We achieved an ultra-flat broad spectrum output with a 20-dB bandwidth of 77.85 nm in a double-clad Yb-doped fiber laser.The intensity difference between the highest and lowest points of the spectrum indicates a flatn...We achieved an ultra-flat broad spectrum output with a 20-dB bandwidth of 77.85 nm in a double-clad Yb-doped fiber laser.The intensity difference between the highest and lowest points of the spectrum indicates a flatness better than4 dB.More notably,this ultra-flat broad spectrum maintains a stable single-pulse mode-locking state.With the increase of pump power,an ultra-wide spectrum with a 20-dB bandwidth approaching 100 nm was formed at a pump power of 2.25 W.Additionally,we obtained a 9-pulse mode-locked state at another PC station with the same pump,which is the highest number of stable mode-locked pulse bursts observed so far with a first-order Raman frequency shift.This fiber laser shows its benefits of ultra-flat broad spectrum,high stability,and ease of fabrication,which provides a new method of obtaining the broadband light source for multiple practical applications.展开更多
The telescopes and the infrastructures may alter the local wind environment around the observatory and further affect the observing environment.After the completion of site testing,it is necessary to analyze the wind ...The telescopes and the infrastructures may alter the local wind environment around the observatory and further affect the observing environment.After the completion of site testing,it is necessary to analyze the wind environment of the entire site and plan the telescope layout to make use of the excellent conditions scientifically and rationally.Taking a typical observatory as an example,the effect of topographical features on the wind environment and the mutual interference between telescope enclosures are analyzed by using the Computational Fluid Dynamics(CFD)method.The CFD simulations are compared with the seeing data from the Differential Image Motion Monitor,and the results are in good agreement,which verifies the effectiveness of the CFD method.The results of wind environment analysis can provide reasonable suggestions for site layout and construction,reducing the interference effects and improving the observing environment.展开更多
For the laboratory astrophysics community, those spectroscopic modeling codes extensively used in astronomy, e.g. Chianti, AtomDB, Cloudy and Xstar, cannot be directly applied to analyzing laboratory measurements due ...For the laboratory astrophysics community, those spectroscopic modeling codes extensively used in astronomy, e.g. Chianti, AtomDB, Cloudy and Xstar, cannot be directly applied to analyzing laboratory measurements due to their discrepancies from astrophysical cases. For example, plasma from an electron beam ion trap has an electron energy distribution that follows a Gaussian profile, instead of a Maxwellian one. The laboratory miniature for a compact object produced by a laser-driven implo- sion shows a departure from equilibrium, that often occurs in celestial objects, so we setup a spectral analysis system for astrophysical and laboratory （SASAL） plasmas to act as a bridge between them, which benefits the laboratory astrophysical community.展开更多
Using the 1.26 m National Astronomical Observatory-Guangzhou University Infrared/Optical Telescope(NGT),we monitor one BL Lac object,OJ 287.For this source,we obtain 15094 gri observations(4900 at g band,5184 at r ban...Using the 1.26 m National Astronomical Observatory-Guangzhou University Infrared/Optical Telescope(NGT),we monitor one BL Lac object,OJ 287.For this source,we obtain 15094 gri observations(4900 at g band,5184 at r band and 5010 at i band)in 155 nights from 2014 December 13 to 2019 March15.Based on the upper observations,we obtain the following results.(1)The total variation amplitude is~2.3 mag.(2)There are intra-day variabilities(IDVs).The IDV timescales(△T)are in the range from 7.69 min(Δm=0.06±0.02 mag)to 371.09 min(Δm=0.26±0.04 mag).(3)There are strong correlations betweenΔT andΔm,△m=(2.91±0.66)×10^(-4)ΔT+(0.08±0.009),with r=0.52,p=5.33×10^(-5).(4)There are intra-day periods in this source,with the period P≈94 min on 2017 December 10.When we supplement the observations from the literature,we can obtain that the long-term period is about 12.02±0.41 yr.(5)The spectral properties of OJ 287 show the bluer-when-brighter behavior,whatever state the source is at.展开更多
We report B, V and R band CCD photometry of the Seyfert galaxy NGC 4151 obtained with the 1.0m telescope at Weihai Observatory of Shandong University and the 1.56 m telescope at Shanghai Astronomical Observatory from ...We report B, V and R band CCD photometry of the Seyfert galaxy NGC 4151 obtained with the 1.0m telescope at Weihai Observatory of Shandong University and the 1.56 m telescope at Shanghai Astronomical Observatory from 2005 December to 2013 February. Combining all available data from literature, we have constructed a historical light curve from 1910 to 2013 to study the periodicity of the source using three different methods （the Jurkevich method, the Lomb-Scargle periodogram method and the Discrete Correlation Function method）. We find possible periods of P1 = 4 ± 0.1,/92 = 7.5 ±0.3 and P3 = 15.9± 0.3 yr.展开更多
Abstract The optical observations of the type Ic supernova （SN lc） SN 2012ap in NGC 1729 are presented. A comparison with other SNe Ic indicates that SN 2012ap is highly reddened （with E（B - V）host-0.8 mag） and ...Abstract The optical observations of the type Ic supernova （SN lc） SN 2012ap in NGC 1729 are presented. A comparison with other SNe Ic indicates that SN 2012ap is highly reddened （with E（B - V）host-0.8 mag） and may represent one of the most luminous SNe Ic ever observed, with an absolute V-band peak magnitude of - 19.3±0.5 mag after extinction correction. The near-maximum-light spectrum shows wide spectral features that are typical of broad-lined SNe Ic. One interesting feature in the spectrum is the appearance of some narrow absorption features that can be at- tributed to the diffuse interstellar bands, consistent with the large reddening inferred from the photometric method. Based on the light curves and the spectral data, we esti- mate that SN 2012ap produced a 56Ni mass of - 0.3 -b 0.1M in the explosion, with an ejecta mass of 2.4^＋0.7 -0.7M and a kinetic energy of EK=1.1^＋0.4 -0.4×10^52 erg. The properties of its progenitor are also briefly discussed.展开更多
The impact of structural stiffness on optical axis deviation poses a significant challenge in the design of equatorial telescope structures.A comprehensive analysis during the design process can reduce the reliance of...The impact of structural stiffness on optical axis deviation poses a significant challenge in the design of equatorial telescope structures.A comprehensive analysis during the design process can reduce the reliance of a telescope on advanced control technologies,thereby improving its economic feasibility.Although full-system finite element analyses are reliable,they are encumbered by significant time requirements and limitations in covering all possible telescope orientations.Therefore,we propose an efficient and comprehensive analytical method to evaluate the optical axis deviation of equatorial telescopes across a full range of angles.To address the challenge of ensuring that the analysis covers all possible positions of an equatorial telescope,based on a model from SiTian project,we analyze the optical axis deviations caused by the fork arm at 25 different angles and then use fitting methods to obtain results for all angles.Based on the analysis results of the optical axis deviation caused by the stiffness of the optical tube in the horizontal position,we derive the results for the tube at any position using geometric relationships.Finally,we calculate the coupling factors and combine these impacts.Furthermore,we identify six discrete feature points to reflect possible telescope orientations and conduct comprehensive finite element analyses.The results are in alignment with those acquired through a comprehensive computational approach.展开更多
We study the dimensionless spin parameter j ≡ cJ/（GM2） of different kinds of uniformly rotating compact stars, including traditional neutron stars, hyperonic neutron stars and hybrid stars, based on relativistic me...We study the dimensionless spin parameter j ≡ cJ/（GM2） of different kinds of uniformly rotating compact stars, including traditional neutron stars, hyperonic neutron stars and hybrid stars, based on relativistic mean field theory and the MIT bag model. It is found that j ~ 0.7, which had been suggested in traditional neutron stars, is sustained for hyperonic neutron stars and hybrid stars with M 〉 0.5 MG. Not the interior but rather the crust structure of the stars is a key factor to determine jmax for three kinds of selected compact stars. Furthermore, a universal formula j = 0.63（f/fK） -- 0.42（f/fK）2 ＋ 0.48（f/fK）z is suggested to determine the spin parameter at any rotational frequency f smaller than the Keplerian frequency fK.展开更多
A counter-streaming flow system is a test-bed to investigate the astrophysical collisionless shock（CS） formation in the laboratory. Electrostatic/electromagnetic instabilities, competitively growing in the system an...A counter-streaming flow system is a test-bed to investigate the astrophysical collisionless shock（CS） formation in the laboratory. Electrostatic/electromagnetic instabilities, competitively growing in the system and exciting the CS formation, are sensitive to the flows parameters. One of the most important parameters is the velocity, determining what kind of instability contributes to the shock formation. Here we successfully measure the evolution of the counter-streaming flows within one shot using a multi-pulses imaging diagnostic technique. With the technique, the average velocity of the high-density-part（ne ≥ 8–9 × 10^19cm^-3） of the flow is directly measured to be of ～ 10^6cm/s between 7 ns and 17 ns.Meanwhile, the average velocity of the low-density-part（ne ≤ 2 × 10^19cm^-3） can be estimated as ～ 10^7cm/s. The experimental results show that a collisionless shock is formed during the low-density-part of the flow interacting with each other.展开更多
The Spectral Imaging Corona Graph(SICG) serves as the optical observation equipment of E-corona in the Chinese Meridian Project Phase II, which aims at monitoring the initial source of solar activities. For the purpos...The Spectral Imaging Corona Graph(SICG) serves as the optical observation equipment of E-corona in the Chinese Meridian Project Phase II, which aims at monitoring the initial source of solar activities. For the purpose of indepth exploration and space weather forecast in the full chain of Sun–Earth space, SICG is designed to work at two wavelengths of 637.4 and 530.3 nm in the quasi-simultaneous observation mode. Thus, the photometric calibration is more challenging to guarantee accurate scientific data of SICG. Two solar photometers are specially developed to match the observing wavelengths and make the photoelectronic conversion traceable. Correspondingly, the calibration process selects the solar disk center as the brightness reference, which compensates for the photometric losses along the atmospheric transmission path. This study derives the calibration coefficients from the two photometers for the E-coronal brightness processing in real time. By modeling aerosol absorption and scattering and comparing with continuous flat-field observation, the photometric calibration of SICG is evaluated with deviations of 2.1% and 2.3% at 637.4 nm and 530.3 nm, respectively. Based on this, the evolution speed of a multitemperature coronal loop was analyzed, facilitating further research into the physical mechanisms of coronal mass ejections.展开更多
In our previous work,we identified~100,000 metal-poor stars([Fe/H]<-1.0)from the LAMOST Survey.This work estimates their chemical abundances and explores the origin and evolution of the Galactic metal-poor disk.Our...In our previous work,we identified~100,000 metal-poor stars([Fe/H]<-1.0)from the LAMOST Survey.This work estimates their chemical abundances and explores the origin and evolution of the Galactic metal-poor disk.Our chemo-dynamical analysis reveals four main populations within the metal-poor disk:(1)a primordial disk older than 12 Gyr with[Fe/H]>-1.5;(2)debris stars from the progenitor galaxy of Gaia±Sausage±Enceladus(GSE),but now residing in the Galactic disk;(3)the metal-poor tail of the metal-rich,high-αdisk formed10±12 Gyr ago,with metallicity lower limit extending to-2.0;(4)the metal-poor tail of the metal-rich,low-αdisk younger than 8 Gyr,reaching a lower metallicity limit of-1.8.These results reveal the presence of a primordial disk and show that both high-αand low-αdisks reach lower metallicities than previously thought.Analysis of merger debris reveals that Wukong,with extremely low metallicity,likely originates from merger events distinct from GSE.Additionally,three new substructures are identified:ShangGu-1,characterized by unusual[Fe/H]-eccentricity correlations;ShangGu-2,possibly heated disk stars;and ShangGu-3,which can be divided into four subgroups based on differing orbital directions,with two aligning with the previously known Nyx and Nyx-2.展开更多
The dust-scattered stray light in an inner-occulted coronagraph mainly arises from dust particles on the surfaces of the objective lens.Due to the random accumulation of dust on the lens surfaces,it is challenging to ...The dust-scattered stray light in an inner-occulted coronagraph mainly arises from dust particles on the surfaces of the objective lens.Due to the random accumulation of dust on the lens surfaces,it is challenging to monitor this type of stray light and no application can be used for its real-time monitor in the past.In this study,we provide a system and method to overcome this issue,and these have been applied to the Spectral Imaging CoronaGraph(SICG)of the Chinese Meridian Project.The method is based on the relation between the sizes of dust particles and its stray light level at the imaging plane established in the laboratory and the relation between the real size of dust particles and the occupancies on the imaging plane.To monitor the stray light levels accounted for by dusts,one needs only an image of the objective lens that can be provided by the auxiliary imaging system that specially comes with SICG.Our tests show that the errors of the method are less or about 2%,giving a strong confidence in its accuracy.It provides a handy tool to monitor the dust level of the objective lens of SICG and has significantly improved the efficiency of the pipeline of stray light control.展开更多
Changing-look(CL)active galactic nuclei(AGNs)are an extremely rare type of AGNs,characterized by the appearance(turn-on)or disappearance(turn-off)of broad emission lines within months to years.We construct a sample of...Changing-look(CL)active galactic nuclei(AGNs)are an extremely rare type of AGNs,characterized by the appearance(turn-on)or disappearance(turn-off)of broad emission lines within months to years.We construct a sample of 211 CL AGN candidates by systematically searching the Sloan Digital Sky Survey spectra classified as GALAXY,but with the Zwicky Transient Facility and Near-Earth Object Wide-Field Infrared Explorer midinfrared light curves showing significant variability,at the redshift range from 0.1 to 0.75.To examine the success rate of this method,we cross-match the candidate sample with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope and the Dark Energy Spectroscopic Instrument for repeat spectra,finding that the success rate of this method is 50%.By incorporating previously reported CL AGNs,a total of 48 CL AGNs have been identified within our sample,including two recurrent CL AGNs newly confirmed in this work.Our results suggest that the typical rest-frame timescale of CL behavior is from 1.7 to 18.1 yr,which is inconsistent with the obscuration model,and the Eddington ratios of CL AGNs are about 0.01 in the bright state.Additionally,our CL AGN sample follows the M_(BH)–σ_(*)relation of quiescent galaxies.In the future,we expect to detect more galaxies turning into Type 1 AGNs in this CL AGN candidate sample.展开更多
In this study, we provide a detailed case study of the X-pattern of equatorial ionization anomaly(EIA) observed on the night of September 12, 2021 by the Global-scale Observations of the Limb and Disk(GOLD) mission. U...In this study, we provide a detailed case study of the X-pattern of equatorial ionization anomaly(EIA) observed on the night of September 12, 2021 by the Global-scale Observations of the Limb and Disk(GOLD) mission. Unlike most previous studies about the X-pattern observed under the severely disturbed background ionosphere, this event is observed under geomagnetically quiet and low solar activity conditions. GOLD's continuous observations reveal that the X-pattern intensity evolves with local time, while its center's longitude remains constant. The total electron content(TEC) data derived from the ground-based Global Navigation Satellite System(GNSS) network aligns well with GOLD observations in capturing the formation of the X-pattern, extending coverage to areas beyond GOLD's observational reach. Additionally, the ESA's Swarm mission show that both sides of the X-pattern can coincide with the occurrence of small-scale equatorial plasma bubbles(EPBs). To further analyze the possible drivers of the X-pattern, observations from the Ionospheric Connection Explorer(ICON) satellite were used. It shows that the latitudinal expansion(or width) between the EIA crests in two hemispheres is proportional(or inversely proportional) to the upward(or downward) plasma drift velocity, which suggests that the zonal electric field should have a notable influence on the formation of EIA X-pattern. Further simulations using the SAMI2 model support this mechanism, as the X-pattern of EIA is successfully reproduced by setting the vertical plasma drift to different values at different longitudes.展开更多
The Van Allen radiation belts are doughnut-shaped zones surrounding Earth, filled with highly energetic charged particles whose sources or loss mechanisms have been investigated for decades. As for the inner belt, cos...The Van Allen radiation belts are doughnut-shaped zones surrounding Earth, filled with highly energetic charged particles whose sources or loss mechanisms have been investigated for decades. As for the inner belt, cosmic ray albedo neutron decay(CRAND),radial diffusion, and local acceleration have been considered principal sources of electrons, whereas protons are predominantly from CRAND and solar protons. In this article, lightning-induced neutrons from Earth's upper atmosphere are suggested as a possible source of protons and electrons in the inner radiation belt. These terrestrial neutrons can contribute to the inner belt population by undergoing nuclear decay. Several approaches are proposed and discussed to evaluate the potential contribution of lightning-induced neutrons to the inner belt, including magnitude estimation, Monte Carlo simulations, and in situ observations. This article discusses some avenues of further study to determine the contribution of lightning-induced neutrons to the inner radiation belt.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
This paper presents a comprehensive analysis of the photometric system of the University of Chinese Academy of Sciences 70 cm Telescope located at the Yan-qi Lake campus of the University of Chinese Academy of Science...This paper presents a comprehensive analysis of the photometric system of the University of Chinese Academy of Sciences 70 cm Telescope located at the Yan-qi Lake campus of the University of Chinese Academy of Sciences.We evaluated the linearity,bias stability,and dark current of the camera.Utilizing the Johnson-Cousins Blue-Visible-Red-Infrared filter system and an Andor DZ936 charge-coupled device camera,we conducted extensive observations of Landolt standard stars to determine the color terms,atmospheric extinction coefficients,photometric zero-points,and the sky background brightness.The results indicate that this telescope demonstrates excellent performance in photometric calibration and good system performance overall,meeting the requirements for limited scientific research and teaching purposes.展开更多
Recent observations have demonstrated the capability of mapping the solar coronal magnetic field using the technique of coronal seismology based on the ubiquitous propagating Alfvénic/kink waves through imaging s...Recent observations have demonstrated the capability of mapping the solar coronal magnetic field using the technique of coronal seismology based on the ubiquitous propagating Alfvénic/kink waves through imaging spectroscopy.We established a magnetohydrodynamic model of a gravitationally stratified open magnetic flux tube,exciting kink waves propagating upwards along the tube.Forward modeling was performed to synthesize the Fe XIII 1074.7 and 1079.8 nm spectral line profiles,which were then used to determine the wave phase speed,plasma density,and magnetic field with seismology method.A comparison between the seismologically inferred results and the corresponding input values verifies the reliability of the seismology method.In addition,we also identified some factors that could lead to errors during magnetic field measurements.Our results may serve as a valuable reference for current and future coronal magnetic field measurements based on observations of propagating kink waves.展开更多
The role of galaxy morphology and stellar population properties in galaxy evolution is crucial for understanding the transition from star-forming to quiescent galaxies.We present an analysis of 94 galaxies with Hδabs...The role of galaxy morphology and stellar population properties in galaxy evolution is crucial for understanding the transition from star-forming to quiescent galaxies.We present an analysis of 94 galaxies with Hδabsorption line equivalent widths greater than 2?,selected from the DEEP2 survey EGS field(0<z<1).The wealth of multi-wavelength coverage enables accurate stellar mass measurements from SED fitting,SFR measurements from UV and MIR,and galaxy population classification based on the UVJ diagram.Using HST F814W images,we performed a morphological analysis and found that most galaxies exhibit disk-like structures,with some showing bulge-dominated profiles.The size of our sample is roughly in between the star-forming and quiescent galaxies,implying a transition of galaxy population.We also examined the role of central stellar density(Σ1)in galaxy evolution and found that galaxies with higherΣ1tend to evolve into quiescent galaxies earlier,supporting the“downsizing”scenario.These findings underscore the importance of size,mass,and central density in galaxy evolution.展开更多
As part of the LAMOST medium-resolution spectroscopic survey,the LAMOST-MRS-O is a non-time domain survey that aims to perform medium-resolution spectral observations for member stars in the open cluster areas.This su...As part of the LAMOST medium-resolution spectroscopic survey,the LAMOST-MRS-O is a non-time domain survey that aims to perform medium-resolution spectral observations for member stars in the open cluster areas.This survey plans to obtain the spectroscopic parameters such as radial velocity and metal abundances of member stars and provide data support for further study on the chemical and dynamical characteristics and evolution of open clusters in combination with Gaia data.We have completed the observations on ten open cluster fields and obtained 235184 medium-resolution spectra of 133792 stars.Based on the data analyzed of LAMOST DR11v1.1,for some clusters of particular concern,it is found that the sampling ratio of members stars with Gmag<15 mag can reach 70%,which indicates that the LAMOST-MRS-O has reached our initial design goal.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.12204132)the Natural Science Foundation of Shandong Province,China(Grant No.ZR2021MF122)+1 种基金Shandong Province TechnologyBased SME Innovation Enhancement Project(Grant No.2024TSGC0715)the Postgraduate Education Reform Project of Shandong Province,China(Grant No.SDYJSJGC2024107)。
文摘We achieved an ultra-flat broad spectrum output with a 20-dB bandwidth of 77.85 nm in a double-clad Yb-doped fiber laser.The intensity difference between the highest and lowest points of the spectrum indicates a flatness better than4 dB.More notably,this ultra-flat broad spectrum maintains a stable single-pulse mode-locking state.With the increase of pump power,an ultra-wide spectrum with a 20-dB bandwidth approaching 100 nm was formed at a pump power of 2.25 W.Additionally,we obtained a 9-pulse mode-locked state at another PC station with the same pump,which is the highest number of stable mode-locked pulse bursts observed so far with a first-order Raman frequency shift.This fiber laser shows its benefits of ultra-flat broad spectrum,high stability,and ease of fabrication,which provides a new method of obtaining the broadband light source for multiple practical applications.
基金supported by the National Natural Science Foundation of China(U1831209)。
文摘The telescopes and the infrastructures may alter the local wind environment around the observatory and further affect the observing environment.After the completion of site testing,it is necessary to analyze the wind environment of the entire site and plan the telescope layout to make use of the excellent conditions scientifically and rationally.Taking a typical observatory as an example,the effect of topographical features on the wind environment and the mutual interference between telescope enclosures are analyzed by using the Computational Fluid Dynamics(CFD)method.The CFD simulations are compared with the seeing data from the Differential Image Motion Monitor,and the results are in good agreement,which verifies the effectiveness of the CFD method.The results of wind environment analysis can provide reasonable suggestions for site layout and construction,reducing the interference effects and improving the observing environment.
基金Supported by the National Natural Science Foundation of China
文摘For the laboratory astrophysics community, those spectroscopic modeling codes extensively used in astronomy, e.g. Chianti, AtomDB, Cloudy and Xstar, cannot be directly applied to analyzing laboratory measurements due to their discrepancies from astrophysical cases. For example, plasma from an electron beam ion trap has an electron energy distribution that follows a Gaussian profile, instead of a Maxwellian one. The laboratory miniature for a compact object produced by a laser-driven implo- sion shows a departure from equilibrium, that often occurs in celestial objects, so we setup a spectral analysis system for astrophysical and laboratory （SASAL） plasmas to act as a bridge between them, which benefits the laboratory astrophysical community.
基金partially supported by the National Natural Science Foundation of China(Grant Nos.U1831119,U1531245,U1431112,11733006,11503004 and 11403006)Science and Technology Program of Guangzhou(201707010401)。
文摘Using the 1.26 m National Astronomical Observatory-Guangzhou University Infrared/Optical Telescope(NGT),we monitor one BL Lac object,OJ 287.For this source,we obtain 15094 gri observations(4900 at g band,5184 at r band and 5010 at i band)in 155 nights from 2014 December 13 to 2019 March15.Based on the upper observations,we obtain the following results.(1)The total variation amplitude is~2.3 mag.(2)There are intra-day variabilities(IDVs).The IDV timescales(△T)are in the range from 7.69 min(Δm=0.06±0.02 mag)to 371.09 min(Δm=0.26±0.04 mag).(3)There are strong correlations betweenΔT andΔm,△m=(2.91±0.66)×10^(-4)ΔT+(0.08±0.009),with r=0.52,p=5.33×10^(-5).(4)There are intra-day periods in this source,with the period P≈94 min on 2017 December 10.When we supplement the observations from the literature,we can obtain that the long-term period is about 12.02±0.41 yr.(5)The spectral properties of OJ 287 show the bluer-when-brighter behavior,whatever state the source is at.
基金supported by the National Natural Science Foundation of China (Nos.11203016,11143012,10778619,10778701 and 10903005)the Natural Science Foundation of Shandong Province (No.ZR2012AQ008)
文摘We report B, V and R band CCD photometry of the Seyfert galaxy NGC 4151 obtained with the 1.0m telescope at Weihai Observatory of Shandong University and the 1.56 m telescope at Shanghai Astronomical Observatory from 2005 December to 2013 February. Combining all available data from literature, we have constructed a historical light curve from 1910 to 2013 to study the periodicity of the source using three different methods （the Jurkevich method, the Lomb-Scargle periodogram method and the Discrete Correlation Function method）. We find possible periods of P1 = 4 ± 0.1,/92 = 7.5 ±0.3 and P3 = 15.9± 0.3 yr.
基金Supported by the National Natural Science Foundation of China
文摘Abstract The optical observations of the type Ic supernova （SN lc） SN 2012ap in NGC 1729 are presented. A comparison with other SNe Ic indicates that SN 2012ap is highly reddened （with E（B - V）host-0.8 mag） and may represent one of the most luminous SNe Ic ever observed, with an absolute V-band peak magnitude of - 19.3±0.5 mag after extinction correction. The near-maximum-light spectrum shows wide spectral features that are typical of broad-lined SNe Ic. One interesting feature in the spectrum is the appearance of some narrow absorption features that can be at- tributed to the diffuse interstellar bands, consistent with the large reddening inferred from the photometric method. Based on the light curves and the spectral data, we esti- mate that SN 2012ap produced a 56Ni mass of - 0.3 -b 0.1M in the explosion, with an ejecta mass of 2.4^＋0.7 -0.7M and a kinetic energy of EK=1.1^＋0.4 -0.4×10^52 erg. The properties of its progenitor are also briefly discussed.
文摘The impact of structural stiffness on optical axis deviation poses a significant challenge in the design of equatorial telescope structures.A comprehensive analysis during the design process can reduce the reliance of a telescope on advanced control technologies,thereby improving its economic feasibility.Although full-system finite element analyses are reliable,they are encumbered by significant time requirements and limitations in covering all possible telescope orientations.Therefore,we propose an efficient and comprehensive analytical method to evaluate the optical axis deviation of equatorial telescopes across a full range of angles.To address the challenge of ensuring that the analysis covers all possible positions of an equatorial telescope,based on a model from SiTian project,we analyze the optical axis deviations caused by the fork arm at 25 different angles and then use fitting methods to obtain results for all angles.Based on the analysis results of the optical axis deviation caused by the stiffness of the optical tube in the horizontal position,we derive the results for the tube at any position using geometric relationships.Finally,we calculate the coupling factors and combine these impacts.Furthermore,we identify six discrete feature points to reflect possible telescope orientations and conduct comprehensive finite element analyses.The results are in alignment with those acquired through a comprehensive computational approach.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11175108, U1432119, 1146114100, 11205075, 11375076 and 11475104)the Shandong Natural Science Foundation (Grant No. ZR2014AQ012)the Young Scholars Program of Shandong University, Weihai (Grant No. 2015WHWLJH01)
文摘We study the dimensionless spin parameter j ≡ cJ/（GM2） of different kinds of uniformly rotating compact stars, including traditional neutron stars, hyperonic neutron stars and hybrid stars, based on relativistic mean field theory and the MIT bag model. It is found that j ~ 0.7, which had been suggested in traditional neutron stars, is sustained for hyperonic neutron stars and hybrid stars with M 〉 0.5 MG. Not the interior but rather the crust structure of the stars is a key factor to determine jmax for three kinds of selected compact stars. Furthermore, a universal formula j = 0.63（f/fK） -- 0.42（f/fK）2 ＋ 0.48（f/fK）z is suggested to determine the spin parameter at any rotational frequency f smaller than the Keplerian frequency fK.
基金Project supported by the National Basic Research Program of China(Grant No.2013 CBA01501/3)the National Natural Science Foundation of China(Grant Nos.11503041,11135012,11375262,11573040,11574390,and 11220101002)China Postdoctoral Science Foundation(Grant No.2015M571124)
文摘A counter-streaming flow system is a test-bed to investigate the astrophysical collisionless shock（CS） formation in the laboratory. Electrostatic/electromagnetic instabilities, competitively growing in the system and exciting the CS formation, are sensitive to the flows parameters. One of the most important parameters is the velocity, determining what kind of instability contributes to the shock formation. Here we successfully measure the evolution of the counter-streaming flows within one shot using a multi-pulses imaging diagnostic technique. With the technique, the average velocity of the high-density-part（ne ≥ 8–9 × 10^19cm^-3） of the flow is directly measured to be of ～ 10^6cm/s between 7 ns and 17 ns.Meanwhile, the average velocity of the low-density-part（ne ≤ 2 × 10^19cm^-3） can be estimated as ～ 10^7cm/s. The experimental results show that a collisionless shock is formed during the low-density-part of the flow interacting with each other.
基金supported by the Chinese Meridian Project(CMP) and the National Natural Science Foundation of China(grant Nos.42230203,42374220,and 12173086)。
文摘The Spectral Imaging Corona Graph(SICG) serves as the optical observation equipment of E-corona in the Chinese Meridian Project Phase II, which aims at monitoring the initial source of solar activities. For the purpose of indepth exploration and space weather forecast in the full chain of Sun–Earth space, SICG is designed to work at two wavelengths of 637.4 and 530.3 nm in the quasi-simultaneous observation mode. Thus, the photometric calibration is more challenging to guarantee accurate scientific data of SICG. Two solar photometers are specially developed to match the observing wavelengths and make the photoelectronic conversion traceable. Correspondingly, the calibration process selects the solar disk center as the brightness reference, which compensates for the photometric losses along the atmospheric transmission path. This study derives the calibration coefficients from the two photometers for the E-coronal brightness processing in real time. By modeling aerosol absorption and scattering and comparing with continuous flat-field observation, the photometric calibration of SICG is evaluated with deviations of 2.1% and 2.3% at 637.4 nm and 530.3 nm, respectively. Based on this, the evolution speed of a multitemperature coronal loop was analyzed, facilitating further research into the physical mechanisms of coronal mass ejections.
基金supported by the National Natural Science Foundation of China(NSFC,grant Nos.11988101 and12222305)National Key R&D Program of China No.2024YFA1611900Guoshoujing Telescope(the Large Sky Area Multi-Object Fiber Spectroscopic Telescope,LAMOST)is a National Major Scientific Project built by the Chinese Academy of Sciences。
文摘In our previous work,we identified~100,000 metal-poor stars([Fe/H]<-1.0)from the LAMOST Survey.This work estimates their chemical abundances and explores the origin and evolution of the Galactic metal-poor disk.Our chemo-dynamical analysis reveals four main populations within the metal-poor disk:(1)a primordial disk older than 12 Gyr with[Fe/H]>-1.5;(2)debris stars from the progenitor galaxy of Gaia±Sausage±Enceladus(GSE),but now residing in the Galactic disk;(3)the metal-poor tail of the metal-rich,high-αdisk formed10±12 Gyr ago,with metallicity lower limit extending to-2.0;(4)the metal-poor tail of the metal-rich,low-αdisk younger than 8 Gyr,reaching a lower metallicity limit of-1.8.These results reveal the presence of a primordial disk and show that both high-αand low-αdisks reach lower metallicities than previously thought.Analysis of merger debris reveals that Wukong,with extremely low metallicity,likely originates from merger events distinct from GSE.Additionally,three new substructures are identified:ShangGu-1,characterized by unusual[Fe/H]-eccentricity correlations;ShangGu-2,possibly heated disk stars;and ShangGu-3,which can be divided into four subgroups based on differing orbital directions,with two aligning with the previously known Nyx and Nyx-2.
基金supported by National Natural Science Foundation of China(grant Nos.42274227,41904168,U1931122)National Key R&D Program of China No.2021 YFA0718600,and the Chinese Meridian Project(CMP).
文摘The dust-scattered stray light in an inner-occulted coronagraph mainly arises from dust particles on the surfaces of the objective lens.Due to the random accumulation of dust on the lens surfaces,it is challenging to monitor this type of stray light and no application can be used for its real-time monitor in the past.In this study,we provide a system and method to overcome this issue,and these have been applied to the Spectral Imaging CoronaGraph(SICG)of the Chinese Meridian Project.The method is based on the relation between the sizes of dust particles and its stray light level at the imaging plane established in the laboratory and the relation between the real size of dust particles and the occupancies on the imaging plane.To monitor the stray light levels accounted for by dusts,one needs only an image of the objective lens that can be provided by the auxiliary imaging system that specially comes with SICG.Our tests show that the errors of the method are less or about 2%,giving a strong confidence in its accuracy.It provides a handy tool to monitor the dust level of the objective lens of SICG and has significantly improved the efficiency of the pipeline of stray light control.
基金supported by the National Key R&D Program of China with grant No.2023YFA1608100supported by the National Natural Science Foundation of China(NSFC)under grant No.12273013+4 种基金support from the National Key R&D Program of China(grant Nos.2023YFA1607804,2022YFA1602902,and 2023YFA1607800)other NSFC projects(grant Nos.12120101003,12373010,12173051,and 12233008)the China Manned Space Project(No.CMS-CSST-2025-A06)the Strategic Priority Research Program of the Chinese Academy of Sciences with grant Nos.XDB0550100 and XDB0550000supported by the National Science Foundation under grant No.AST-2034437。
文摘Changing-look(CL)active galactic nuclei(AGNs)are an extremely rare type of AGNs,characterized by the appearance(turn-on)or disappearance(turn-off)of broad emission lines within months to years.We construct a sample of 211 CL AGN candidates by systematically searching the Sloan Digital Sky Survey spectra classified as GALAXY,but with the Zwicky Transient Facility and Near-Earth Object Wide-Field Infrared Explorer midinfrared light curves showing significant variability,at the redshift range from 0.1 to 0.75.To examine the success rate of this method,we cross-match the candidate sample with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope and the Dark Energy Spectroscopic Instrument for repeat spectra,finding that the success rate of this method is 50%.By incorporating previously reported CL AGNs,a total of 48 CL AGNs have been identified within our sample,including two recurrent CL AGNs newly confirmed in this work.Our results suggest that the typical rest-frame timescale of CL behavior is from 1.7 to 18.1 yr,which is inconsistent with the obscuration model,and the Eddington ratios of CL AGNs are about 0.01 in the bright state.Additionally,our CL AGN sample follows the M_(BH)–σ_(*)relation of quiescent galaxies.In the future,we expect to detect more galaxies turning into Type 1 AGNs in this CL AGN candidate sample.
基金supported by the National Key R&D Program of China (Grant No. 2022YFF0503700)the special funds of Hubei Luojia Laboratory (220100011)+1 种基金Chao Xiong is supported by the ISSI-BJ project, “the electromagnetic data validation and scientific application research based on CSES satellite”ISSI/ISSI-BJ project “Multi-Scale Magnetosphere–Ionosphere–Thermosphere Interaction”。
文摘In this study, we provide a detailed case study of the X-pattern of equatorial ionization anomaly(EIA) observed on the night of September 12, 2021 by the Global-scale Observations of the Limb and Disk(GOLD) mission. Unlike most previous studies about the X-pattern observed under the severely disturbed background ionosphere, this event is observed under geomagnetically quiet and low solar activity conditions. GOLD's continuous observations reveal that the X-pattern intensity evolves with local time, while its center's longitude remains constant. The total electron content(TEC) data derived from the ground-based Global Navigation Satellite System(GNSS) network aligns well with GOLD observations in capturing the formation of the X-pattern, extending coverage to areas beyond GOLD's observational reach. Additionally, the ESA's Swarm mission show that both sides of the X-pattern can coincide with the occurrence of small-scale equatorial plasma bubbles(EPBs). To further analyze the possible drivers of the X-pattern, observations from the Ionospheric Connection Explorer(ICON) satellite were used. It shows that the latitudinal expansion(or width) between the EIA crests in two hemispheres is proportional(or inversely proportional) to the upward(or downward) plasma drift velocity, which suggests that the zonal electric field should have a notable influence on the formation of EIA X-pattern. Further simulations using the SAMI2 model support this mechanism, as the X-pattern of EIA is successfully reproduced by setting the vertical plasma drift to different values at different longitudes.
基金supported by the National Natural Science Foundation of China (No. 42225405 and No. 42350710200)。
文摘The Van Allen radiation belts are doughnut-shaped zones surrounding Earth, filled with highly energetic charged particles whose sources or loss mechanisms have been investigated for decades. As for the inner belt, cosmic ray albedo neutron decay(CRAND),radial diffusion, and local acceleration have been considered principal sources of electrons, whereas protons are predominantly from CRAND and solar protons. In this article, lightning-induced neutrons from Earth's upper atmosphere are suggested as a possible source of protons and electrons in the inner radiation belt. These terrestrial neutrons can contribute to the inner belt population by undergoing nuclear decay. Several approaches are proposed and discussed to evaluate the potential contribution of lightning-induced neutrons to the inner belt, including magnitude estimation, Monte Carlo simulations, and in situ observations. This article discusses some avenues of further study to determine the contribution of lightning-induced neutrons to the inner radiation belt.
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 National Key R&D Program of China(2023YFA1609700)Research and Education Integration Funding。
文摘This paper presents a comprehensive analysis of the photometric system of the University of Chinese Academy of Sciences 70 cm Telescope located at the Yan-qi Lake campus of the University of Chinese Academy of Sciences.We evaluated the linearity,bias stability,and dark current of the camera.Utilizing the Johnson-Cousins Blue-Visible-Red-Infrared filter system and an Andor DZ936 charge-coupled device camera,we conducted extensive observations of Landolt standard stars to determine the color terms,atmospheric extinction coefficients,photometric zero-points,and the sky background brightness.The results indicate that this telescope demonstrates excellent performance in photometric calibration and good system performance overall,meeting the requirements for limited scientific research and teaching purposes.
基金supported by the National Natural Science Foundation of China (NSFC,grant No.12425301)the Strategic Priority Research Program of the Chinese Academy of Sciences (grant No.XDB0560000)+6 种基金the National Key R&D Program of China No.2022YFF0503800support from the National Natural Science Foundation of China (NSFC,grant No.12203030)supported by the C1 grant TRACEspace of Internal Funds KU Leuven and a Senior Research Project (G088021N) of the FWO Vlaanderensupport from the Flemish Government under the long-term structural Methusalem funding program,project SOUL:Stellar evolution in full glory,grant METH/24/012 at KU Leuvensubsidized by the Belgian Federal Science Policy Office through the contract B2/223/P1/CLOSE-UPfunding under the Horizon Europe program of the European Union under grant agreement (No.101131534)support by an FWO (Fonds voor Wetenschappelijk Onderzoek-Vlaanderen)postdoctoral fellowship (1273221N)
文摘Recent observations have demonstrated the capability of mapping the solar coronal magnetic field using the technique of coronal seismology based on the ubiquitous propagating Alfvénic/kink waves through imaging spectroscopy.We established a magnetohydrodynamic model of a gravitationally stratified open magnetic flux tube,exciting kink waves propagating upwards along the tube.Forward modeling was performed to synthesize the Fe XIII 1074.7 and 1079.8 nm spectral line profiles,which were then used to determine the wave phase speed,plasma density,and magnetic field with seismology method.A comparison between the seismologically inferred results and the corresponding input values verifies the reliability of the seismology method.In addition,we also identified some factors that could lead to errors during magnetic field measurements.Our results may serve as a valuable reference for current and future coronal magnetic field measurements based on observations of propagating kink waves.
基金sponsored by the National Key R&D Program of China for grant No.2022YFA1605300the National Natural Science Foundation of China(NSFC,Grant Nos.11933003,12173045,and 12273051)。
文摘The role of galaxy morphology and stellar population properties in galaxy evolution is crucial for understanding the transition from star-forming to quiescent galaxies.We present an analysis of 94 galaxies with Hδabsorption line equivalent widths greater than 2?,selected from the DEEP2 survey EGS field(0<z<1).The wealth of multi-wavelength coverage enables accurate stellar mass measurements from SED fitting,SFR measurements from UV and MIR,and galaxy population classification based on the UVJ diagram.Using HST F814W images,we performed a morphological analysis and found that most galaxies exhibit disk-like structures,with some showing bulge-dominated profiles.The size of our sample is roughly in between the star-forming and quiescent galaxies,implying a transition of galaxy population.We also examined the role of central stellar density(Σ1)in galaxy evolution and found that galaxies with higherΣ1tend to evolve into quiescent galaxies earlier,supporting the“downsizing”scenario.These findings underscore the importance of size,mass,and central density in galaxy evolution.
基金supported by the National Natural Science Foundation of China(NSFC)through grants 12090040,12090042,and 12073060the National Key R&D Program of China No.2019YFA0405501+2 种基金J.Z.acknowledges the Youth Innovation Promotion Association CASthe Science and Technology Commission of Shanghai Municipality(grant No.22dz1202400)the Program of Shanghai Academic/Technology Research Leader。
文摘As part of the LAMOST medium-resolution spectroscopic survey,the LAMOST-MRS-O is a non-time domain survey that aims to perform medium-resolution spectral observations for member stars in the open cluster areas.This survey plans to obtain the spectroscopic parameters such as radial velocity and metal abundances of member stars and provide data support for further study on the chemical and dynamical characteristics and evolution of open clusters in combination with Gaia data.We have completed the observations on ten open cluster fields and obtained 235184 medium-resolution spectra of 133792 stars.Based on the data analyzed of LAMOST DR11v1.1,for some clusters of particular concern,it is found that the sampling ratio of members stars with Gmag<15 mag can reach 70%,which indicates that the LAMOST-MRS-O has reached our initial design goal.
