In the Lower CretaceousMcMurray-Clearwater succession of the intracontinental Alberta Foreland Basin,Canada,detrital zircon U-Pb geochronology samples(referred to herein as DZ samples)have been used to interpret the s...In the Lower CretaceousMcMurray-Clearwater succession of the intracontinental Alberta Foreland Basin,Canada,detrital zircon U-Pb geochronology samples(referred to herein as DZ samples)have been used to interpret the strata as representing a paleo-continental-scale drainage system.However,the majority of DZ samples are relatively small(n≈90–100),and syndepositional DZ(i.e.,crystallization age<5 Ma older than depositional age)are rare.This has forced a reliance on dinocysts with long stratigraphic ranges to chronostratigraphically subdivide the McMurray-Clearwater succession rather than employing maximum depositional ages(MDAs)derived from DZ samples.Herein,43 DZ samples(taken from20 subsurface cores)are assigned to 1 of 5 stratigraphic intervals,and in each stratigraphic interval all associated DZ samples are combined to produce a grouped DZ sample.Analysis and comparison of individual and grouped DZ samples are used to(1)assess variability in provenance through time and space,and(2)assess the accuracy of chronostratigraphically subdividing the succession using MDAs.Along the main paleo-drainage axis,a comparison of dissimilarity between DZ samples from the same stratigraphic interval,as well as between stratigraphic intervals,reveals increasing average dissimilarity between individual DZ samples and their respective grouped DZ samplewith increasing spatial separation of samples.These data indicate that in the McMurray Depocenter some sediment is sourced from local tributaries,leading to geographical provenance variability.CalculatedMDAs for all 43 DZ samples and groupedMDAs(gMDAs)for the 5 grouped DZ samples are compared to an ash-derived absolute age and existing biostratigraphy.In theMcMurray Formation,comparison of MDAs to gMDAs shows that in basins with rare syndepositional DZ,the gMDA method improved depositional age estimates by transforming low-confidence MDAs(e.g.,youngest single grains)into high-confidence(multi-grain)gMDAs.In the Clearwater Formationwhere syndepositional DZ are plentiful(i.e.,>5%of the total DZ population),calculating maximumlikelihood ages fromgrouped DZ samples avoids negatively biased(i.e.,too young)MDAs.We suggest grouped DZ samples and the gMDA method be used in systems with multiple DZ samples from a well-defined stratigraphic interval as a means of assessing variability in provenancewithin a depositional system and for improving estimates of depositional ages using DZ.展开更多
By using of electrolytic pure iron, the specimens containing different oxide content were made in a Mo wire furnace. The DTA method was employed to measure the undercooling of liquid iron during solidification. The re...By using of electrolytic pure iron, the specimens containing different oxide content were made in a Mo wire furnace. The DTA method was employed to measure the undercooling of liquid iron during solidification. The relations between the cleanness of liquid iron and undercooling, thermodynamic driving force of nucleation, the nucleus forming energy, as well as the critical radius of nucleus have been investigated. The results showed that with the increase of cleanness of liquid iron the undercooling and thermodynamic driving force increased, while the nucleus forming energy and critical radius of nucleus decreased.展开更多
In this paper,we report the detection of the very-high-energy(VHE,100 GeV<E<100 TeV)and ultra-high-energy(UHE,E>100 TeV)y-ray emissions from the direction of the young star-forming region W43,observed by the ...In this paper,we report the detection of the very-high-energy(VHE,100 GeV<E<100 TeV)and ultra-high-energy(UHE,E>100 TeV)y-ray emissions from the direction of the young star-forming region W43,observed by the Large High Altitude Air Shower Observation(LHAASO).The extendedγ-ray source was detected with a significance of~16σby KM2A and~17σby WCDA,respectively.The angular extension of this y-ray source is about 0.5 degrees,corresponding to a physical size of about 50pc.We discuss the origin of theγ-ray emission and possible cosmic ray acceleration in the W43 region using multi-wavelength data.Our findings suggest that W43 is likely another young star cluster capable of accelerating cosmic rays(CRs)to at least several hundred TeV.展开更多
We report the detection of an extended very-high-energy(VHE)γ-ray source coincident with the location of middle-aged(62.4 kyr)pulsar PSR J0248+6021,by using the LHAASO-WCDA data of live 796 d and LHAASO-KM2A data of ...We report the detection of an extended very-high-energy(VHE)γ-ray source coincident with the location of middle-aged(62.4 kyr)pulsar PSR J0248+6021,by using the LHAASO-WCDA data of live 796 d and LHAASO-KM2A data of live 1216d.A significant excess of y-ray induced showers is observed both by WCDA in energy bands of 1-25 TeV and KM2A in energy bands of>25 TeV with 7.3σand 13.5σ,respectively.The best-fit position derived through WCDA data is R.A.=42.06°±0.12°and Dec.=60.24°±0.13°with an extension of 0.69°±0.15°and that of the KM2A data is R.A.=42.29°±0.13°and Dec.=60.38°±0.07°with an extension of 0.37°±0.07°.No clear extended multiwavelength counterpart of this LHAASO source has been found from the radio band to the GeV band.The most plausible explanation of the VHEγ-ray emission is the inverse Compton process of highly relativistic electrons and positrons injected by the pulsar.These electrons/positrons are hypothesized to be either confined within the pulsar wind nebula or to have already escaped into the interstellar medium,forming a pulsar halo.展开更多
We report a dedicated study of the newly discovered extended UHEγ-ray source 1LHAASO J0056+6346u.Analyzing 979 d of LHAASO-WCDA data and 1389 d of LHAASO-KM2A data,we observed a significant excess ofγ-ray events wit...We report a dedicated study of the newly discovered extended UHEγ-ray source 1LHAASO J0056+6346u.Analyzing 979 d of LHAASO-WCDA data and 1389 d of LHAASO-KM2A data,we observed a significant excess ofγ-ray events with both WCDA and KM2A.Assuming a point power-law source with a fixed spectral index,the significance maps reveal excesses of 12.65σ,22.18σ,and 10.24σin the energy ranges of 1-25,25-100,and>100 TeV,respectively.We use a 3D likelihood algorithm to derive the morphological and spectral parameters,and the source is detected with significances of 13.72σby WCDA and 25.27σby KM2A.The best-fit positions derived from WCDA and KM2A data are(R.A.=13.96°±0.09°,Decl.=63.92°±0.05°)and(R.A.=14.00°±0.05°,Decl.=63.79°±0.02°),respectively.The angular size(r_(39))of 1LHAASO J0056+6346u is 0.34°±0.04°at 1-25 TeV and 0.24°±0.02°at>25 TeV.The differential flux of this UHEγ-ray source can be described by an exponential cutoff power-law function:(2.67±0.25)×10^(-15)(E/20 TeV)^((-1.97±0.10))e^(-E/(55.1±7.2)TeV)TeV^(-1)cm^(-2)s^(-1).To explore potential sources ofγ-ray emission,we investigated the gas distribution around 1LHAASO J0056+6346u.1LHAASO J0056+6346u is likely to be a TeV PWN powered by an unknown pulsar,which would naturally explain both its spatial and spectral properties.Another explanation is that this UHEγ-ray source might be associated with gas content illuminated by a nearby CR accelerator,possibly the SNR candidate G124.0+1.4.展开更多
We report the high-purity identification of cosmic-ray(CR)protons and a precise measurement of their energy spectrum from 0.15 to 12 PeV using the Large High Altitude Air Shower Observatory(LHAASO).Abundant event stat...We report the high-purity identification of cosmic-ray(CR)protons and a precise measurement of their energy spectrum from 0.15 to 12 PeV using the Large High Altitude Air Shower Observatory(LHAASO).Abundant event statistics,combined with the simultaneous detection of electrons/photons,muons,and Cherenkov light in air showers,enable spectroscopic measurements with statistical and systematic precision comparable to satellite data at lower energies.The proton spectrum shows significant hardening relative to low-energy extrapolations,culminating at 3 PeV,followed by sharp softening.This distinct spectral structure closely aligned with the knee in the all-particle spectrum points to the emergence of a new CR component at PeV energies that might be linked to the dozens of PeVatrons recently discovered by LHAASO,and offers crucial clues to the origin of Galactic cosmic rays.展开更多
The ultra-high-energy(UHE)gamma-ray source 1LHAASO J0007+7303u is positionally associated with the composite SNR CTA1 that is located at high Galactic Latitude b≈10.5°.This provides a rare opportunity to spatial...The ultra-high-energy(UHE)gamma-ray source 1LHAASO J0007+7303u is positionally associated with the composite SNR CTA1 that is located at high Galactic Latitude b≈10.5°.This provides a rare opportunity to spatially resolve the component of the pulsar wind nebula(PWN)and supernova remnant(SNR)at UHE.This paper conducted a dedicated data analysis of 1LHAASO J0007+7303u using the data collected from December 2019 to July 2023.This source is well detected with significances of 21σand 17σat 8-100 TeV and>100 TeV,respectively.The corresponding extensions are determined to be 0.23°±0.03°and 0.17°±0.03°.The emission is proposed to originate from the relativistic electrons accelerated within the PWN of PSR J0007+7303.The energy spectrum is well described by a power-law with an exponential cutoff function dN/dE=(42.4±4.1)(E/20TeV)^(-2.31+0.11)exp(-E/(110±25Tev))TeV-1 cm^(-2)s^(-1)in the energy range from 8 to 300 TeV,implying a steady-state parent electron spectrum dN_(e)/dE_(e)∝(E_(e)/100TeV)^(-3.13±0.16)exp[(-E_(e)/(373±70TeV))^(2)]at energies above≈50 TeV.The cutoff energy of the electron spectrum is roughly equal to the expected current maximum energy of particles accelerated at the PWN terminal shock.Combining the X-ray and gamma-ray emission,the current space-averaged magnetic field can be limited to≈4.5μG.To satisfy the multi-wavelength spectrum and the y-ray extensions,the transport of relativistic particles within the PWN is likely dominated by the advection process under the free-expansion phase assumption.展开更多
Chinese tamarisk(saltcedar)is a deciduous shrub that occurs widely across the Yellow River Delta in China.The spatial structure of Chinese tamarisk is believed to have an influence on the landscape and habitats of rar...Chinese tamarisk(saltcedar)is a deciduous shrub that occurs widely across the Yellow River Delta in China.The spatial structure of Chinese tamarisk is believed to have an influence on the landscape and habitats of rare birds.In this study,first,Chinese tamarisk is detected using Canny edge detector and mathematical morphological operators based on SPOT 5 fusion-ready imagery.Then the numbers,areas,locations,and patch spacing of Chinese tamarisk patches are calculated.The experiments show that the detection accuracy of Chinese tamarisk patches is about 93.4%after the disconnection of connected patches.The distribution orientation of about 70%of the patches is approximately south-north.About 91%of the minimum distances among the patches are between 12.5 and 57.5 m.The rose graph indicates that the main azimuth between patches is north--northwest,and the second is northeast and southeast.The present study indicates that the integrating Canny edge detector with the algorithms for extracting circular and elliptical objects based on mathematical morphology is simple and effective for detecting Chinese tamarisk patches and is easy to identify the spatial structure of Chinese tamarisk patches,which reduces the time and labor for the visual interpretation of Chinese tamarisk patches.展开更多
基金We acknowledge BP plc,Cenovus Energy,Husky Energy,Nexen CNOOC Ltd.,and Woodside Energy Ltd.for funding the McMurray Research Consortium,and GeoLOGIC for providing the GeoScout software used in this study.
文摘In the Lower CretaceousMcMurray-Clearwater succession of the intracontinental Alberta Foreland Basin,Canada,detrital zircon U-Pb geochronology samples(referred to herein as DZ samples)have been used to interpret the strata as representing a paleo-continental-scale drainage system.However,the majority of DZ samples are relatively small(n≈90–100),and syndepositional DZ(i.e.,crystallization age<5 Ma older than depositional age)are rare.This has forced a reliance on dinocysts with long stratigraphic ranges to chronostratigraphically subdivide the McMurray-Clearwater succession rather than employing maximum depositional ages(MDAs)derived from DZ samples.Herein,43 DZ samples(taken from20 subsurface cores)are assigned to 1 of 5 stratigraphic intervals,and in each stratigraphic interval all associated DZ samples are combined to produce a grouped DZ sample.Analysis and comparison of individual and grouped DZ samples are used to(1)assess variability in provenance through time and space,and(2)assess the accuracy of chronostratigraphically subdividing the succession using MDAs.Along the main paleo-drainage axis,a comparison of dissimilarity between DZ samples from the same stratigraphic interval,as well as between stratigraphic intervals,reveals increasing average dissimilarity between individual DZ samples and their respective grouped DZ samplewith increasing spatial separation of samples.These data indicate that in the McMurray Depocenter some sediment is sourced from local tributaries,leading to geographical provenance variability.CalculatedMDAs for all 43 DZ samples and groupedMDAs(gMDAs)for the 5 grouped DZ samples are compared to an ash-derived absolute age and existing biostratigraphy.In theMcMurray Formation,comparison of MDAs to gMDAs shows that in basins with rare syndepositional DZ,the gMDA method improved depositional age estimates by transforming low-confidence MDAs(e.g.,youngest single grains)into high-confidence(multi-grain)gMDAs.In the Clearwater Formationwhere syndepositional DZ are plentiful(i.e.,>5%of the total DZ population),calculating maximumlikelihood ages fromgrouped DZ samples avoids negatively biased(i.e.,too young)MDAs.We suggest grouped DZ samples and the gMDA method be used in systems with multiple DZ samples from a well-defined stratigraphic interval as a means of assessing variability in provenancewithin a depositional system and for improving estimates of depositional ages using DZ.
基金sponsored by National 973 Research Program(No.J1998061511-2).
文摘By using of electrolytic pure iron, the specimens containing different oxide content were made in a Mo wire furnace. The DTA method was employed to measure the undercooling of liquid iron during solidification. The relations between the cleanness of liquid iron and undercooling, thermodynamic driving force of nucleation, the nucleus forming energy, as well as the critical radius of nucleus have been investigated. The results showed that with the increase of cleanness of liquid iron the undercooling and thermodynamic driving force increased, while the nucleus forming energy and critical radius of nucleus decreased.
基金supported by the National Natural Science Foundation of China(Grant Nos.12393854,12175121,12393851,12393852,12393853,12205314,12105301,12305120,12261160362,12105294,U1931201,12375107,and 12173039)the Department of Science and Technology of Sichuan Province,China(Grant No.24NSFSC2319)+2 种基金Project for Young Scientists in Basic Research of Chinese Academy of Sciences(Grant No.YSBR-061)in Thailand by the National Science and Technology Development Agency(NSTDA)the National Research Council of Thailand(NRCT)under the High-Potential Research Team Grant Program(Grant No.N42A650868)。
文摘In this paper,we report the detection of the very-high-energy(VHE,100 GeV<E<100 TeV)and ultra-high-energy(UHE,E>100 TeV)y-ray emissions from the direction of the young star-forming region W43,observed by the Large High Altitude Air Shower Observation(LHAASO).The extendedγ-ray source was detected with a significance of~16σby KM2A and~17σby WCDA,respectively.The angular extension of this y-ray source is about 0.5 degrees,corresponding to a physical size of about 50pc.We discuss the origin of theγ-ray emission and possible cosmic ray acceleration in the W43 region using multi-wavelength data.Our findings suggest that W43 is likely another young star cluster capable of accelerating cosmic rays(CRs)to at least several hundred TeV.
基金supported by the National Natural Science Foundation of China(Grant Nos.12393854,12393851,12393852,12393853,12205314,12105301,12305120,12261160362,12105294,U1931201,12375107,and 12173039)the Department of Science and Technology of Sichuan Province,China(Grant No.24NSFSC2319)+2 种基金the Project for Young Scientists in Basic Research of Chinese Academy of Sciences(Grant No.YSBR-061)in Thailand by the National Science and Technology Development Agency(NSTDA)the National Research Council of Thailand(NRCT)under the High-Potential Research Team Grant Program(Grant No.N42A650868)。
文摘We report the detection of an extended very-high-energy(VHE)γ-ray source coincident with the location of middle-aged(62.4 kyr)pulsar PSR J0248+6021,by using the LHAASO-WCDA data of live 796 d and LHAASO-KM2A data of live 1216d.A significant excess of y-ray induced showers is observed both by WCDA in energy bands of 1-25 TeV and KM2A in energy bands of>25 TeV with 7.3σand 13.5σ,respectively.The best-fit position derived through WCDA data is R.A.=42.06°±0.12°and Dec.=60.24°±0.13°with an extension of 0.69°±0.15°and that of the KM2A data is R.A.=42.29°±0.13°and Dec.=60.38°±0.07°with an extension of 0.37°±0.07°.No clear extended multiwavelength counterpart of this LHAASO source has been found from the radio band to the GeV band.The most plausible explanation of the VHEγ-ray emission is the inverse Compton process of highly relativistic electrons and positrons injected by the pulsar.These electrons/positrons are hypothesized to be either confined within the pulsar wind nebula or to have already escaped into the interstellar medium,forming a pulsar halo.
基金supported by the National Natural Science Foundation of China(Grant Nos.12393854,12393851,12393852,12393853,12205314,12105301,12305120,12261160362,12105294,U1931201,12375107,and 12173039)the Department of Science and Technology of Sichuan Province,China(Grant Nos.24NSFSC2319,and 2024NSFSC0449)+5 种基金the Project for Young Scientists in Basic Research of Chinese Academy of Sciences(Grant No.YSBR-061)in Thailand by the National Science and Technology Development Agency(NSTDA)the National Research Council of Thailand(NRCT)under the High-Potential Research Team Grant Program(Grant No.N42A650868)supported by the National Key R&D Program of China(Grant Nos.2023YFA1608000,and 2017YFA0402701)the CAS Key Research Program of Frontier Sciences(Grant No.QYZDJ-SSW-SLH047)used data from the Canadian Galactic Plane Survey,a Canadian project with international partners,supported by the Natural Sciences and Engineering Research Council。
文摘We report a dedicated study of the newly discovered extended UHEγ-ray source 1LHAASO J0056+6346u.Analyzing 979 d of LHAASO-WCDA data and 1389 d of LHAASO-KM2A data,we observed a significant excess ofγ-ray events with both WCDA and KM2A.Assuming a point power-law source with a fixed spectral index,the significance maps reveal excesses of 12.65σ,22.18σ,and 10.24σin the energy ranges of 1-25,25-100,and>100 TeV,respectively.We use a 3D likelihood algorithm to derive the morphological and spectral parameters,and the source is detected with significances of 13.72σby WCDA and 25.27σby KM2A.The best-fit positions derived from WCDA and KM2A data are(R.A.=13.96°±0.09°,Decl.=63.92°±0.05°)and(R.A.=14.00°±0.05°,Decl.=63.79°±0.02°),respectively.The angular size(r_(39))of 1LHAASO J0056+6346u is 0.34°±0.04°at 1-25 TeV and 0.24°±0.02°at>25 TeV.The differential flux of this UHEγ-ray source can be described by an exponential cutoff power-law function:(2.67±0.25)×10^(-15)(E/20 TeV)^((-1.97±0.10))e^(-E/(55.1±7.2)TeV)TeV^(-1)cm^(-2)s^(-1).To explore potential sources ofγ-ray emission,we investigated the gas distribution around 1LHAASO J0056+6346u.1LHAASO J0056+6346u is likely to be a TeV PWN powered by an unknown pulsar,which would naturally explain both its spatial and spectral properties.Another explanation is that this UHEγ-ray source might be associated with gas content illuminated by a nearby CR accelerator,possibly the SNR candidate G124.0+1.4.
基金supported by the National Key R&D Program of China(2024YFA1611401,2024YFA1611402,2024YFA1611403,and 2024YFA1611404)the National Natural Science Foundation of China(12393851,12393852,12393853,12393854,12205314,12105301,12305120,12261160362,12105294,U1931201,12375107,12275280,12105293,11905240,12375106,and 12261141691)+3 种基金Innovation Project of IHEP(E25451U2)Sichuan Province Science Foundation for Distinguished Young Scholars(2022JDJQ0043)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(CAS YIPA)(2023019)the Institute of Plateau Meteorology,CMA Chengdu to maintain meteorological data,and Thailand’s National Science and Technology Development Agency(NSTDA)and National Research Council of Thailand(NRCT)under the High-Potential Research Team Grant Program(N42A650868)。
文摘We report the high-purity identification of cosmic-ray(CR)protons and a precise measurement of their energy spectrum from 0.15 to 12 PeV using the Large High Altitude Air Shower Observatory(LHAASO).Abundant event statistics,combined with the simultaneous detection of electrons/photons,muons,and Cherenkov light in air showers,enable spectroscopic measurements with statistical and systematic precision comparable to satellite data at lower energies.The proton spectrum shows significant hardening relative to low-energy extrapolations,culminating at 3 PeV,followed by sharp softening.This distinct spectral structure closely aligned with the knee in the all-particle spectrum points to the emergence of a new CR component at PeV energies that might be linked to the dozens of PeVatrons recently discovered by LHAASO,and offers crucial clues to the origin of Galactic cosmic rays.
基金in China by the National Natural Science Foundation of China(Grant Nos.12393851,12393854,12393852,12393853,12022502,12205314,12105301,12261160362,12105294,U1931201,and 2024NSFJQ0060)in Thailand by the National Science and Technology Development Agency(NSTDA)the National Research Council of Thailand(NRCT)under the High-Potential Research Team Grant Program(Grant No.N42A650868)。
文摘The ultra-high-energy(UHE)gamma-ray source 1LHAASO J0007+7303u is positionally associated with the composite SNR CTA1 that is located at high Galactic Latitude b≈10.5°.This provides a rare opportunity to spatially resolve the component of the pulsar wind nebula(PWN)and supernova remnant(SNR)at UHE.This paper conducted a dedicated data analysis of 1LHAASO J0007+7303u using the data collected from December 2019 to July 2023.This source is well detected with significances of 21σand 17σat 8-100 TeV and>100 TeV,respectively.The corresponding extensions are determined to be 0.23°±0.03°and 0.17°±0.03°.The emission is proposed to originate from the relativistic electrons accelerated within the PWN of PSR J0007+7303.The energy spectrum is well described by a power-law with an exponential cutoff function dN/dE=(42.4±4.1)(E/20TeV)^(-2.31+0.11)exp(-E/(110±25Tev))TeV-1 cm^(-2)s^(-1)in the energy range from 8 to 300 TeV,implying a steady-state parent electron spectrum dN_(e)/dE_(e)∝(E_(e)/100TeV)^(-3.13±0.16)exp[(-E_(e)/(373±70TeV))^(2)]at energies above≈50 TeV.The cutoff energy of the electron spectrum is roughly equal to the expected current maximum energy of particles accelerated at the PWN terminal shock.Combining the X-ray and gamma-ray emission,the current space-averaged magnetic field can be limited to≈4.5μG.To satisfy the multi-wavelength spectrum and the y-ray extensions,the transport of relativistic particles within the PWN is likely dominated by the advection process under the free-expansion phase assumption.
基金supported by a grant from the National Natural Science Foundation of China(Project No.41023010)a grant from the Strategic Priority Research Program of Chinese Academy of Sciences(Project No.XDA05050601).
文摘Chinese tamarisk(saltcedar)is a deciduous shrub that occurs widely across the Yellow River Delta in China.The spatial structure of Chinese tamarisk is believed to have an influence on the landscape and habitats of rare birds.In this study,first,Chinese tamarisk is detected using Canny edge detector and mathematical morphological operators based on SPOT 5 fusion-ready imagery.Then the numbers,areas,locations,and patch spacing of Chinese tamarisk patches are calculated.The experiments show that the detection accuracy of Chinese tamarisk patches is about 93.4%after the disconnection of connected patches.The distribution orientation of about 70%of the patches is approximately south-north.About 91%of the minimum distances among the patches are between 12.5 and 57.5 m.The rose graph indicates that the main azimuth between patches is north--northwest,and the second is northeast and southeast.The present study indicates that the integrating Canny edge detector with the algorithms for extracting circular and elliptical objects based on mathematical morphology is simple and effective for detecting Chinese tamarisk patches and is easy to identify the spatial structure of Chinese tamarisk patches,which reduces the time and labor for the visual interpretation of Chinese tamarisk patches.
