The proposed design of a microwave superconducting kinetic inductance detector(MKID)array readout system characterizes the performance of MKIDs through a digital homodyne frequency mixing architecture.Meanwhile,the re...The proposed design of a microwave superconducting kinetic inductance detector(MKID)array readout system characterizes the performance of MKIDs through a digital homodyne frequency mixing architecture.Meanwhile,the readout system is implemented using a frequency division multiplexing circuit system,coupled with an FFT design to enable the readout of MKID arrays.The system is characterized by its compact size,low cost,portability,and ease of further development.Together,these features have significant implications for the design and readout of terahertz MKID arrays,while simultaneously advancing both the theoretical and practical aspects of MKID technology.展开更多
To further improve the pointing accuracy of altazimuth telescopes,this study takes the NAOC 2.5 m telescope as the research object and develops a comprehensive pointing model.The paper rst analyzes the causes of error...To further improve the pointing accuracy of altazimuth telescopes,this study takes the NAOC 2.5 m telescope as the research object and develops a comprehensive pointing model.The paper rst analyzes the causes of errors and accordingly constructs three core models:the basic parametric model,the spherical harmonic model,and the polynomial regression model.Among them,the basic parametric model aims to t error terms with clear physical meanings,but its correction capability is limited and cannot fully cover all in uencing factors.To address this limitation,a spherical harmonic model is introduced.This model demonstrates excellent performance in handling higher-order error terms and can accurately t errors across the celestial sphere.Additionally,a polynomial regression model is designed to improve the tting capability and prediction accuracy for nonlinear errors by exibly adjusting the polynomial order.The resulting comprehensive pointing model combines the advantages of these three models,enabling more precise and complete correction of pointing errors while balancing computational complexity and accuracy by adjusting the tting weight of each model.Experimental veri cation shows that the telescope’s pointing accuracy is improved from 17".805 to 3".1029,meeting the requirements for high-precision astronomical observations.展开更多
The infrared band contains rich opportunities for astronomical research,but due to the limitations of infrared technology,the development of infrared astronomy in China has been far from satisfactory for a long time,e...The infrared band contains rich opportunities for astronomical research,but due to the limitations of infrared technology,the development of infrared astronomy in China has been far from satisfactory for a long time,especially for solar observation.“Accurate Infrared Magnetic field Measurements of the Sun”project(AIMS)is a National Major Scientific Research Instrument Development Project(recommended by the Ministries)supported by the National Natural Science Foundation of China.It is aimed at improving the accuracy of magnetic field measurement by an order of magnitude,by measuring the“Zeeman splitting”directly.In addition,as AIMS is also the first equipment specifically designed for mid-to far-infrared solar observation in the world,we also hope to utilize AIMS to explore potential new scientific research opportunities in the vast infrared region.This article will briefly introduce the scientific objectives,the telescope,the scientific post-focus instruments,and finally summarize the commissioning observations of AIMS.展开更多
The SiTian project,with its vast field of view,will become an ideal platform for scientific research on asteroids.In this study,we develop a pipeline to analyze the photometry of asteroids and derive their periods fro...The SiTian project,with its vast field of view,will become an ideal platform for scientific research on asteroids.In this study,we develop a pipeline to analyze the photometry of asteroids and derive their periods from the data collected by the SiTian pathfinder project Mini-SiTian(MST).The pipeline is applied to the MST f02 region,an MST test region with a sky area of 2°.29×1°.53.Rotation periods of 22 asteroids are derived by the obtained light curve analysis.Among them,there are eight asteroids available in the Asteroid Lightcurve Photometry Database(ALCDEF),and six of them with more photometric points(>200)that have similar period parameters as the ones in ALCDEF.Additionally,the periods for 14 of these asteroids are newly obtained and are not listed in ALCDEF.This study demonstrates the feasibility of asteroid photometric research by the SiTian project.It shows that future observations from the SiTian project will provide even more photometry of asteroids,significantly increasing the number of available light curves.The potential vast photometric data on asteroids will help us to further understand the physics of asteroids,their material composition,and the formation and evolution of the solar system.展开更多
The axion,a leading dark matter(DM)candidate,can convert to photons in neutron star(NS)magnetospheres via the Primakoff effect,producing narrow-band radio emission that may be detected with high-sensitivity radio tele...The axion,a leading dark matter(DM)candidate,can convert to photons in neutron star(NS)magnetospheres via the Primakoff effect,producing narrow-band radio emission that may be detected with high-sensitivity radio telescopes.Previous studies searched for axion DM-induced signals from the isolated NS J0806.4-4123 using observations of the Meer KAT UHF band(544–1088 MHz),but excluded the 1051–1088 MHz subband to mitigate potential sideband contamination.To probe this unexplored parameter space,we reprocessed the 1000–1088 MHz subband data using optimized radio frequency interference(RFI)flagging and meticulous sideband calibration.The flux stability of the calibrators and the consistency with Meer KAT’s system equivalent flux density confirmed the reliability of the data within the 1000–1080 MHz range,while the 1080–1088 MHz subband was omitted due to flux anomalies.No significant signals exceeding 5σsignificance were detected within the axion mass range of 4.136–4.467μe V(1000–1080 MHz),including the previously unprobed range 4.347–4.467μe V(1051–1080 MHz).Our null detection sets new stringent constraints with Meer KAT NS data,excluding axion-photon couplings|g_(aγγ)|?8.2×10^(-12)Ge V^(-1)at the 95%confidence level for DM masses between 4.347 and 4.467μe V.展开更多
The SiTian Project represents a groundbreaking initiative in astronomy,aiming to deploy a global network of telescopes,each with a 1 m aperture,for comprehensive time-domain sky surveys.The network's innovative ar...The SiTian Project represents a groundbreaking initiative in astronomy,aiming to deploy a global network of telescopes,each with a 1 m aperture,for comprehensive time-domain sky surveys.The network's innovative architecture features multiple observational nodes,each comprising three strategically aligned telescopes equipped with filters.This design enables three-color(g,r,i)channel imaging within each node,facilitating precise and coordinated observations.As a pathfinder to the full-scale project,the Mini-SiTian Project serves as the scientific and technological validation platform,utilizing three 30 cm aperture telescopes to validate the methodologies and technologies planned for the broader SiTian network.This paper focuses on the development and implementation of the Master Control System(MCS),and the central command hub for the Mini-SiTian Array.The MCS is designed to facilitate seamless communication with the SiTian Brain,the project's central processing and decisionmaking unit,while ensuring accurate task allocation,real-time status monitoring,and optimized observational workflows.The system adopts a robust architecture that separates front-end and back-end functionalities.A key innovation of the MCS is its ability to dynamically adjust observation plans in response to transient source alerts,enabling rapid and coordinated scans of target sky regions.The paper provides an in-depth analysis of the system's internal components,including the communication system,which is critical for seamless network operation.Extensive testing has validated the functionality,reliability,and compatibility of these components within the overall system architecture.The successful deployment of the MCS in managing the Mini-SiTian Array has demonstrated its practicality and efficacy in collaborative observation and distributed control.By simplifying cluster management and ensuring data integrity,the MCS represents a significant advancement in astronomical observation control systems.Its scalable and adaptable design not only supports the future expansion of the SiTian network but also provides a blueprint for other large-scale telescope arrays,marking a transformative step forward in time-domain astronomy.展开更多
The inner Milky Way disk globular cluster NGC 6362 appears to exhibit tidal tails composed of stars that have proper motions and positions in the color–magnitude diagram similar to those of cluster stars. Because rec...The inner Milky Way disk globular cluster NGC 6362 appears to exhibit tidal tails composed of stars that have proper motions and positions in the color–magnitude diagram similar to those of cluster stars. Because recent results seem also to show that these stars are distributed across the regions least affected by interstellar absorption and reproduce the observed composite star field density map, we carried out a detailed spectroscopic analysis of a number of chemical element abundances of tidal tail star candidates in order to investigate the relationship between them and NGC 6362. From European Southern Observatory's VLT@FLAMES spectra we found that the red giant branch stars selected as the cluster's tidal tail stars neither have overall metallicities nor abundances of Mg, Ca, Sc, Ti, Cr, Ni and Ba similar to the cluster's ones. Moreover, they are mainly alike to stars that belong to the Milky Way thick disk, some of them could be part of the thin disk and a minor percentage could belong to the Milky Way halo star population. On the other hand, since the resulting radial velocities do not exhibit a distribution function similar to that of the cluster's stars, we concluded that looking for kinematic properties similar to those of the cluster would not seem to be as suitable of an approach for selecting the cluster's tidal tail stars as previously thought.展开更多
The solar radio signal that can be received by the ground-based telescopes covers a wide frequency range,allowing us to monitor the complex physical processes occurred from the solar surface to the vast interplanetary...The solar radio signal that can be received by the ground-based telescopes covers a wide frequency range,allowing us to monitor the complex physical processes occurred from the solar surface to the vast interplanetary space.MingantU SpEctral Radioheliograph(MUSER),as the latest generation of solar dedicated radio spectral-imaging instrument in the centimeter-decimeter wavelengths,has accumulated a large number of observational data since its commissioning observation in 2014.This paper presents the main observational results identified by MUSER from 2014 to 2019,including the quiet Sun and 94 solar radio burst events.We find that there are 81 events accompanied with Geostationary Operational Environmental Satellites(GOES)soft X-ray(SXR)flares,among which the smallest flare class is B1.0.There are 13 events without accompanying any recorded flares,among which the smallest SXR intensity during the radio burst period is equivalent to level-A.The main characteristics of all radio burst events are presented,which shows the powerful ability of MUSER to capture the valuable information of the solar non-thermal processes and the importance for space weather.This work also provides a database for further in-depth research.展开更多
When there exists anisotropy in underground media elastic parameters of the observed coordinate possibly do not coincide with that of the natural coordinate. According to the theory that the density of potential energ...When there exists anisotropy in underground media elastic parameters of the observed coordinate possibly do not coincide with that of the natural coordinate. According to the theory that the density of potential energy, dissipating energy is independent of the coordinate, the relationship of elastic parameters between two coordinates is derived for two-phase anisotropic media. Then, pseudospectral method to solve wave equations of two-phase anisotropic media is derived. At last, we use this method to simulate wave propagation in two-phase anisotropic media four types of waves are observed in the snapshots, i.e., fast P wave and slow P wave, fast S wave and slow S wave. Shear wave splitting, SV wave cusps and elastic wave reflection and transmission are also observed.展开更多
By employing the previous Voronoi approach and replacing its nearest neighbor approx- imation with Drizzle in iterative signal extraction, we develop a fast iterative Drizzle algorithm, namedfiDrizzle, to reconstruct ...By employing the previous Voronoi approach and replacing its nearest neighbor approx- imation with Drizzle in iterative signal extraction, we develop a fast iterative Drizzle algorithm, namedfiDrizzle, to reconstruct the underlying band-limited image from undersampled dithered frames. Compared with the existing iDrizzle, the new algorithm improves rate of convergence and accelerates the computational speed. Moreover, under the same conditions （e.g. the same number of dithers and iterations）, fiDrizzle can make a better quality reconstruction than iDrizzle, due to the newly discov- ered High Sampling caused Decelerating Convergence （HSDC） effect in the iterative signal extraction process.fiDrizzle demonstrates its powerful ability to perform image deconvolution from undersampled dithers.展开更多
The paper describes observations of fast-moving near-Earth asteroids(NEAs) made with the small ground-based telescopes of National Time Service Center of Chinese Academy of Science(NTSC of CAS) and Research Institute ...The paper describes observations of fast-moving near-Earth asteroids(NEAs) made with the small ground-based telescopes of National Time Service Center of Chinese Academy of Science(NTSC of CAS) and Research Institute "Mykolaiv Astronomical Observatory"(RI MAO) by the rotating-drift-scan CCD(RDS CCD) technique. This technique is used to obtain the point images of both the studied objects and reference stars. The results of ongoing follow-up observations of NEAs are discussed. The residual differences(O-C) between the observed and calculated positions from JPL ephemeris were generally small for these asteroids. The standard deviations of these differences were typically ±(0.2′′-0.3′′) in both coordinates for objects with apparent velocity which substantially exceed FWHM for the given exposure time. The results of comparative statistics for such observations from the MPC database show that this is a good level of precision for NEAs. Moreover, the telescopes with the RDS CCD technique implemented can observe the NEAs that closely approach the Earth and with enough observations can improve the precision of determining their orbital elements and impact predictions.展开更多
Radioheliograph images are essential for the study of solar short term activities and long term variations, while the continuity and granularity of radioheliograph data are not so ideal, due to the short visible time ...Radioheliograph images are essential for the study of solar short term activities and long term variations, while the continuity and granularity of radioheliograph data are not so ideal, due to the short visible time of the Sun and the complex electron-magnetic environment near the ground-based radio telescope. In this work, we develop a multi-channel input single-channel output neural network, which can generate radioheliograph image in microwave band from the Extreme Ultra-violet(EUV) observation of the Atmospheric Imaging Assembly(AIA) on board the Solar Dynamic Observatory(SDO). The neural network is trained with nearly 8 years of data of Nobeyama Radioheliograph(No RH) at 17 GHz and SDO/AIA from January 2011 to September 2018. The generated radioheliograph image is in good consistency with the well-calibrated No RH observation. SDO/AIA provides solar atmosphere images in multiple EUV wavelengths every 12 seconds from space, so the present model can fill the vacancy of limited observation time of microwave radioheliograph, and support further study of the relationship between the microwave and EUV emission.展开更多
The geometric distortion of a CCD field of view has a direct influence on the positional measurements of CCD observations. In order to obtain high precision astrometric results, the geometric distortion should be deri...The geometric distortion of a CCD field of view has a direct influence on the positional measurements of CCD observations. In order to obtain high precision astrometric results, the geometric distortion should be derived and corrected precisely. As presented in our previous work, a convenient solution has been carried out and has also been applied to observations of Phoebe. In order to fur- ther improve the solution, an orthogonal method based on Zernike polynomials is used in this work. Four nights of CCD observations including Himalia, the sixth satellite of Jupiter, and open clusters （NGC 1664 or NGC 2324） on each night have been processed as an application. The observations were obtained from the 2.4 m telescope administered by Yunnan Observatories. The catalog UCAC4 was used to match reference stars in all of the CCD frames. The ephemeris of Himalia is retrieved from the Institut de M6canique C61este et de Calcul des Ephemerides （IMCCE）. Our results show that the means of observed minus calculated （O - C） positional residuals are -0.034 and -0.026 arcsec in right ascension and declination, respectively. The corresponding standard deviations are 0.031＂ and 0.028＂. The measurement dispersion is significantly improved compared to that by using our previous solution.展开更多
The basic physical parameters of asteroids, such as spin parameters, shape and scattering parameters, can provide us with information on the formation and evolution of both the asteroids themselves and the entire sola...The basic physical parameters of asteroids, such as spin parameters, shape and scattering parameters, can provide us with information on the formation and evolution of both the asteroids themselves and the entire solar system. In a majority of asteroids, the disk-integrated photometry measurement constitutes the primary source of the above knowledge. In the present paper, newly observed photometric data and existing data on（585） Bilkis are analyzed based on a Lommel-Seeliger ellipsoid model. With a Markov chain Monte Carlo（MCMC） method, we have determined the spin parameters（period, pole orientation）and shape（b/a, c/a） of（585） Bilkis and their uncertainties. As a result, we obtained a rotational period of 8.5738209 h with an uncertainty of 9×10^-7h, and derived a pole of（136.46°, 29.0°） in the ecliptic frame of J2000.0 with uncertainties of 0.67°and 1.1°in longitude and latitude respectively. We also derived triaxial ratios b/a and c/a of（585） Bilkis as 0.736 and 0.70 with uncertainties of 0.003 and 0.03 respectively.展开更多
Lunar optical polarization is a fascinating phenomenon that occurs when sunlight reflects off the surface of the Moon and becomes polarized.This study employs a novel split-focus plane polarimetric camera to conduct t...Lunar optical polarization is a fascinating phenomenon that occurs when sunlight reflects off the surface of the Moon and becomes polarized.This study employs a novel split-focus plane polarimetric camera to conduct the initial white light polarimetric observations on the near side of the Moon.We obtained the linear degree of polarization(DOP)parameters of white light by observation from the eastern and western hemispheres of the Moon.The findings indicate that the white light polarization is lower in the lunar highland than in the lunar maria overall.Combining the analysis of lunar soil samples,we noticed and determined that the DOP parameters of white light demonstrate high consistency with iron oxide on the Moon.This study may serve as a new diagnostic tool for the Moon.展开更多
The radioheliograph is an extensive array of antennas operating on the principle of aperture synthesis to produce images of the Sun.The image acquired by the telescope results from convoluting the Sun’s true brightne...The radioheliograph is an extensive array of antennas operating on the principle of aperture synthesis to produce images of the Sun.The image acquired by the telescope results from convoluting the Sun’s true brightness distribution with the antenna array’s directional pattern.The imaging quality of the radioheliograph is affected by a multitude of factors,with the performance of the“dirty beam”being simply one component.Other factors such as imaging methods,calibration techniques,clean algorithms,and more also play a significant influence on the resulting image quality.As the layout of the antenna array directly affects the performance of the dirty beam,the design of an appropriate antenna configuration is critical to improving the imaging quality of the radioheliograph.Based on the actual needs of observing the Sun,this work optimized the antenna array design and proposed a twodimensional low-redundancy array.The proposed array was compared with common T-shaped arrays,Y-shaped arrays,uniformly spaced circular arrays,and three-arm spiral arrays.Through simulations and experiments,their performance in terms of sampling point numbers,UV coverage area,beam-half width,sidelobe level,and performance in the absence of antennas are compared and analyzed.It was found that each of these arrays has its advantages,but the two-dimensional low-redundancy array proposed in this paper performs best in overall evaluation.It has the shortest imaging calculation time among the array types and is highly robust when antennas are missing,making it the most suitable choice.展开更多
Realtime trigger and localization of bursts are the key functions of GECAM,an all-sky gamma-ray monitor launched on 2020 December 10.We developed a multifunctional trigger and localization software operating in the CP...Realtime trigger and localization of bursts are the key functions of GECAM,an all-sky gamma-ray monitor launched on 2020 December 10.We developed a multifunctional trigger and localization software operating in the CPU of the GECAM Electronic Box.This onboard software has the following features:high trigger efficiency for real celestial bursts with a suppression of false triggers caused by charged particle bursts and background fluctuation,dedicated localization algorithm optimized for both short and long bursts,and low time latency of the trigger information which is downlinked through the Global Short Message Communication service of the global BeiDou navigation system.This paper provides a detailed description of the design and development of the trigger and localization software system for GECAM.It covers the general design,workflow,the main functions,and the algorithms used in the system.The paper also includes on-ground trigger tests using simulated gamma-ray bursts generated by a dedicated X-ray tube,as well as an overview of the performance for real celestial bursts during its in-orbit operation.展开更多
With great advance of ground-based extensive air shower arrays,such as LHAASO and HAWC,many very high energy(VHE)gamma-ray sources have been discovered and are being monitored regardless of the day and the night.Hence...With great advance of ground-based extensive air shower arrays,such as LHAASO and HAWC,many very high energy(VHE)gamma-ray sources have been discovered and are being monitored regardless of the day and the night.Hence,the Sun and Moon would have some impacts on the observation of gamma-ray sources,which have not been taken into account in previous analysis.In this paper,the influence of the Sun and Moon on the observation of very high energy gamma-ray sources when they are near the line of sight of the Sun or Moon is estimated.The tracks of all the known VHE sources are scanned and several VHE sources are found to be very close to the line of sight of the Sun or Moon during some period.The absorption of very high energy gamma rays by sunlight is estimated with detailed method and some useful conclusions are achieved.The main influence is the block of the Sun and Moon on gamma rays and the shadow on the cosmic ray background.The influence is investigated considering the detector angular resolution and some strategies on data analysis are proposed to avoid the underestimation of the gamma-ray emission.展开更多
The initial condition of high-mass star formation is a complex area of study because of the high densities(n_(H_(2))>106cm^(-3))and low temperatures(T_(dust)<18 K)involved.Under such conditions,many molecules be...The initial condition of high-mass star formation is a complex area of study because of the high densities(n_(H_(2))>106cm^(-3))and low temperatures(T_(dust)<18 K)involved.Under such conditions,many molecules become depleted from the gas phase by freezing out onto dust grains.However,the N-bearing and deuterated species could remain gaseous under these extreme conditions,suggesting that they may serve as ideal tracers.In this paper,using the Plateau de Bure Interferometer and Very Large Array observations at 1.3 mm,3.5 mm,and 1.3 cm,we investigate the possible habitats for NH_(3),NH_(2)D,H^(13)CN,HC^(15)N,SO,and C^(18)O in eight massive precluster and protocluster clumps G18.17,G18.21,G23.97N,G23.98,G23.44,G23.97S,G25.38,and G25.71.We found that the NH3cores are in good agreement with the 3.5 mm peak emission,but the NH_(3)is much more extended than the 3.5 mm emission structure.The SO distributions agree well with the 3.5 mm peaks for the evolved star formation stage,but we did not detect any SO emission in the four earliest star formation sources.C^(18)O is a poor tracer in conditions of the cold(■18 K)and dense(■10^(4)cm^(-3))cores,e.g.,the prestellar cores.We also found that the NH_(2)D cores are mainly located in the temperature range of 13.0-20.0 K,and the NH_(2)D lines may be strongly depleted above 20 K.展开更多
基金funded by the National Key Research and Development Program of China under Nos.2023YFA1608200&2020YFC2201703the National Natural Science Foundation of China(NSFC,Grant No.12020101002)the Natural Science Foundation of China for the youth under No.12103093。
文摘The proposed design of a microwave superconducting kinetic inductance detector(MKID)array readout system characterizes the performance of MKIDs through a digital homodyne frequency mixing architecture.Meanwhile,the readout system is implemented using a frequency division multiplexing circuit system,coupled with an FFT design to enable the readout of MKID arrays.The system is characterized by its compact size,low cost,portability,and ease of further development.Together,these features have significant implications for the design and readout of terahertz MKID arrays,while simultaneously advancing both the theoretical and practical aspects of MKID technology.
文摘To further improve the pointing accuracy of altazimuth telescopes,this study takes the NAOC 2.5 m telescope as the research object and develops a comprehensive pointing model.The paper rst analyzes the causes of errors and accordingly constructs three core models:the basic parametric model,the spherical harmonic model,and the polynomial regression model.Among them,the basic parametric model aims to t error terms with clear physical meanings,but its correction capability is limited and cannot fully cover all in uencing factors.To address this limitation,a spherical harmonic model is introduced.This model demonstrates excellent performance in handling higher-order error terms and can accurately t errors across the celestial sphere.Additionally,a polynomial regression model is designed to improve the tting capability and prediction accuracy for nonlinear errors by exibly adjusting the polynomial order.The resulting comprehensive pointing model combines the advantages of these three models,enabling more precise and complete correction of pointing errors while balancing computational complexity and accuracy by adjusting the tting weight of each model.Experimental veri cation shows that the telescope’s pointing accuracy is improved from 17".805 to 3".1029,meeting the requirements for high-precision astronomical observations.
文摘The infrared band contains rich opportunities for astronomical research,but due to the limitations of infrared technology,the development of infrared astronomy in China has been far from satisfactory for a long time,especially for solar observation.“Accurate Infrared Magnetic field Measurements of the Sun”project(AIMS)is a National Major Scientific Research Instrument Development Project(recommended by the Ministries)supported by the National Natural Science Foundation of China.It is aimed at improving the accuracy of magnetic field measurement by an order of magnitude,by measuring the“Zeeman splitting”directly.In addition,as AIMS is also the first equipment specifically designed for mid-to far-infrared solar observation in the world,we also hope to utilize AIMS to explore potential new scientific research opportunities in the vast infrared region.This article will briefly introduce the scientific objectives,the telescope,the scientific post-focus instruments,and finally summarize the commissioning observations of AIMS.
基金supports from the National Natural Science Foundation of China(NSFC,grant Nos.12203002 and 11973015)supports from the National Key Basic R&D Program of China via 2023YFA1608303 and the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB0550103)+6 种基金supports from the National Natural Science Foundation of China(NSFCgrant No.12373015)supports from the National Natural Science Foundation of China(NSFCgrant Nos.12120101003 and 12373010)National Key R&D Program of China(grant Nos.2023YFA1607800,2023YFA1607804,2022YFA1602902)Beijing Municipal Natural Science Foundation(grant No.1222028)Strategic Priority Research Program of the Chinese Academy of Science(grant Nos.XDB0550100 and XDB0550000).
文摘The SiTian project,with its vast field of view,will become an ideal platform for scientific research on asteroids.In this study,we develop a pipeline to analyze the photometry of asteroids and derive their periods from the data collected by the SiTian pathfinder project Mini-SiTian(MST).The pipeline is applied to the MST f02 region,an MST test region with a sky area of 2°.29×1°.53.Rotation periods of 22 asteroids are derived by the obtained light curve analysis.Among them,there are eight asteroids available in the Asteroid Lightcurve Photometry Database(ALCDEF),and six of them with more photometric points(>200)that have similar period parameters as the ones in ALCDEF.Additionally,the periods for 14 of these asteroids are newly obtained and are not listed in ALCDEF.This study demonstrates the feasibility of asteroid photometric research by the SiTian project.It shows that future observations from the SiTian project will provide even more photometry of asteroids,significantly increasing the number of available light curves.The potential vast photometric data on asteroids will help us to further understand the physics of asteroids,their material composition,and the formation and evolution of the solar system.
基金supported by the National Natural Science Foundation of China(NSFC,grant No.12220101003)the Leading Innovation and Entrepreneurship Team of Zhejiang Province of China(grant No.2023R01008)the National Key R&D Program of China No.2023YFE0110500。
文摘The axion,a leading dark matter(DM)candidate,can convert to photons in neutron star(NS)magnetospheres via the Primakoff effect,producing narrow-band radio emission that may be detected with high-sensitivity radio telescopes.Previous studies searched for axion DM-induced signals from the isolated NS J0806.4-4123 using observations of the Meer KAT UHF band(544–1088 MHz),but excluded the 1051–1088 MHz subband to mitigate potential sideband contamination.To probe this unexplored parameter space,we reprocessed the 1000–1088 MHz subband data using optimized radio frequency interference(RFI)flagging and meticulous sideband calibration.The flux stability of the calibrators and the consistency with Meer KAT’s system equivalent flux density confirmed the reliability of the data within the 1000–1080 MHz range,while the 1080–1088 MHz subband was omitted due to flux anomalies.No significant signals exceeding 5σsignificance were detected within the axion mass range of 4.136–4.467μe V(1000–1080 MHz),including the previously unprobed range 4.347–4.467μe V(1051–1080 MHz).Our null detection sets new stringent constraints with Meer KAT NS data,excluding axion-photon couplings|g_(aγγ)|?8.2×10^(-12)Ge V^(-1)at the 95%confidence level for DM masses between 4.347 and 4.467μe V.
基金Supported by National Key R&D Program of China(grant No.2023YFA1608304)Strategic Priority Research Program of the Chinese Academy of Sciences(XDB0550103)National Natural Science Foundation of China(NSFC,grant No.11903054)。
文摘The SiTian Project represents a groundbreaking initiative in astronomy,aiming to deploy a global network of telescopes,each with a 1 m aperture,for comprehensive time-domain sky surveys.The network's innovative architecture features multiple observational nodes,each comprising three strategically aligned telescopes equipped with filters.This design enables three-color(g,r,i)channel imaging within each node,facilitating precise and coordinated observations.As a pathfinder to the full-scale project,the Mini-SiTian Project serves as the scientific and technological validation platform,utilizing three 30 cm aperture telescopes to validate the methodologies and technologies planned for the broader SiTian network.This paper focuses on the development and implementation of the Master Control System(MCS),and the central command hub for the Mini-SiTian Array.The MCS is designed to facilitate seamless communication with the SiTian Brain,the project's central processing and decisionmaking unit,while ensuring accurate task allocation,real-time status monitoring,and optimized observational workflows.The system adopts a robust architecture that separates front-end and back-end functionalities.A key innovation of the MCS is its ability to dynamically adjust observation plans in response to transient source alerts,enabling rapid and coordinated scans of target sky regions.The paper provides an in-depth analysis of the system's internal components,including the communication system,which is critical for seamless network operation.Extensive testing has validated the functionality,reliability,and compatibility of these components within the overall system architecture.The successful deployment of the MCS in managing the Mini-SiTian Array has demonstrated its practicality and efficacy in collaborative observation and distributed control.By simplifying cluster management and ensuring data integrity,the MCS represents a significant advancement in astronomical observation control systems.Its scalable and adaptable design not only supports the future expansion of the SiTian network but also provides a blueprint for other large-scale telescope arrays,marking a transformative step forward in time-domain astronomy.
基金Based on observations collected at the European Southern Observatory under ESO program(s)113.2661.001.
文摘The inner Milky Way disk globular cluster NGC 6362 appears to exhibit tidal tails composed of stars that have proper motions and positions in the color–magnitude diagram similar to those of cluster stars. Because recent results seem also to show that these stars are distributed across the regions least affected by interstellar absorption and reproduce the observed composite star field density map, we carried out a detailed spectroscopic analysis of a number of chemical element abundances of tidal tail star candidates in order to investigate the relationship between them and NGC 6362. From European Southern Observatory's VLT@FLAMES spectra we found that the red giant branch stars selected as the cluster's tidal tail stars neither have overall metallicities nor abundances of Mg, Ca, Sc, Ti, Cr, Ni and Ba similar to the cluster's ones. Moreover, they are mainly alike to stars that belong to the Milky Way thick disk, some of them could be part of the thin disk and a minor percentage could belong to the Milky Way halo star population. On the other hand, since the resulting radial velocities do not exhibit a distribution function similar to that of the cluster's stars, we concluded that looking for kinematic properties similar to those of the cluster would not seem to be as suitable of an approach for selecting the cluster's tidal tail stars as previously thought.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11790301, 11790305, 11973057, 12003048, 11903055, 11773043 and 12003049)supported by the Ministry of Science and Technology of China Key Project (2018YFA0404602)the international collaboration of ISSI-BJ
文摘The solar radio signal that can be received by the ground-based telescopes covers a wide frequency range,allowing us to monitor the complex physical processes occurred from the solar surface to the vast interplanetary space.MingantU SpEctral Radioheliograph(MUSER),as the latest generation of solar dedicated radio spectral-imaging instrument in the centimeter-decimeter wavelengths,has accumulated a large number of observational data since its commissioning observation in 2014.This paper presents the main observational results identified by MUSER from 2014 to 2019,including the quiet Sun and 94 solar radio burst events.We find that there are 81 events accompanied with Geostationary Operational Environmental Satellites(GOES)soft X-ray(SXR)flares,among which the smallest flare class is B1.0.There are 13 events without accompanying any recorded flares,among which the smallest SXR intensity during the radio burst period is equivalent to level-A.The main characteristics of all radio burst events are presented,which shows the powerful ability of MUSER to capture the valuable information of the solar non-thermal processes and the importance for space weather.This work also provides a database for further in-depth research.
文摘When there exists anisotropy in underground media elastic parameters of the observed coordinate possibly do not coincide with that of the natural coordinate. According to the theory that the density of potential energy, dissipating energy is independent of the coordinate, the relationship of elastic parameters between two coordinates is derived for two-phase anisotropic media. Then, pseudospectral method to solve wave equations of two-phase anisotropic media is derived. At last, we use this method to simulate wave propagation in two-phase anisotropic media four types of waves are observed in the snapshots, i.e., fast P wave and slow P wave, fast S wave and slow S wave. Shear wave splitting, SV wave cusps and elastic wave reflection and transmission are also observed.
基金supported by the National Basic Research Program of China (973 program, Nos. 2015CB857000 and 2013CB834900)the Foundation for Distinguished Young Scholars of Jiangsu Province (No. BK20140050)+1 种基金the ‘Strategic Priority Research Program the Emergence of Cosmological Structure’ of the CAS (No. XDB09010000)the National Natural Science Foundation of China (Nos. 11333008, 11233005, 11273061 and 11673065)
文摘By employing the previous Voronoi approach and replacing its nearest neighbor approx- imation with Drizzle in iterative signal extraction, we develop a fast iterative Drizzle algorithm, namedfiDrizzle, to reconstruct the underlying band-limited image from undersampled dithered frames. Compared with the existing iDrizzle, the new algorithm improves rate of convergence and accelerates the computational speed. Moreover, under the same conditions （e.g. the same number of dithers and iterations）, fiDrizzle can make a better quality reconstruction than iDrizzle, due to the newly discov- ered High Sampling caused Decelerating Convergence （HSDC） effect in the iterative signal extraction process.fiDrizzle demonstrates its powerful ability to perform image deconvolution from undersampled dithers.
基金supported by the National Natural Science Foundation of China(Grant Nos.U1831133 and 12073062)National Astronomical Data Center of China。
文摘The paper describes observations of fast-moving near-Earth asteroids(NEAs) made with the small ground-based telescopes of National Time Service Center of Chinese Academy of Science(NTSC of CAS) and Research Institute "Mykolaiv Astronomical Observatory"(RI MAO) by the rotating-drift-scan CCD(RDS CCD) technique. This technique is used to obtain the point images of both the studied objects and reference stars. The results of ongoing follow-up observations of NEAs are discussed. The residual differences(O-C) between the observed and calculated positions from JPL ephemeris were generally small for these asteroids. The standard deviations of these differences were typically ±(0.2′′-0.3′′) in both coordinates for objects with apparent velocity which substantially exceed FWHM for the given exposure time. The results of comparative statistics for such observations from the MPC database show that this is a good level of precision for NEAs. Moreover, the telescopes with the RDS CCD technique implemented can observe the NEAs that closely approach the Earth and with enough observations can improve the precision of determining their orbital elements and impact predictions.
基金supported by the National Natural Science Foundation of China(Grant Nos.41974199 and 41574167)the B-type Strategic Priority Program of the Chinese Academy of Sciences(XDB41000000)。
文摘Radioheliograph images are essential for the study of solar short term activities and long term variations, while the continuity and granularity of radioheliograph data are not so ideal, due to the short visible time of the Sun and the complex electron-magnetic environment near the ground-based radio telescope. In this work, we develop a multi-channel input single-channel output neural network, which can generate radioheliograph image in microwave band from the Extreme Ultra-violet(EUV) observation of the Atmospheric Imaging Assembly(AIA) on board the Solar Dynamic Observatory(SDO). The neural network is trained with nearly 8 years of data of Nobeyama Radioheliograph(No RH) at 17 GHz and SDO/AIA from January 2011 to September 2018. The generated radioheliograph image is in good consistency with the well-calibrated No RH observation. SDO/AIA provides solar atmosphere images in multiple EUV wavelengths every 12 seconds from space, so the present model can fill the vacancy of limited observation time of microwave radioheliograph, and support further study of the relationship between the microwave and EUV emission.
基金support from the staff at the Lijiang 2.4 m telescopeFunding for the telescope has been provided by CAS and the People’s Government of Yunnan Provincefinancially supported by the National Natural Science Foundation of China(Grant Nos.U1431227 and11273014)
文摘The geometric distortion of a CCD field of view has a direct influence on the positional measurements of CCD observations. In order to obtain high precision astrometric results, the geometric distortion should be derived and corrected precisely. As presented in our previous work, a convenient solution has been carried out and has also been applied to observations of Phoebe. In order to fur- ther improve the solution, an orthogonal method based on Zernike polynomials is used in this work. Four nights of CCD observations including Himalia, the sixth satellite of Jupiter, and open clusters （NGC 1664 or NGC 2324） on each night have been processed as an application. The observations were obtained from the 2.4 m telescope administered by Yunnan Observatories. The catalog UCAC4 was used to match reference stars in all of the CCD frames. The ephemeris of Himalia is retrieved from the Institut de M6canique C61este et de Calcul des Ephemerides （IMCCE）. Our results show that the means of observed minus calculated （O - C） positional residuals are -0.034 and -0.026 arcsec in right ascension and declination, respectively. The corresponding standard deviations are 0.031＂ and 0.028＂. The measurement dispersion is significantly improved compared to that by using our previous solution.
基金funded by the National Natural Science Foundation of China(Grant Nos.11073051 and 11473066)supported,in part,by the Academy of Finland(Project 1257966)
文摘The basic physical parameters of asteroids, such as spin parameters, shape and scattering parameters, can provide us with information on the formation and evolution of both the asteroids themselves and the entire solar system. In a majority of asteroids, the disk-integrated photometry measurement constitutes the primary source of the above knowledge. In the present paper, newly observed photometric data and existing data on（585） Bilkis are analyzed based on a Lommel-Seeliger ellipsoid model. With a Markov chain Monte Carlo（MCMC） method, we have determined the spin parameters（period, pole orientation）and shape（b/a, c/a） of（585） Bilkis and their uncertainties. As a result, we obtained a rotational period of 8.5738209 h with an uncertainty of 9×10^-7h, and derived a pole of（136.46°, 29.0°） in the ecliptic frame of J2000.0 with uncertainties of 0.67°and 1.1°in longitude and latitude respectively. We also derived triaxial ratios b/a and c/a of（585） Bilkis as 0.736 and 0.70 with uncertainties of 0.003 and 0.03 respectively.
基金supported by the National Key Research and Development Program of China(2021YFA0715101)partly supported by a National LLR station project+2 种基金the National Natural Science Foundation of China(NSFC,Grant Nos.11973064 and 42101413)Jilin Province Mid-youth science and technology innovation and entrepreneurship outstanding talent project(20220508147RC)the Changchun City and Chinese Academy of Sciences Science and Technology Cooperation High-tech Industrialization Special Fund Project(21SH05)。
文摘Lunar optical polarization is a fascinating phenomenon that occurs when sunlight reflects off the surface of the Moon and becomes polarized.This study employs a novel split-focus plane polarimetric camera to conduct the initial white light polarimetric observations on the near side of the Moon.We obtained the linear degree of polarization(DOP)parameters of white light by observation from the eastern and western hemispheres of the Moon.The findings indicate that the white light polarization is lower in the lunar highland than in the lunar maria overall.Combining the analysis of lunar soil samples,we noticed and determined that the DOP parameters of white light demonstrate high consistency with iron oxide on the Moon.This study may serve as a new diagnostic tool for the Moon.
基金supported by the grants of the National Natural Science Foundation of China(42127804,42374219)。
文摘The radioheliograph is an extensive array of antennas operating on the principle of aperture synthesis to produce images of the Sun.The image acquired by the telescope results from convoluting the Sun’s true brightness distribution with the antenna array’s directional pattern.The imaging quality of the radioheliograph is affected by a multitude of factors,with the performance of the“dirty beam”being simply one component.Other factors such as imaging methods,calibration techniques,clean algorithms,and more also play a significant influence on the resulting image quality.As the layout of the antenna array directly affects the performance of the dirty beam,the design of an appropriate antenna configuration is critical to improving the imaging quality of the radioheliograph.Based on the actual needs of observing the Sun,this work optimized the antenna array design and proposed a twodimensional low-redundancy array.The proposed array was compared with common T-shaped arrays,Y-shaped arrays,uniformly spaced circular arrays,and three-arm spiral arrays.Through simulations and experiments,their performance in terms of sampling point numbers,UV coverage area,beam-half width,sidelobe level,and performance in the absence of antennas are compared and analyzed.It was found that each of these arrays has its advantages,but the two-dimensional low-redundancy array proposed in this paper performs best in overall evaluation.It has the shortest imaging calculation time among the array types and is highly robust when antennas are missing,making it the most suitable choice.
基金supported by the Strategic Priority Research Program on Space Science of the Chinese Academy of Sciences,the support from the Strategic Priority Research Program on Space Science(grant Nos.XDA15360300,XDA15360000,XDA15360102,XDA15052700 and E02212A02S)of the Chinese Academy of Sciencesthe National Natural Science Foundation of China(NSFC,Grant No.12173038)and BeiDou navigation system。
文摘Realtime trigger and localization of bursts are the key functions of GECAM,an all-sky gamma-ray monitor launched on 2020 December 10.We developed a multifunctional trigger and localization software operating in the CPU of the GECAM Electronic Box.This onboard software has the following features:high trigger efficiency for real celestial bursts with a suppression of false triggers caused by charged particle bursts and background fluctuation,dedicated localization algorithm optimized for both short and long bursts,and low time latency of the trigger information which is downlinked through the Global Short Message Communication service of the global BeiDou navigation system.This paper provides a detailed description of the design and development of the trigger and localization software system for GECAM.It covers the general design,workflow,the main functions,and the algorithms used in the system.The paper also includes on-ground trigger tests using simulated gamma-ray bursts generated by a dedicated X-ray tube,as well as an overview of the performance for real celestial bursts during its in-orbit operation.
基金supported by the National Natural Science Foundation of China under grant Nos.12393854,12022502 and 12263007by the High-level Talent Support program of Yunnan Province。
文摘With great advance of ground-based extensive air shower arrays,such as LHAASO and HAWC,many very high energy(VHE)gamma-ray sources have been discovered and are being monitored regardless of the day and the night.Hence,the Sun and Moon would have some impacts on the observation of gamma-ray sources,which have not been taken into account in previous analysis.In this paper,the influence of the Sun and Moon on the observation of very high energy gamma-ray sources when they are near the line of sight of the Sun or Moon is estimated.The tracks of all the known VHE sources are scanned and several VHE sources are found to be very close to the line of sight of the Sun or Moon during some period.The absorption of very high energy gamma rays by sunlight is estimated with detailed method and some useful conclusions are achieved.The main influence is the block of the Sun and Moon on gamma rays and the shadow on the cosmic ray background.The influence is investigated considering the detector angular resolution and some strategies on data analysis are proposed to avoid the underestimation of the gamma-ray emission.
基金supported by the National Key R&D Program of China(No.2022YFA1602901)the local Science and Technology innovation projects of the central government(No.XZ202301YD0037C)the National Natural Science Foundation of China(NSFC,grant No.11933011)。
文摘The initial condition of high-mass star formation is a complex area of study because of the high densities(n_(H_(2))>106cm^(-3))and low temperatures(T_(dust)<18 K)involved.Under such conditions,many molecules become depleted from the gas phase by freezing out onto dust grains.However,the N-bearing and deuterated species could remain gaseous under these extreme conditions,suggesting that they may serve as ideal tracers.In this paper,using the Plateau de Bure Interferometer and Very Large Array observations at 1.3 mm,3.5 mm,and 1.3 cm,we investigate the possible habitats for NH_(3),NH_(2)D,H^(13)CN,HC^(15)N,SO,and C^(18)O in eight massive precluster and protocluster clumps G18.17,G18.21,G23.97N,G23.98,G23.44,G23.97S,G25.38,and G25.71.We found that the NH3cores are in good agreement with the 3.5 mm peak emission,but the NH_(3)is much more extended than the 3.5 mm emission structure.The SO distributions agree well with the 3.5 mm peaks for the evolved star formation stage,but we did not detect any SO emission in the four earliest star formation sources.C^(18)O is a poor tracer in conditions of the cold(■18 K)and dense(■10^(4)cm^(-3))cores,e.g.,the prestellar cores.We also found that the NH_(2)D cores are mainly located in the temperature range of 13.0-20.0 K,and the NH_(2)D lines may be strongly depleted above 20 K.
