radio spectrometer system in detail.
基金supported by the Natural Science Foundation of Tianjin Municipality(22JCYBJC00410)the National Natural Science Foundation of China-Chinese Academy of Sciences Joint Fund for Astronomy(U1931134)。
文摘Spectral classification plays a crucial role in the analysis of astronomical data.Currently,stellar spectral classification primarily relies on one-dimensional(1D)spectra and necessitates a sufficient signal-to-noise ratio(S/N).However,in cases where the S/N is low,obtaining valuable information becomes impractical.In this paper,we propose a novel model called DRC-Net(Double-branch celestial spectral classification network based on residual mechanisms)for stellar classification,which operates solely on two-dimensional(2D)spectra.The model consists of two branches that use 1D convolutions to reduce the dimensionality of the 2D spectral composed of both blue and red arms.In the following,the features extracted from both branches are fused,and the fused result undergoes further feature extraction before being fed into the classifier for final output generation.The data set is from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope,comprising 15,680 spectra of F,G,and K types.The preprocessing process includes normalization and the early stopping mechanism.The experimental results demonstrate that the proposed DRC-Net achieved remarkable classification precision of 93.0%,83.5%,and86.9%for F,G,and K types,respectively,surpassing the performance of 1D spectral classification methods.Furthermore,different S/N intervals are tested to judge the classification ability of DRC-Net.The results reveal that DRC-Net,as a 2D spectral classification model,can deliver superior classification outcomes for the spectra with low S/Ns.These experimental findings not only validate the efficiency of DRC-Net but also confirm the enhanced noise resistance ability exhibited by 2D spectra.
基金the International Partnership Program of the Chinese Academy of Sciences No.114A11-KYSB20200029the National Natural Science Foundation of China(NSFC,Grant No.12041301)the National Key R&D Program of China No.2020YC2201700。
文摘In this paper,we report a real-time Fast Radio Burst(FRB)searching system that has been successfully implemented with the 19 beam receiver of the Five-hundred-meter Aperture Spherical radio Telescope(FAST).The relatively small field of view of FAST makes the search for new FRBs challenging,but its high sensitivity significantly improves the accuracy of FRB localization and enables the detection of high-precision neutral hydrogen absorption lines generated by FRBs.Our goal is to develop an FRB searching system capable of realtime detection of FRBs that allows high-time resolution spectro-temporal studies among the repeated bursts,as well as detailed investigations of these bursts and exploration of FRB progenitor models.The data from each beam of the 19-beam receiver are fed into a high-performance computing node server,which performs real-time searches for pulses with a wide dispersion measure(DM)range of 20–10,000 pc cm^(-3) with step efficiency of 25%in real time.Then,the head node server aggregates all the candidate signals from each beam within a given time,determining their authenticity based on various criteria,including arrival time,pulse width,signal-to-noise ratio and coincidence patterns among the 19 beams.Within the 1.05–1.45 GHz operating bandwidth of the FAST 19beam receiver,the system achieves a frequency resolution of 122.07 kHz and a time resolution of 270.336μs.Subsequently,our team detected a series of bursts with a DM of 566 on 2019 August 30 confirming them as FRB121102.The FRB searching system enables the 19-beam receiver of FAST to detect repeated/one-off pulses/bursts in real time.
