It＇s not every day you happen to see a dead wolf, an elephant and a horse just lying around. But then this is no ordinary location. The animals are just some of the weird and wonderful props used at a special effects...It＇s not every day you happen to see a dead wolf, an elephant and a horse just lying around. But then this is no ordinary location. The animals are just some of the weird and wonderful props used at a special effects makeup studio located in the Dachang Movie Town, Dachang Hui Autonomous County in Langfang City. north of China＇s Hebei Province.展开更多
We identify an S-shaped main-jet axis in the Vela core-collapse supernova remnant(CCSNR)that we attribute to a pair of precessing jets,one of the tens of pairs of jets that exploded the progenitor of Vela according to...We identify an S-shaped main-jet axis in the Vela core-collapse supernova remnant(CCSNR)that we attribute to a pair of precessing jets,one of the tens of pairs of jets that exploded the progenitor of Vela according to the jittering jets explosion mechanism(JJEM).A main-jet axis is a symmetry axis across the CCSNR and through the center.We identify the S-shaped main-jet axis by the high abundance of ejecta elements,oxygen,neon,and magnesium.We bring the number of identified pairs of clumps and ears in Vela to seven,two pairs shaped by the pair of precessing jets that formed the main-jet axis.The pairs and the main-jet axis form the point-symmetric wind-rose structure of Vela.The other five pairs of clumps/ears do not have signatures near the center,only on two opposite sides of the CCSNR.We discuss different possible jet-less shaping mechanisms to form such a point-symmetric morphology and dismiss these processes because they cannot explain the point-symmetric morphology of Vela,the S-shaped high ejecta abundance pattern,and the enormous energy required to shape the S-shaped structure.Our findings strongly support the JJEM and further severely challenge the neutrino-driven explosion mechanism.展开更多
This paper outlines the scientific goals and observational strategies of the Mini-SiTian Array.Mounted at Xinglong Observatory,the Mini-SiTian Array consists of three 30 cm telescopes and has been in operation since 2...This paper outlines the scientific goals and observational strategies of the Mini-SiTian Array.Mounted at Xinglong Observatory,the Mini-SiTian Array consists of three 30 cm telescopes and has been in operation since 2022.The large field of view,combined with the capability for multi-band photometric observations,enables the Mini-SiTian Array to perform rapid follow-up observations to identify optical counterparts of gravitational waves,capture the early light curves of tidal disruption events and supernovae,and monitor stellar flares,Be star outbursts,and cataclysmic variable stars,although its limiting magnitude is not very deep.By collaborating with the Xinglong2.16 m telescope and leveraging a real-time image processing pipeline,simultaneous photometric and spectroscopic observations could be performed to reveal their underlying physical mechanisms.The observational and research experience provides critical guidance for the implementation of the full-scale SiTian project in the future.展开更多
With the advancement of astronomical observation technology,people have a deeper understanding of the formation and evolution of galaxies,but many details of our own Milky Way and other external galaxies are still unk...With the advancement of astronomical observation technology,people have a deeper understanding of the formation and evolution of galaxies,but many details of our own Milky Way and other external galaxies are still unknown.Therefore,by studying the formation and orbital transformation mechanism of satellites,planets and stars,the author puts forward a new theory on the formation and evolution of stars and galaxies,thus revealing the hierarchical structure of galaxies and the formation and evolution laws of main sequence stars,red giants,white dwarfs,black dwarfs,supernovae,neutron stars,black holes and quasars.Some special phenomena in the course of star formation and evolution,such as sunspots,flares,fast radio bursts and gamma-ray bursts,have also been revealed.展开更多
For k given graphs H_(1),...,H_(k) with k≥2,the k-color Ramsey number R(H_(1),...,H_(k)) represents the minimum integer N with the following property:if the edges of the complete graph K_(N) are colored with k colors...For k given graphs H_(1),...,H_(k) with k≥2,the k-color Ramsey number R(H_(1),...,H_(k)) represents the minimum integer N with the following property:if the edges of the complete graph K_(N) are colored with k colors,then there exists some i with 1≤i≤k such that K_(N) has a subgraph in color i isomorphic to H_(i).Let C_(m) be a cycle of length m and K_(1,n) a star of order n+1.In this paper,we systematically introduce the latest research progress on star-quadrilateral Ramsey numbers and provide an overview of Ramsey numbers concerning quadrilaterals,including multicolor cases.展开更多
The emission of anomalous X-ray pulsars(AXPs)and soft gamma-ray repeaters(SGRs)is believed to be powered by the dissipation of their strong magnetic fields,which coined the name“magnetar”.By combining timing and ene...The emission of anomalous X-ray pulsars(AXPs)and soft gamma-ray repeaters(SGRs)is believed to be powered by the dissipation of their strong magnetic fields,which coined the name“magnetar”.By combining timing and energy observational results,the magnetar model can be easily appreciated.From a timing perspective,the magnetic field strengths of AXPs and SGRs,which are calculated under the assumption of dipole radiation,are extremely strong.From an energy perspective,the X-ray/soft gamma-ray luminosities of AXPs and SGRs are larger than their rotational energy loss rates(i.e.,L_(x>E_(rot)).It is thus reasonable to assume that the high-energy radiation comes from magnetic energy decay,and the magnetar model has been extensively discussed(or accepted).However,we argue that:(ⅰ)Calculating magnetic fields by assuming that rotational energy loss is dominated by dipole radiation(i.e.,E_(rot)■E_(μ))may be controversial,and we suggest that the energies carried by outflowing particles should also be considered.(ⅱ)The fact that X-ray luminosity is greater than the rotational energy loss rate does not necessarily mean that the emission energy comes from the magnetic field decaying,which requires further observational testing.Furthermore,some observational facts conflict with the“magnetar”model,such as observations of anti-magnetars,high magnetic field pulsars,and radio and X-ray observations of AXPs/SGRs.Therefore,we propose a crusted strange star model as an alternative,which can explain many more observational facts of AXPs/SGRs.展开更多
AR Aur A+B is a close binary of astrophysical interest because dissimilar surface compositions are reported between similar late B-type dwarfs.A new spectroscopic study on this system was carried out based on the dise...AR Aur A+B is a close binary of astrophysical interest because dissimilar surface compositions are reported between similar late B-type dwarfs.A new spectroscopic study on this system was carried out based on the disentangled spectra,in order to determine their atmospheric parameters and elemental abundances.The effective temperature and microturbulence(determined from the equivalent widths of Fe II lines)turned out to be(11,150 K,0.9 km s^(-1))and(10,650 K,0.1 km s^(-1))for A and B,respectively.The chemical abundances of 28 elements were then derived while taking into account the non-LTE effect for Z≤15 elements(Z:atomic number).The following trends were elucidated for[X/H](abundance of X relative to the Sun):(1)Qualitatively,[X/H]shows a rough global tendency to increase with Z,with the gradient steeper for A than for B.(2)However,considerable dispersion is involved for A,since prominently large peculiarities are seen in specific elements reflecting the characteristics of HgMn stars(e.g.,very deficient N,Al,Sc,Ni;markedly overabundant P,Mn).(3)In contrast,the Z-dependence of[X/H]for B tends to be nearly linear with only a small dispersion.These observational facts may serve as a key to understanding the critical condition for the emergence of the chemical anomaly.展开更多
Daytime star images captured by dedicated near-space star sensors are characterized by short exposures,high noise,and low Signal-to-Noise Ratios(SNRs).Such imaging is also affected by atmospheric turbulence,causing op...Daytime star images captured by dedicated near-space star sensors are characterized by short exposures,high noise,and low Signal-to-Noise Ratios(SNRs).Such imaging is also affected by atmospheric turbulence,causing optical phenomena,such as scintillation,distortion,and jitter.This causes difficulty in recording high-precision star images during the daytime.This study proposes an adaptive star point extraction method based on dynamically predicting stars'positions.First,it predicts the approximate position of stars based on the star catalog,sensor attitude,observation time,and other information,improving the extraction accuracy.Second,it employs a regional SNR sorting method that adaptively selects star images with higher SNRs,suppressing the scintillation effect and enhancing the SNR of star images.Third,depending on the star's motion trajectory characteristics on the image plane,it utilizes the centroid smoothing method for extraction,thus overcoming the impact of star drift.Field experiments demonstrate that the proposed method can effectively overcome star scintillation,drift,and irregular imaging caused by atmospheric turbulence,achieving a 100%success rate.Moreover,the extraction accuracy improves by more than 80%compared to traditional adaptive methods,attaining a value of 0.05 pixels(0.5"),thereby meeting the requirements of daytime astronomical attitude determination and positioning.展开更多
In the current paper,we present a study of the spatial distribution of luminous blue variables(LBVs)and various LBV candidates(c LBVs)with respect to OB associations in the galaxy M33.The identification of blue star g...In the current paper,we present a study of the spatial distribution of luminous blue variables(LBVs)and various LBV candidates(c LBVs)with respect to OB associations in the galaxy M33.The identification of blue star groups was based on the LGGS data and was carried out by two clustering algorithms with initial parameters determined during simulations of random stellar fields.We have found that the distribution of distances to the nearest OB association obtained for the LBV/c LBV sample is close to that for massive stars with Minit>20 M⊙and WolfRayet stars.This result is in good agreement with the standard assumption that LBVs represent an intermediate stage in the evolution of the most massive stars.However,some objects from the LBV/cLBV sample,particularly Fe II-emission stars,demonstrated severe isolation compared to other massive stars,which,together with certain features of their spectra,implicitly indicates that the nature of these objects and other LBVs/cLBVs may differ radically.展开更多
We demonstrate by three-dimensional hydrodynamical simulations of energy deposition into the envelope of a red supergiant model the inflation of a Rayleigh–Taylor unstable envelope that forms a compact clumpy circums...We demonstrate by three-dimensional hydrodynamical simulations of energy deposition into the envelope of a red supergiant model the inflation of a Rayleigh–Taylor unstable envelope that forms a compact clumpy circumstellar material(CSM).Our simulations mimic vigorous core activity years to months before a core-collapse supernova(CCSN)explosion that deposits energy to the outer envelope.The fierce core nuclear activity in the pre-CCSN explosion phase might excite waves that propagate to the envelope.The wave energy is dissipated where envelope convection cannot carry the energy.We deposit this energy into a shell in the outer envelope with a power of L_(wave)=2.6×10^(6)L■or L_(wave)=5.2×10^(5)L■for 0.32 yr.The energy-deposition shell expands while its pressure is higher than its surroundings,but its density is lower.Therefore,this expansion is Rayleigh–Taylor unstable and develops instability fingers.Most of the inflated envelope does not reach the escape velocity in the year of simulation but forms a compact and clumpy CSM.The high density of the inflated envelope implies that if a companion is present in that zone,it will accrete mass at a very high rate and power a pre-explosion outburst.展开更多
Despite many attempts,the origin of UV emission line and continuum in contact binary stars remains unclear.We present a substantial UV spectroscopic analysis of VW Cephei,a late-type contact binary system,using 46 low...Despite many attempts,the origin of UV emission line and continuum in contact binary stars remains unclear.We present a substantial UV spectroscopic analysis of VW Cephei,a late-type contact binary system,using 46 lowresolution spectra from the International Ultraviolet Explorer in the wavelength range 1150-1978À.By modeling continuum and emissions lines in individual spectra,we report the significant detection of O Ⅲ](1660 and 1666À)and Si Ⅳ(1393 and 1402À)line complexes.We observe that UV fluxes for both continuum and emission lines like C Ⅳ,O Ⅲ],C Ⅱ and Si Ⅳ vary significantly(fractional rms variability up to 45%)from hours to years.In addition,line widths also change by hundreds of km s^(-1).The UV flux variabilities observed in the continuum bands and line emissions are uncorrelated.However,most of the flux values follow the binary orbital period observed from optical data.Our analysis indicates that,while the variation in continuum flux may be attributed to a heated photosphere,the line width measurements indicate that the emission lines are likely formed in the dynamical clouds associated with Roche lobe overflow.We estimate the mass transfer rate of M=(0.82±0.01)×10^(-7)M_(⊙)yr^(-1)from UV line fluxes,which is in good agreement with optical studies.展开更多
文摘It＇s not every day you happen to see a dead wolf, an elephant and a horse just lying around. But then this is no ordinary location. The animals are just some of the weird and wonderful props used at a special effects makeup studio located in the Dachang Movie Town, Dachang Hui Autonomous County in Langfang City. north of China＇s Hebei Province.
基金A grant from the Pazy Foundation supported this research
文摘We identify an S-shaped main-jet axis in the Vela core-collapse supernova remnant(CCSNR)that we attribute to a pair of precessing jets,one of the tens of pairs of jets that exploded the progenitor of Vela according to the jittering jets explosion mechanism(JJEM).A main-jet axis is a symmetry axis across the CCSNR and through the center.We identify the S-shaped main-jet axis by the high abundance of ejecta elements,oxygen,neon,and magnesium.We bring the number of identified pairs of clumps and ears in Vela to seven,two pairs shaped by the pair of precessing jets that formed the main-jet axis.The pairs and the main-jet axis form the point-symmetric wind-rose structure of Vela.The other five pairs of clumps/ears do not have signatures near the center,only on two opposite sides of the CCSNR.We discuss different possible jet-less shaping mechanisms to form such a point-symmetric morphology and dismiss these processes because they cannot explain the point-symmetric morphology of Vela,the S-shaped high ejecta abundance pattern,and the enormous energy required to shape the S-shaped structure.Our findings strongly support the JJEM and further severely challenge the neutrino-driven explosion mechanism.
基金supported by the National Key Basic R&D Program of China via 2023YFA1608303the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB0550103)+3 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(grant Nos.XDB0550000,XDB0550100 and XDB0550102)supported from the Strategic Pioneer Program of the Astronomy Large-Scale Scientific Facility,Chinese Academy of Sciences and the Science and Education Integration Funding of University of Chinese Academy of Sciencessupported by the National Natural Science Foundation of China(NSFCgrant Nos.12090040,12090041,12090041,12422303,12261141690,and 12403022)。
文摘This paper outlines the scientific goals and observational strategies of the Mini-SiTian Array.Mounted at Xinglong Observatory,the Mini-SiTian Array consists of three 30 cm telescopes and has been in operation since 2022.The large field of view,combined with the capability for multi-band photometric observations,enables the Mini-SiTian Array to perform rapid follow-up observations to identify optical counterparts of gravitational waves,capture the early light curves of tidal disruption events and supernovae,and monitor stellar flares,Be star outbursts,and cataclysmic variable stars,although its limiting magnitude is not very deep.By collaborating with the Xinglong2.16 m telescope and leveraging a real-time image processing pipeline,simultaneous photometric and spectroscopic observations could be performed to reveal their underlying physical mechanisms.The observational and research experience provides critical guidance for the implementation of the full-scale SiTian project in the future.
文摘With the advancement of astronomical observation technology,people have a deeper understanding of the formation and evolution of galaxies,but many details of our own Milky Way and other external galaxies are still unknown.Therefore,by studying the formation and orbital transformation mechanism of satellites,planets and stars,the author puts forward a new theory on the formation and evolution of stars and galaxies,thus revealing the hierarchical structure of galaxies and the formation and evolution laws of main sequence stars,red giants,white dwarfs,black dwarfs,supernovae,neutron stars,black holes and quasars.Some special phenomena in the course of star formation and evolution,such as sunspots,flares,fast radio bursts and gamma-ray bursts,have also been revealed.
文摘针对美国空管部门的机场终端区空管自动化系统(Standard Terminal Automation Replacement System,STARS)中降水资料的诸多不足,按照新一代航空运输系统要求,美国联邦航空管理局(FAA)正组织研究“新一代机场终端区降水显示产品”(Terminal Precipitation on the Glass,TPoG)。TPoG项目利用源自美国新一代天气系统(NextGen天气系统)的高精度国家天气雷达数据,显著提升空管自动化系统中降水信息的精度和可靠性,进而提升空管指挥与空中飞行的安全与效率。文中介绍了中国民航与TPoG相类似的几种气象-空管融合产品在流量管理和管制指挥等方面的研究进展及业务应用情况,并探讨中国民航气象服务在气象-空管融合领域的发展方向。
基金supported by NSFC(Nos.12161141003,11931006)supported by NSFC(Nos.11801520,12171436,12271489)supported by NSFC(No.11601527)。
文摘For k given graphs H_(1),...,H_(k) with k≥2,the k-color Ramsey number R(H_(1),...,H_(k)) represents the minimum integer N with the following property:if the edges of the complete graph K_(N) are colored with k colors,then there exists some i with 1≤i≤k such that K_(N) has a subgraph in color i isomorphic to H_(i).Let C_(m) be a cycle of length m and K_(1,n) a star of order n+1.In this paper,we systematically introduce the latest research progress on star-quadrilateral Ramsey numbers and provide an overview of Ramsey numbers concerning quadrilaterals,including multicolor cases.
基金supported by the National Natural Science Foundation of China(12273008,12025303,12403046)the National SKA Program of China(2022SKA0130104)+3 种基金the Natural Science and Technology Foundation of Guizhou Province(QiankehejichuMS[2025]266,[2023]024,ZK[2022]304)the Foundation of Guizhou Provincial Education Department(KY(2020)003)the Academic New Seedling Fund Project of Guizhou Normal University([2022]B18)the Major Science and Technology Program of Xinjiang Uygur Autonomous Region(2022A03013-4).
文摘The emission of anomalous X-ray pulsars(AXPs)and soft gamma-ray repeaters(SGRs)is believed to be powered by the dissipation of their strong magnetic fields,which coined the name“magnetar”.By combining timing and energy observational results,the magnetar model can be easily appreciated.From a timing perspective,the magnetic field strengths of AXPs and SGRs,which are calculated under the assumption of dipole radiation,are extremely strong.From an energy perspective,the X-ray/soft gamma-ray luminosities of AXPs and SGRs are larger than their rotational energy loss rates(i.e.,L_(x>E_(rot)).It is thus reasonable to assume that the high-energy radiation comes from magnetic energy decay,and the magnetar model has been extensively discussed(or accepted).However,we argue that:(ⅰ)Calculating magnetic fields by assuming that rotational energy loss is dominated by dipole radiation(i.e.,E_(rot)■E_(μ))may be controversial,and we suggest that the energies carried by outflowing particles should also be considered.(ⅱ)The fact that X-ray luminosity is greater than the rotational energy loss rate does not necessarily mean that the emission energy comes from the magnetic field decaying,which requires further observational testing.Furthermore,some observational facts conflict with the“magnetar”model,such as observations of anti-magnetars,high magnetic field pulsars,and radio and X-ray observations of AXPs/SGRs.Therefore,we propose a crusted strange star model as an alternative,which can explain many more observational facts of AXPs/SGRs.
文摘AR Aur A+B is a close binary of astrophysical interest because dissimilar surface compositions are reported between similar late B-type dwarfs.A new spectroscopic study on this system was carried out based on the disentangled spectra,in order to determine their atmospheric parameters and elemental abundances.The effective temperature and microturbulence(determined from the equivalent widths of Fe II lines)turned out to be(11,150 K,0.9 km s^(-1))and(10,650 K,0.1 km s^(-1))for A and B,respectively.The chemical abundances of 28 elements were then derived while taking into account the non-LTE effect for Z≤15 elements(Z:atomic number).The following trends were elucidated for[X/H](abundance of X relative to the Sun):(1)Qualitatively,[X/H]shows a rough global tendency to increase with Z,with the gradient steeper for A than for B.(2)However,considerable dispersion is involved for A,since prominently large peculiarities are seen in specific elements reflecting the characteristics of HgMn stars(e.g.,very deficient N,Al,Sc,Ni;markedly overabundant P,Mn).(3)In contrast,the Z-dependence of[X/H]for B tends to be nearly linear with only a small dispersion.These observational facts may serve as a key to understanding the critical condition for the emergence of the chemical anomaly.
基金funded by the National Natural Science Foundation of China(Nos.42374011,42074013)through the Natural Science Foundation’s Outstanding Youth Fund Program of Henan Province,China(Nos.242300421150,242300421151)。
文摘Daytime star images captured by dedicated near-space star sensors are characterized by short exposures,high noise,and low Signal-to-Noise Ratios(SNRs).Such imaging is also affected by atmospheric turbulence,causing optical phenomena,such as scintillation,distortion,and jitter.This causes difficulty in recording high-precision star images during the daytime.This study proposes an adaptive star point extraction method based on dynamically predicting stars'positions.First,it predicts the approximate position of stars based on the star catalog,sensor attitude,observation time,and other information,improving the extraction accuracy.Second,it employs a regional SNR sorting method that adaptively selects star images with higher SNRs,suppressing the scintillation effect and enhancing the SNR of star images.Third,depending on the star's motion trajectory characteristics on the image plane,it utilizes the centroid smoothing method for extraction,thus overcoming the impact of star drift.Field experiments demonstrate that the proposed method can effectively overcome star scintillation,drift,and irregular imaging caused by atmospheric turbulence,achieving a 100%success rate.Moreover,the extraction accuracy improves by more than 80%compared to traditional adaptive methods,attaining a value of 0.05 pixels(0.5"),thereby meeting the requirements of daytime astronomical attitude determination and positioning.
文摘In the current paper,we present a study of the spatial distribution of luminous blue variables(LBVs)and various LBV candidates(c LBVs)with respect to OB associations in the galaxy M33.The identification of blue star groups was based on the LGGS data and was carried out by two clustering algorithms with initial parameters determined during simulations of random stellar fields.We have found that the distribution of distances to the nearest OB association obtained for the LBV/c LBV sample is close to that for massive stars with Minit>20 M⊙and WolfRayet stars.This result is in good agreement with the standard assumption that LBVs represent an intermediate stage in the evolution of the most massive stars.However,some objects from the LBV/cLBV sample,particularly Fe II-emission stars,demonstrated severe isolation compared to other massive stars,which,together with certain features of their spectra,implicitly indicates that the nature of these objects and other LBVs/cLBVs may differ radically.
基金A grant from the Pazy Foundation supported this research。
文摘We demonstrate by three-dimensional hydrodynamical simulations of energy deposition into the envelope of a red supergiant model the inflation of a Rayleigh–Taylor unstable envelope that forms a compact clumpy circumstellar material(CSM).Our simulations mimic vigorous core activity years to months before a core-collapse supernova(CCSN)explosion that deposits energy to the outer envelope.The fierce core nuclear activity in the pre-CCSN explosion phase might excite waves that propagate to the envelope.The wave energy is dissipated where envelope convection cannot carry the energy.We deposit this energy into a shell in the outer envelope with a power of L_(wave)=2.6×10^(6)L■or L_(wave)=5.2×10^(5)L■for 0.32 yr.The energy-deposition shell expands while its pressure is higher than its surroundings,but its density is lower.Therefore,this expansion is Rayleigh–Taylor unstable and develops instability fingers.Most of the inflated envelope does not reach the escape velocity in the year of simulation but forms a compact and clumpy CSM.The high density of the inflated envelope implies that if a companion is present in that zone,it will accrete mass at a very high rate and power a pre-explosion outburst.
基金DST,Government of India for the award of INSPIRE fellowship(IF230384)。
文摘Despite many attempts,the origin of UV emission line and continuum in contact binary stars remains unclear.We present a substantial UV spectroscopic analysis of VW Cephei,a late-type contact binary system,using 46 lowresolution spectra from the International Ultraviolet Explorer in the wavelength range 1150-1978À.By modeling continuum and emissions lines in individual spectra,we report the significant detection of O Ⅲ](1660 and 1666À)and Si Ⅳ(1393 and 1402À)line complexes.We observe that UV fluxes for both continuum and emission lines like C Ⅳ,O Ⅲ],C Ⅱ and Si Ⅳ vary significantly(fractional rms variability up to 45%)from hours to years.In addition,line widths also change by hundreds of km s^(-1).The UV flux variabilities observed in the continuum bands and line emissions are uncorrelated.However,most of the flux values follow the binary orbital period observed from optical data.Our analysis indicates that,while the variation in continuum flux may be attributed to a heated photosphere,the line width measurements indicate that the emission lines are likely formed in the dynamical clouds associated with Roche lobe overflow.We estimate the mass transfer rate of M=(0.82±0.01)×10^(-7)M_(⊙)yr^(-1)from UV line fluxes,which is in good agreement with optical studies.
