The axion,a leading dark matter(DM)candidate,can convert to photons in neutron star(NS)magnetospheres via the Primakoff effect,producing narrow-band radio emission that may be detected with high-sensitivity radio tele...The axion,a leading dark matter(DM)candidate,can convert to photons in neutron star(NS)magnetospheres via the Primakoff effect,producing narrow-band radio emission that may be detected with high-sensitivity radio telescopes.Previous studies searched for axion DM-induced signals from the isolated NS J0806.4-4123 using observations of the Meer KAT UHF band(544–1088 MHz),but excluded the 1051–1088 MHz subband to mitigate potential sideband contamination.To probe this unexplored parameter space,we reprocessed the 1000–1088 MHz subband data using optimized radio frequency interference(RFI)flagging and meticulous sideband calibration.The flux stability of the calibrators and the consistency with Meer KAT’s system equivalent flux density confirmed the reliability of the data within the 1000–1080 MHz range,while the 1080–1088 MHz subband was omitted due to flux anomalies.No significant signals exceeding 5σsignificance were detected within the axion mass range of 4.136–4.467μe V(1000–1080 MHz),including the previously unprobed range 4.347–4.467μe V(1051–1080 MHz).Our null detection sets new stringent constraints with Meer KAT NS data,excluding axion-photon couplings|g_(aγγ)|?8.2×10^(-12)Ge V^(-1)at the 95%confidence level for DM masses between 4.347 and 4.467μe V.展开更多
We present the first search for pulsed CH maser emission potentially stimulated by PSR J1644-4559,conducted using the ultra-wide-bandwidth low-frequency receiver on Murriyang,CSIRO's Parkes Radio Telescope.Observa...We present the first search for pulsed CH maser emission potentially stimulated by PSR J1644-4559,conducted using the ultra-wide-bandwidth low-frequency receiver on Murriyang,CSIRO's Parkes Radio Telescope.Observations targeted three CHΛ-doublet transitions at 3264,3335,and 3349 MHz,with a variability timescale of78 ms.We detected ten CH emission features at 3335 and 3349 MHz,and seven features at 3264 MHz,during both pulsar-ON and pulsar-OFF phases.The observed velocities align with the OH emission and absorption reported by a previous study,suggesting a close spatial association between CH and OH molecules.The derived column densities for CH clouds within the Parkes beam range from 0.05 to 9.8×10^(13)cm^(-2),indicating that these clouds are likely in diffuse and translucent states.Upper limits for CH column densities within the pulsar beam ranged from 0.3 to 9.8×10^(13)cm^(-2).Comparison of these column densities suggests that CH clouds may exhibit clumpiness and substructure.No significant stimulated emission feature was detected in the optical depth spectra.Additionally,as part of our search for pulsed stimulated emission,we investigated the potential CH absorption of the pulsar signal and found none,in agreement with astrophysical expectations.The upper limits for the potential maser amplification factors towards PSR J1644-4559 at 3264,3335,and 3349 MHz are 1.014,1.009,and 1.009,respectively.This study demonstrates the feasibility of detecting pulsed CH maser emission in the interstellar medium stimulated by pulsar photons.展开更多
Molecular oxygen abundance is a key parameter in understanding the chemical network of the interstellar medium.We estimate the molecular oxygen column density and abundance for a sample of Galactic massive star format...Molecular oxygen abundance is a key parameter in understanding the chemical network of the interstellar medium.We estimate the molecular oxygen column density and abundance for a sample of Galactic massive star formation regions based on observations from the Submillimiter Wave Astronomy Satellite(SWAS)survey.We obtained an averaged O_(2)spectrum based on this sample using the(SWAS)survey data(O_(2),487.249 GHz,N=3-1,J=3-2).No emission or absorption feature is seen around the supposed central velocity with a total integration time of t_(total)=8.67×10^(3)hr and an rms noise per channel of 1.45 m K.Assuming a kinetic temperature T_(kin)=30 K,we derive the 3σupper limit of the O_(2)column density to be 3.3×10^(15)cm^(-2),close to the lowest values reported in Galactic massive star formation regions in previous studies.The corresponding O_(2)abundance upper limit is6.7×10^(-8),lower than all previous results based on SWAS observations and is close to the lowest reported value in massive star formation regions.On a galactic scale,our statistical results confirm a generally low O_(2)abundance for Galactic massive star formation regions.This abundance is also lower than results reported in extragalactic sources.展开更多
We used the Five-hundred-meter Aperture Spherical radio Telescope(FAST)to search for the molecular emissions in the L-band between 1.0 and 1.5 GHz toward four comets,C/2020 F3(NEOWISE),C/2020 R4(ATLAS),C/2021 A1(Leona...We used the Five-hundred-meter Aperture Spherical radio Telescope(FAST)to search for the molecular emissions in the L-band between 1.0 and 1.5 GHz toward four comets,C/2020 F3(NEOWISE),C/2020 R4(ATLAS),C/2021 A1(Leonard),and 67P/Churyumov-Gerasimenko during or after their perihelion passages.Thousands of molecular transition lines fall in this low-frequency range,many attributed to complex organic or prebiotic molecules.We conducted a blind search for the possible molecular lines in this frequency range in those comets and could not identify clear signals of molecular emissions in the data.Although several molecules have been detected at high frequencies of greater than100 GHz in comets,our results confirm that it is challenging to detect molecular transitions in the L-band frequency ranges.The non-detection of L-band molecular lines in the cometary environment could rule out the possibility of unusually strong lines,which could be caused by the masers or non-LTE effects.Although the line strengths are predicted to be weak,for FAST,using the ultra-wide bandwidth receiver and improving the radio frequency interference environments would enhance the detectability of those molecular transitions at low frequencies in the future.展开更多
Sulfur-bearing species are widely utilized to investigate the physical structure of star-forming regions in interstellar media;however,the underlying sulfur chemistry in these environments remains poorly understood.Th...Sulfur-bearing species are widely utilized to investigate the physical structure of star-forming regions in interstellar media;however,the underlying sulfur chemistry in these environments remains poorly understood.Therefore,further studies of S-bearing species are fundamentally important,as they can enhance our understanding of the physical evolution of star-forming regions.This study presents observations of C_(2)S and C_(3)S in L1544,acquired using the Nanshan 26-m radio telescope,along with simulations of their chemical behavior using a one-dimensional physical model.The simulation results reveal significant radial variations in the column densities of C_(2)S and C_(3)S.Additionally,the column densities of both molecules are found to be sensitive to the cosmic ray ionization rate at several radial positions,while variations in the C/O ratio have comparatively minimal impact on L1544.展开更多
We introduce a mock galaxy catalog built for the China Space Survey Telescope(CSST)extragalactic surveys using the primary runs of the Jiutian N-body simulation suites.The catalogs are built by coupling the galaxy evo...We introduce a mock galaxy catalog built for the China Space Survey Telescope(CSST)extragalactic surveys using the primary runs of the Jiutian N-body simulation suites.The catalogs are built by coupling the galaxy evolution and assembly(GAe A)semianalytical model of galaxy formation with merger trees extracted from the simulations using the hierarchical bound-tracing(hb T+)algorithm.The spectral energy distributions(SEDs)and broadband magnitudes are computed using the neural-network-based stellar population synthesizer STARDus Te R,which is trained on radiative transfer simulations to account for detailed galaxy geometry in modeling dust obscuration.Galaxy light-cones up to z=5 are subsequently generated with the BLic light-cone builder,which interpolates the properties of galaxies over time using an optimized interpolation scheme.The resulting catalogs exhibit good convergence in many statistical properties of the galaxy population produced from two different resolution simulations.The catalogs reproduce a number of observed galaxy properties across a range of galaxy mass and redshift,including the stellar mass functions,the luminosity function,gas mass fraction,galaxy size-mass relation,and galaxy clustering.We also present the photometric and redshift distributions of galaxies expected to be observed in the CSST surveys.展开更多
Possible periodic features in fast radio bursts(FRBs)may provide insights into their astrophysical origins.Using extensive observations from the five-hundred-meter aperture spherical radio telescope(FAST),we conduct a...Possible periodic features in fast radio bursts(FRBs)may provide insights into their astrophysical origins.Using extensive observations from the five-hundred-meter aperture spherical radio telescope(FAST),we conduct a multi-timescale periodicity search for the exceptionally active repeater FRB 20240114A.Our analysis is based on different datasets for different timescales:for short-timescale periodicity in time of arrivals(TOAs),we use 57 observations from January to August 2024;for long-timescale periodicity,we employ an extended TOA dataset comprising 111 observations spanning from January 2024 to October 2025;and for burst time series analysis,we utilize individual burst data from the 57 FAST observations.We identify three candidate short-timescale periodic signals(0.673,0.635,and 0.536 s)with significances of 3.2σ-6σ,each detected in two independent observations.On longer timescales,we detect a significant(143.40±7.19)-d periodicity with 5.2σsignificance,establishing FRB 20240114A as a periodic repeater.In burst time series,we find quasi-periodic oscillations in the few hundred Hz range(3.4σand 3.7σ)and periodic burst trains with periods of several to tens of milliseconds(3σ-3.9σ),though these periodic features appear transient and short-lived.The detection of periodic signals at these different timescales indicates that FRB 20240114A exhibits intriguing periodic self-similar characteristics.Despite the comprehensive dataset,no definitive periodicity linked to the source's rotation is confirmed,placing stringent constraints on the intrinsic source properties and the modulation mechanisms.All data are available via the Science Data Bank.This paper is organized as follows.In sect.2,we search for periodic signals in the time-of-arrival(TOA)data of FRB 20240114A to explore possible links to magnetar rotation,binary orbits,and precession scenarios.In sect.3,we mainly investigate QPOs in the burst time series,which provide crucial insights into the underlying radiation mechanisms.Sect.4 discusses the implications of our findings,and sect.5 summarizes the main conclusions of this study.展开更多
The Chinese Space Station Survey Telescope(CSST)is a flagship space mission,supported by the China Manned Space Project,designed to carry out a large-area sky survey to explore the nature of dark matter and dark energ...The Chinese Space Station Survey Telescope(CSST)is a flagship space mission,supported by the China Manned Space Project,designed to carry out a large-area sky survey to explore the nature of dark matter and dark energy in the Universe.The onboard multi-band imaging and slitless spectroscopic modules will enable us to obtain photometric data for billions of galaxies and stars,as well as hundreds of millions of spectroscopic measurements,advancing various scientific analyses such as galaxy clustering and weak gravitational lensing.To support the image simulations for the main survey of the CSST mission,we present a mock catalog of stars and galaxies.For stars,the mock catalog is generated using either Galaxia or TRILEGAL,both of which provide a range of stellar properties to meet the requirements of CSST image simulations.For galaxies,we built a mock light-cone up to redshift z~3.5 from the cosmological N-body simulation and populated the mock galaxy catalog from the dark matter haloes using a semianalytical galaxy formation model.We then performed a full-sky ray-tracing simulation of weak gravitational lensing to obtain lensing shear at the position of each galaxy in the light-cone.To support both multi-band imaging and slitless spectroscopic simulations,we computed the spectral energy distribution(SED)for each galaxy based on its star formation history using a supervised deep learning model and determined the magnitudes in each band using the CSST throughputs.Finally,the properties of our mock galaxies include positions,redshifts,stellar masses,shapes,sizes,SEDs,lensing shears and magnifications.We have validated our mock catalog against observational data and theoretical models,with results showing good overall agreement.The catalog provides a flexible data set for the development of CSST image processing and can support a wide range of cosmological analyses within the CSST mission.展开更多
The Submillimeter Wave Astronomy Satellite(SWAS)was the first space telescope capable of high spectral resolution observations of terahertz spectral lines.We have investigated the integration ability of its two receiv...The Submillimeter Wave Astronomy Satellite(SWAS)was the first space telescope capable of high spectral resolution observations of terahertz spectral lines.We have investigated the integration ability of its two receivers and spectrometer during five and a half years of on-orbit operation.The CI,O_(2),H_(2)O,and^(13)CO spectra taken toward all observed Galactic sources were analyzed.The present results are based on spectra with a total integration time of up to 2.72×10~4hr(■10~8s).The noise in the spectra is generally consistent with that expected from the radiometer equation,without any sign of approaching a noise floor.This noise performance reflects the extremely stable performance of the passively cooled front end as well as other relevant components in the SWAS instrument throughout its mission lifetime.展开更多
We provide an overview of the Jiutian simulations,a hybrid simulation suite for the China space survey telescope(CSST)extragalactic surveys.It consists of four complementary modules:the primary runs with high resoluti...We provide an overview of the Jiutian simulations,a hybrid simulation suite for the China space survey telescope(CSST)extragalactic surveys.It consists of four complementary modules:the primary runs with high resolutions with the fiducial concordance cosmology,the emulator runs exploring the parameter uncertainties around the fiducial cosmology,the reconstruction runs intended for recovering the observed Universe position by position,and the extension runs employing extended cosmologies beyond the standard model.For the primary runs,two independent pipelines are adopted to construct subhaloes and merger trees.On top of them,four sets of mock galaxy light-cone catalogs are produced from semi-analytical models and subhalo abundance matching,providing a variety of observational properties including galaxy spectral energy distribution(SED),emission lines,lensing distortions,and mock images.The 129 emulator runs are used to train the CSST emulator,achieving one percent accuracy in predicting the matter power spectrum over k 10 h Mpc^(-1)and z 2.The reconstruction runs employ a number of subgrid baryonic models to predict the evolution and galaxy population resembling certain regions in the real Universe with constrained initial conditions,enabling controlled investigation of galaxy formation on top of structure formation.The extension runs cover models with warm dark matter,f(R)gravity,interacting dark energy,and nonzero neutrino masses,revealing differences in the cosmic structure under alternative cosmological models.We introduce the specifications for each run,the data products derived from them,the corresponding pipeline developments,and present some main tests.Using the primary runs,we also show that the subhalo peak mass functions of different levels are approximately universal.These simulations form a comprehensive and open simulation library for CSST surveys and beyond.展开更多
We report a constraint on the cosmological variation of the proton g-factor,g p.By comparing the measured redshifts between H_(I)21 cm and OH 18 cm lines observed with the newly commissioned Five-hundred-meter Apertur...We report a constraint on the cosmological variation of the proton g-factor,g p.By comparing the measured redshifts between H_(I)21 cm and OH 18 cm lines observed with the newly commissioned Five-hundred-meter Aperture Spherical radio Telescope(FAST)toward PKS 1413+135 at z=0.24671,we obtain Δg _(p)/g_(p)=(−4.3±2.5)×10^(−5),which is more than two orders of magnitude more sensitive than previous constraints.In addition,we obtain sensitive constraints ofΔ(μα^(2))/(μα^(2))=(2.0±1.2)×10^(−5) and Δ(μα^(2)g_(p)^(0.64))/(μα^(2)g_(p)^(0.64))=(−4.7±1.9)×10^(−6).展开更多
Fast radio bursts(FRBs)remain one of the most puzzling astrophysical phenomena.While most FRBs are detected only once or sporadically,we present the identification of FRB 20190520B as the first persistently active sou...Fast radio bursts(FRBs)remain one of the most puzzling astrophysical phenomena.While most FRBs are detected only once or sporadically,we present the identification of FRB 20190520B as the first persistently active source over a continuous span of~4 years.This rare long-term activity enabled a detailed investigation of its dispersion measure(DM)evolution.We also report that FRB 20190520B exhibits a substantial decrease in DM at a global rate of(-12.4±0.3)pc cm^(-3)yur^(-1),exceeding previous FRB’s DM variation measurements by a factor of three and surpassing those observed in pulsars by orders of magnitude.The magnitude and consistency of the DM evolution,along with a high host DM contribution,strongly indicate that the source resides in a dense,expanding ionized medium,likely a young supernova remnant(SNR).展开更多
The encounter desorption(ED)approach significantly deviates from the more rigorous microscopic Monte Carlo method when the surface H_(2)coverage is high.We propose an improved method that removes this limitation under...The encounter desorption(ED)approach significantly deviates from the more rigorous microscopic Monte Carlo method when the surface H_(2)coverage is high.We propose an improved method that removes this limitation under high H_(2)coverage.This method is applied to explain the coverage-dependent H_(2)desorption energy observed in experiments,E_(exptD2)(θ).Hydrogen molecules adsorbed on bare surfaces and those adsorbed on H_(2)substrates are distinguished and treated as different species,each characterized by distinct diffusion barriers and desorption energies.We find that the effective desorption energy calculated using the improved method shows much better agreement with E_(exptD2)(θ)than that obtained with the conventional ED approach.Moreover,the improved method clearly outperforms the original approach under conditions of high surface H_(2)coverage.展开更多
Theγ-ray emission from the W51 complex is widely acknowledged to be attributed to the interaction between the cosmic rays(CRs)accelerated by the shock of supernova remnant(SNR)W51C and the dense molecular clouds in t...Theγ-ray emission from the W51 complex is widely acknowledged to be attributed to the interaction between the cosmic rays(CRs)accelerated by the shock of supernova remnant(SNR)W51C and the dense molecular clouds in the adjacent star-forming region,W51B.However,the maximum acceleration capability of W51C for CRs remains elusive.Based on observations conducted with the Large High Altitude Air Shower Observatory(LHAASO),we report a significant detection ofγrays emanating from the W51 complex,with energies from 2 to 200 TeV.The LHAASO measurements,for the first time,extend theγ-ray emission from the W51 complex beyond 100 TeV and reveal a significant spectrum bending at tens of TeV.By combining the"π^(0)-decay bump"featured data from Fermi-LAT,the broadbandγ-ray spectrum of the W51 region can be well-characterized by a simple pp-collision model.The observed spectral bending feature suggests an exponential cutoff at~400 TeV or a power-law break at~200 TeV in the CR proton spectrum,most likely providing the first evidence of SNRs serving as CR accelerators approaching the PeV regime.Additionally,two young star clusters within W51B could also be theoretically viable to produce the most energeticγrays observed by LHAASO.Our findings strongly support the presence of extreme CR accelerators within the W51 complex and provide new insights into the origin of Galactic CRs.展开更多
Fast radio bursts(FRBs)are bright,millisecond-duration radio emissions originating from cosmological distances.In this study,we report multi-year polarization measurements of four repeating FRBs initially discovered b...Fast radio bursts(FRBs)are bright,millisecond-duration radio emissions originating from cosmological distances.In this study,we report multi-year polarization measurements of four repeating FRBs initially discovered by the Canadian Hydrogen Intensity Mapping Experiment(CHIME):FRBs 20190117A,20190208A,20190303A,and 20190417A.We observed the four repeating FRBs with the Five-hundred-meter Aperture Spherical Radio Telescope(FAST),detecting a total of 66 bursts.Two bursts from FRB 20190417A exhibit a circular polarization signal-to-noise ratio greater than 7,with the highest circular polarization fraction recorded at 35.7%.While the bursts from FRBs 20190208A and 20190303A are highly linearly polarized,those from FRBs 20190117A and 20190417A show depolarization due to multi-path propagation,with σ_(RM)=2.78±0.05and 5.19±0.09 rad m^(-2),respectively.The linear polarization distributions among five repeating FRBs—FRBs 20190208A,20190303A,20201124A,20220912A,and 20240114A—are nearly identical but show distinct differences from those of nonrepeating FRBs.FRBs 20190117A,20190303A,and 20190417A exhibit substantial rotation measure(RM)variations between bursts,joining other repeating FRBs in this behavior.Combining these findings with published results,64% of repeating FRBs show RM variations greater than 50 rad m^(-2),and 21% exhibit RM reversals.A significant proportion of repeating FRBs reside in a dynamic magneto-ionic environment.The structure function of RM variations shows a power-law index of γ~(0-0.8),corresponding to a shallow power spectrum α=-(γ+2)~-(2.0-2.8)of turbulence,if the RM variations are attributed to turbulence.This suggests that the variations are dominated by small-scale RM density fluctuations.We perform K-S tests to compare the RMs of repeating and non-repeating FRBs,which reveal a marginal dichotomy in the distribution of their RMs.We caution that the observed dichotomy may be due to the small sample size and selection biases.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
基金supported by the National Natural Science Foundation of China(NSFC,grant No.12220101003)the Leading Innovation and Entrepreneurship Team of Zhejiang Province of China(grant No.2023R01008)the National Key R&D Program of China No.2023YFE0110500。
文摘The axion,a leading dark matter(DM)candidate,can convert to photons in neutron star(NS)magnetospheres via the Primakoff effect,producing narrow-band radio emission that may be detected with high-sensitivity radio telescopes.Previous studies searched for axion DM-induced signals from the isolated NS J0806.4-4123 using observations of the Meer KAT UHF band(544–1088 MHz),but excluded the 1051–1088 MHz subband to mitigate potential sideband contamination.To probe this unexplored parameter space,we reprocessed the 1000–1088 MHz subband data using optimized radio frequency interference(RFI)flagging and meticulous sideband calibration.The flux stability of the calibrators and the consistency with Meer KAT’s system equivalent flux density confirmed the reliability of the data within the 1000–1080 MHz range,while the 1080–1088 MHz subband was omitted due to flux anomalies.No significant signals exceeding 5σsignificance were detected within the axion mass range of 4.136–4.467μe V(1000–1080 MHz),including the previously unprobed range 4.347–4.467μe V(1051–1080 MHz).Our null detection sets new stringent constraints with Meer KAT NS data,excluding axion-photon couplings|g_(aγγ)|?8.2×10^(-12)Ge V^(-1)at the 95%confidence level for DM masses between 4.347 and 4.467μe V.
基金supported by the National Natural Science Foundation of China(NSFC,Grant Nos.11988101,12203044,and 12473023)by the Leading Innovation and Entrepreneurship Team of Zhejiang Province of China grant No.2023R01008+2 种基金by Key R&D Program of Zhejiang grant No.2024SSYS0012by the University Annual Scientific Research Plan of Anhui Province(No.2023AH030052,No.2022AH010013)Cultivation Project for FAST Scientific Payoff and Research Achievement of CAMS-CAS。
文摘We present the first search for pulsed CH maser emission potentially stimulated by PSR J1644-4559,conducted using the ultra-wide-bandwidth low-frequency receiver on Murriyang,CSIRO's Parkes Radio Telescope.Observations targeted three CHΛ-doublet transitions at 3264,3335,and 3349 MHz,with a variability timescale of78 ms.We detected ten CH emission features at 3335 and 3349 MHz,and seven features at 3264 MHz,during both pulsar-ON and pulsar-OFF phases.The observed velocities align with the OH emission and absorption reported by a previous study,suggesting a close spatial association between CH and OH molecules.The derived column densities for CH clouds within the Parkes beam range from 0.05 to 9.8×10^(13)cm^(-2),indicating that these clouds are likely in diffuse and translucent states.Upper limits for CH column densities within the pulsar beam ranged from 0.3 to 9.8×10^(13)cm^(-2).Comparison of these column densities suggests that CH clouds may exhibit clumpiness and substructure.No significant stimulated emission feature was detected in the optical depth spectra.Additionally,as part of our search for pulsed stimulated emission,we investigated the potential CH absorption of the pulsar signal and found none,in agreement with astrophysical expectations.The upper limits for the potential maser amplification factors towards PSR J1644-4559 at 3264,3335,and 3349 MHz are 1.014,1.009,and 1.009,respectively.This study demonstrates the feasibility of detecting pulsed CH maser emission in the interstellar medium stimulated by pulsar photons.
基金supported by the National Natural Science Foundation of China(NSFC,Grant Nos.11988101 and12041302)the International Partnership Program of the Chinese Academy of Sciences(grant No.114A11KYSB20210010)+5 种基金National Key R&D Program of China No.2023YFA1608004operated by the California Institute of Technology under a contract with the National Aeronautics and Space Administration(80NM0018D0004)the support of the Tianchi Talent Program of Xinjiang Uygur Autonomous Regionthe Collaborative Research Center 1601(SFB 1601 sub-project A2)funded by the Deutsche Forschungsgemeinschaft—500700252support from the University of Cologne and its Global Faculty program。
文摘Molecular oxygen abundance is a key parameter in understanding the chemical network of the interstellar medium.We estimate the molecular oxygen column density and abundance for a sample of Galactic massive star formation regions based on observations from the Submillimiter Wave Astronomy Satellite(SWAS)survey.We obtained an averaged O_(2)spectrum based on this sample using the(SWAS)survey data(O_(2),487.249 GHz,N=3-1,J=3-2).No emission or absorption feature is seen around the supposed central velocity with a total integration time of t_(total)=8.67×10^(3)hr and an rms noise per channel of 1.45 m K.Assuming a kinetic temperature T_(kin)=30 K,we derive the 3σupper limit of the O_(2)column density to be 3.3×10^(15)cm^(-2),close to the lowest values reported in Galactic massive star formation regions in previous studies.The corresponding O_(2)abundance upper limit is6.7×10^(-8),lower than all previous results based on SWAS observations and is close to the lowest reported value in massive star formation regions.On a galactic scale,our statistical results confirm a generally low O_(2)abundance for Galactic massive star formation regions.This abundance is also lower than results reported in extragalactic sources.
基金supported by a grant from the National Natural Science Foundation of China(NSFC)No.11988101by the NSFC grant Nos.11703047,11773041,U2031119,12173052,12173053,12373032,and 11963002+6 种基金support from the China Postdoctoral Science Foundation grant No.2023M733271the Foundation of Education Bureau of Guizhou Province,China(grant No.KY(2020)003)supported by the International Partnership Program of the Chinese Academy of Sciences,program No.114A11KYSB20210010the Youth Innovation Promotion Association of the Chinese Academy of Sciences(ID Nos.2023064,2018075,and Y2022027)the support from the National Key R&D Program of China grant Nos.2022YFC2205202 and 2020SKA0120100supported by the CAS“Light of West China”Programthe support by the NSFC grant No.12373026。
文摘We used the Five-hundred-meter Aperture Spherical radio Telescope(FAST)to search for the molecular emissions in the L-band between 1.0 and 1.5 GHz toward four comets,C/2020 F3(NEOWISE),C/2020 R4(ATLAS),C/2021 A1(Leonard),and 67P/Churyumov-Gerasimenko during or after their perihelion passages.Thousands of molecular transition lines fall in this low-frequency range,many attributed to complex organic or prebiotic molecules.We conducted a blind search for the possible molecular lines in this frequency range in those comets and could not identify clear signals of molecular emissions in the data.Although several molecules have been detected at high frequencies of greater than100 GHz in comets,our results confirm that it is challenging to detect molecular transitions in the L-band frequency ranges.The non-detection of L-band molecular lines in the cometary environment could rule out the possibility of unusually strong lines,which could be caused by the masers or non-LTE effects.Although the line strengths are predicted to be weak,for FAST,using the ultra-wide bandwidth receiver and improving the radio frequency interference environments would enhance the detectability of those molecular transitions at low frequencies in the future.
基金the support from the Natural Science Foundation of Xinjiang Uygur Autonomous Region(Grant No.2024D01E37)the National Science Foundation of China(Grant No.12473025)+5 种基金funded by the National Natural Science Foundation of China(Grant Nos.12373026,12203091,12173075,and 11973076)the Xinjiang Tianchi Talent Program(2024)the support from the Xinjiang Tianchi Talent Program(2023)the Shanghai Natural Science Foundation(Grant No.22ZR1421400)the Natural Science Foundation of Xinjiang Uygur Autonomous Region(Grant No.2022D01A156)partially funded by the Regional Collaborative Innovation Project of Xin jiang Uyghur Autonomous Region(Grant No.2022E01050)。
文摘Sulfur-bearing species are widely utilized to investigate the physical structure of star-forming regions in interstellar media;however,the underlying sulfur chemistry in these environments remains poorly understood.Therefore,further studies of S-bearing species are fundamentally important,as they can enhance our understanding of the physical evolution of star-forming regions.This study presents observations of C_(2)S and C_(3)S in L1544,acquired using the Nanshan 26-m radio telescope,along with simulations of their chemical behavior using a one-dimensional physical model.The simulation results reveal significant radial variations in the column densities of C_(2)S and C_(3)S.Additionally,the column densities of both molecules are found to be sensitive to the cosmic ray ionization rate at several radial positions,while variations in the C/O ratio have comparatively minimal impact on L1544.
基金supported by the National Natural Science Foundation of China(Grant Nos.12595312,and 12573022)National Key R&D Program of China(Grant Nos.2023YFA1607800,2023YFA1607801,2023YFA1605600,and 2023YFA1605601)+10 种基金science research grants from the China Manned Space Project(Grant Nos.CMS-CSST-2021-A03,and CMS-CSST-2021-A02)111 project(Grant No.B20019)supported in part by Office of Science and Technology,Shanghai Municipal Government(Grant Nos.24DX1400100,and ZJ2023-ZD-001)the Yangyang Development Fundhas made use of the SVO Filter Profile Service“Carlos Rodrigo”,funded by MCIN/AEI/10.13039/501100011033/through grant PID2023-146210NBI00support from the Key R&D Program of Zhejiang,China(Grant No.2024SSYS0012)supported by the China Manned Space Program(Grant No.CMS-CSST-2025-A06)the National Natural Science Foundation of China(Grant No.12373009)the CAS Project for Young Scientists in Basic Research(Grant No.YSBR-062)the Fundamental Research Funds for the Central Universitiesthe Xiaomi Young Talents Program。
文摘We introduce a mock galaxy catalog built for the China Space Survey Telescope(CSST)extragalactic surveys using the primary runs of the Jiutian N-body simulation suites.The catalogs are built by coupling the galaxy evolution and assembly(GAe A)semianalytical model of galaxy formation with merger trees extracted from the simulations using the hierarchical bound-tracing(hb T+)algorithm.The spectral energy distributions(SEDs)and broadband magnitudes are computed using the neural-network-based stellar population synthesizer STARDus Te R,which is trained on radiative transfer simulations to account for detailed galaxy geometry in modeling dust obscuration.Galaxy light-cones up to z=5 are subsequently generated with the BLic light-cone builder,which interpolates the properties of galaxies over time using an optimized interpolation scheme.The resulting catalogs exhibit good convergence in many statistical properties of the galaxy population produced from two different resolution simulations.The catalogs reproduce a number of observed galaxy properties across a range of galaxy mass and redshift,including the stellar mass functions,the luminosity function,gas mass fraction,galaxy size-mass relation,and galaxy clustering.We also present the photometric and redshift distributions of galaxies expected to be observed in the CSST surveys.
基金supported by the National Natural Science Foundation of China(Grant Nos.12588202,12303042,12041303,12421003,12233002,12041306,12403100,W2442001,12203045,12447115,U2031117,and 12503050)supported by the International Partnership Program of Chinese Academy of Sciences(Grant No.114A11KYSB20210010)+10 种基金the National SKA Program of China(Grant Nos.2020SKA0120100,2020SKA0120200,and 2022SKA0130104)supported by the Youth Innovation Promotion Association CAS(Grant No.2021055)the CAS Youth Interdisciplinary Teamsupported by the National Key R&D Program of China(Grant Nos.2023YFE0110500 and QN2023061004L)supported by the Leading Innovation and Entrepreneurship Team of Zhejiang Province of China(Grant No.2023R01008)the support from the Xinjiang Tianchi Programsupported by the China Postdoctoral Science Foundation(Grant Nos.GZB20240308,2025T180875,and 2025M773199)supported by CAS Project(Grant No.JZHKYPT-2021-06)supported by the National Natural Science Foundation of China(Grant No.12503055)the Postdoctoral Fellowship Program of CPSF(Grant No.GZB2025073)supported by the CAS Project for Young Scientists in Basic Research(Grant No.YSBR-063)。
文摘Possible periodic features in fast radio bursts(FRBs)may provide insights into their astrophysical origins.Using extensive observations from the five-hundred-meter aperture spherical radio telescope(FAST),we conduct a multi-timescale periodicity search for the exceptionally active repeater FRB 20240114A.Our analysis is based on different datasets for different timescales:for short-timescale periodicity in time of arrivals(TOAs),we use 57 observations from January to August 2024;for long-timescale periodicity,we employ an extended TOA dataset comprising 111 observations spanning from January 2024 to October 2025;and for burst time series analysis,we utilize individual burst data from the 57 FAST observations.We identify three candidate short-timescale periodic signals(0.673,0.635,and 0.536 s)with significances of 3.2σ-6σ,each detected in two independent observations.On longer timescales,we detect a significant(143.40±7.19)-d periodicity with 5.2σsignificance,establishing FRB 20240114A as a periodic repeater.In burst time series,we find quasi-periodic oscillations in the few hundred Hz range(3.4σand 3.7σ)and periodic burst trains with periods of several to tens of milliseconds(3σ-3.9σ),though these periodic features appear transient and short-lived.The detection of periodic signals at these different timescales indicates that FRB 20240114A exhibits intriguing periodic self-similar characteristics.Despite the comprehensive dataset,no definitive periodicity linked to the source's rotation is confirmed,placing stringent constraints on the intrinsic source properties and the modulation mechanisms.All data are available via the Science Data Bank.This paper is organized as follows.In sect.2,we search for periodic signals in the time-of-arrival(TOA)data of FRB 20240114A to explore possible links to magnetar rotation,binary orbits,and precession scenarios.In sect.3,we mainly investigate QPOs in the burst time series,which provide crucial insights into the underlying radiation mechanisms.Sect.4 discusses the implications of our findings,and sect.5 summarizes the main conclusions of this study.
基金supported by the project of the CSST scientific data processing and analysis system of the China Manned Space Project supported by the National Natural Science Foundation of China(NSFC,No.11903082)the China Manned Space Program with grant Nos.CMS-CS ST-2025-A20,CMS-CSST-2025-A05 and CMSCSST-2021-A03+2 种基金support by the Natural Science Research Project of Anhui Educational Committee No.2024AH050049NSFC No.12003001the Anhui Project(Z010118169)。
文摘The Chinese Space Station Survey Telescope(CSST)is a flagship space mission,supported by the China Manned Space Project,designed to carry out a large-area sky survey to explore the nature of dark matter and dark energy in the Universe.The onboard multi-band imaging and slitless spectroscopic modules will enable us to obtain photometric data for billions of galaxies and stars,as well as hundreds of millions of spectroscopic measurements,advancing various scientific analyses such as galaxy clustering and weak gravitational lensing.To support the image simulations for the main survey of the CSST mission,we present a mock catalog of stars and galaxies.For stars,the mock catalog is generated using either Galaxia or TRILEGAL,both of which provide a range of stellar properties to meet the requirements of CSST image simulations.For galaxies,we built a mock light-cone up to redshift z~3.5 from the cosmological N-body simulation and populated the mock galaxy catalog from the dark matter haloes using a semianalytical galaxy formation model.We then performed a full-sky ray-tracing simulation of weak gravitational lensing to obtain lensing shear at the position of each galaxy in the light-cone.To support both multi-band imaging and slitless spectroscopic simulations,we computed the spectral energy distribution(SED)for each galaxy based on its star formation history using a supervised deep learning model and determined the magnitudes in each band using the CSST throughputs.Finally,the properties of our mock galaxies include positions,redshifts,stellar masses,shapes,sizes,SEDs,lensing shears and magnifications.We have validated our mock catalog against observational data and theoretical models,with results showing good overall agreement.The catalog provides a flexible data set for the development of CSST image processing and can support a wide range of cosmological analyses within the CSST mission.
文摘The Submillimeter Wave Astronomy Satellite(SWAS)was the first space telescope capable of high spectral resolution observations of terahertz spectral lines.We have investigated the integration ability of its two receivers and spectrometer during five and a half years of on-orbit operation.The CI,O_(2),H_(2)O,and^(13)CO spectra taken toward all observed Galactic sources were analyzed.The present results are based on spectra with a total integration time of up to 2.72×10~4hr(■10~8s).The noise in the spectra is generally consistent with that expected from the radiometer equation,without any sign of approaching a noise floor.This noise performance reflects the extremely stable performance of the passively cooled front end as well as other relevant components in the SWAS instrument throughout its mission lifetime.
基金supported by the China Manned Space Project(Grant No.CMS-CSST-2021-A03)the National Key R&D Program of China(Grant Nos.2023YFA1607800,and 2023YFA1607801)+2 种基金the Key R&D Program of Zhejiang,China(Grant No.2024SSYS0012)the National Natural Science Foundation of China(Grant No.12303005)the Shuimu Tsinghua Scholar Program(Grant No.2022SM173)。
文摘We provide an overview of the Jiutian simulations,a hybrid simulation suite for the China space survey telescope(CSST)extragalactic surveys.It consists of four complementary modules:the primary runs with high resolutions with the fiducial concordance cosmology,the emulator runs exploring the parameter uncertainties around the fiducial cosmology,the reconstruction runs intended for recovering the observed Universe position by position,and the extension runs employing extended cosmologies beyond the standard model.For the primary runs,two independent pipelines are adopted to construct subhaloes and merger trees.On top of them,four sets of mock galaxy light-cone catalogs are produced from semi-analytical models and subhalo abundance matching,providing a variety of observational properties including galaxy spectral energy distribution(SED),emission lines,lensing distortions,and mock images.The 129 emulator runs are used to train the CSST emulator,achieving one percent accuracy in predicting the matter power spectrum over k 10 h Mpc^(-1)and z 2.The reconstruction runs employ a number of subgrid baryonic models to predict the evolution and galaxy population resembling certain regions in the real Universe with constrained initial conditions,enabling controlled investigation of galaxy formation on top of structure formation.The extension runs cover models with warm dark matter,f(R)gravity,interacting dark energy,and nonzero neutrino masses,revealing differences in the cosmic structure under alternative cosmological models.We introduce the specifications for each run,the data products derived from them,the corresponding pipeline developments,and present some main tests.Using the primary runs,we also show that the subhalo peak mass functions of different levels are approximately universal.These simulations form a comprehensive and open simulation library for CSST surveys and beyond.
基金supported by the National Natural Science Foundation of China (Grant No.12588202)Renzhi Suceived the support from the National SKA Program of China (Grant No.2025SKA0130100)+5 种基金the Shanghai Super Postdoctoral Incentive Program (Grant No.2025322)the China Postdoctoral Science Foundation (Grant No.2025M783232)supported by the National Natural Science Foundation of China (Grant No.12473019)the Shanghai Pilot Program for Basic Research-Chinese Academy of Sciences,Shanghai Branch (Grant No.JCYJ-SHFY-2021-013)the National SKA Program of China (Grant No.2022SKA0120102)the China Manned Space Project (Grant No.CMSCSST-2025-A07)。
文摘We report a constraint on the cosmological variation of the proton g-factor,g p.By comparing the measured redshifts between H_(I)21 cm and OH 18 cm lines observed with the newly commissioned Five-hundred-meter Aperture Spherical radio Telescope(FAST)toward PKS 1413+135 at z=0.24671,we obtain Δg _(p)/g_(p)=(−4.3±2.5)×10^(−5),which is more than two orders of magnitude more sensitive than previous constraints.In addition,we obtain sensitive constraints ofΔ(μα^(2))/(μα^(2))=(2.0±1.2)×10^(−5) and Δ(μα^(2)g_(p)^(0.64))/(μα^(2)g_(p)^(0.64))=(−4.7±1.9)×10^(−6).
基金supported by the National Natural Science Foundation of China(12203069 and 12588202)support from the National SKA Program of China(2022SKA0130100)+5 种基金support from the Basic Research Project of Central China Normal University,the Hubei QB Project,the CAS Youth Interdisciplinary Team and the Foundation of Guizhou Provincial Education Department(KY(2023)059)supported by the National Natural Science Foundation of China(12473047)the National Key Research and Development Program of China(2024YFA1611603)supported by the National Natural Science Foundation of China(12203045)the Leading Innovation and Entrepreneurship Team of Zhejiang Province of China(2023R01008)the Key R D Program of Zhejiang Province(2024SSYS0012)。
文摘Fast radio bursts(FRBs)remain one of the most puzzling astrophysical phenomena.While most FRBs are detected only once or sporadically,we present the identification of FRB 20190520B as the first persistently active source over a continuous span of~4 years.This rare long-term activity enabled a detailed investigation of its dispersion measure(DM)evolution.We also report that FRB 20190520B exhibits a substantial decrease in DM at a global rate of(-12.4±0.3)pc cm^(-3)yur^(-1),exceeding previous FRB’s DM variation measurements by a factor of three and surpassing those observed in pulsars by orders of magnitude.The magnitude and consistency of the DM evolution,along with a high host DM contribution,strongly indicate that the source resides in a dense,expanding ionized medium,likely a young supernova remnant(SNR).
基金supported by the National Natural Science Foundation of China(No.12173023)。
文摘The encounter desorption(ED)approach significantly deviates from the more rigorous microscopic Monte Carlo method when the surface H_(2)coverage is high.We propose an improved method that removes this limitation under high H_(2)coverage.This method is applied to explain the coverage-dependent H_(2)desorption energy observed in experiments,E_(exptD2)(θ).Hydrogen molecules adsorbed on bare surfaces and those adsorbed on H_(2)substrates are distinguished and treated as different species,each characterized by distinct diffusion barriers and desorption energies.We find that the effective desorption energy calculated using the improved method shows much better agreement with E_(exptD2)(θ)than that obtained with the conventional ED approach.Moreover,the improved method clearly outperforms the original approach under conditions of high surface H_(2)coverage.
基金supported by the National Natural Science Foundation of China(12393851,12261160362,12393852,12393853,12393854,12022502,2205314,12105301,12105292,12105294,12005246,and 12173039)Department of Science and Technology of Sichuan Province(24NSFJQ0060 and 2024NSFSC0449)+5 种基金Project for Young Scientists in Basic Research of Chinese Academy of Sciences(YSBR-061,2022010)Thailand by the National Science and Technology Development Agency(NSTDA)National Research Council of Thailand(NRCT):High-Potential Research Team Grant Program(N42A650868)the Chengdu Management Committee of Tianfu New Area for constant financial support to research with LHAASO datathe Milky Way Imaging Scroll Painting(MWISP)project,sponsored by the National Key R&D Program of China(2023YFA1608000 and 2017YFA0402701)the CAS Key Research Program of Frontier Sciences(QYZDJ-SSW-SLH047)。
文摘Theγ-ray emission from the W51 complex is widely acknowledged to be attributed to the interaction between the cosmic rays(CRs)accelerated by the shock of supernova remnant(SNR)W51C and the dense molecular clouds in the adjacent star-forming region,W51B.However,the maximum acceleration capability of W51C for CRs remains elusive.Based on observations conducted with the Large High Altitude Air Shower Observatory(LHAASO),we report a significant detection ofγrays emanating from the W51 complex,with energies from 2 to 200 TeV.The LHAASO measurements,for the first time,extend theγ-ray emission from the W51 complex beyond 100 TeV and reveal a significant spectrum bending at tens of TeV.By combining the"π^(0)-decay bump"featured data from Fermi-LAT,the broadbandγ-ray spectrum of the W51 region can be well-characterized by a simple pp-collision model.The observed spectral bending feature suggests an exponential cutoff at~400 TeV or a power-law break at~200 TeV in the CR proton spectrum,most likely providing the first evidence of SNRs serving as CR accelerators approaching the PeV regime.Additionally,two young star clusters within W51B could also be theoretically viable to produce the most energeticγrays observed by LHAASO.Our findings strongly support the presence of extreme CR accelerators within the W51 complex and provide new insights into the origin of Galactic CRs.
基金supported by the National Natural Science Foundation of China(Grant Nos.12588202,12203045,12233002,12403100,12103069,and 12403042)the Leading Innovation and Entrepreneurship Team of Zhejiang Province of China(Grant No.2023R01008)+3 种基金the Key R&D Program of Zhejiang(Grant No.2024SSYS0012)supported by the National Natural Science Foundation of China(Grant No.12473047)the National SKA Program of China(Grant No.2022SKA0130100)the support from the Xinjiang Tianchi Program。
文摘Fast radio bursts(FRBs)are bright,millisecond-duration radio emissions originating from cosmological distances.In this study,we report multi-year polarization measurements of four repeating FRBs initially discovered by the Canadian Hydrogen Intensity Mapping Experiment(CHIME):FRBs 20190117A,20190208A,20190303A,and 20190417A.We observed the four repeating FRBs with the Five-hundred-meter Aperture Spherical Radio Telescope(FAST),detecting a total of 66 bursts.Two bursts from FRB 20190417A exhibit a circular polarization signal-to-noise ratio greater than 7,with the highest circular polarization fraction recorded at 35.7%.While the bursts from FRBs 20190208A and 20190303A are highly linearly polarized,those from FRBs 20190117A and 20190417A show depolarization due to multi-path propagation,with σ_(RM)=2.78±0.05and 5.19±0.09 rad m^(-2),respectively.The linear polarization distributions among five repeating FRBs—FRBs 20190208A,20190303A,20201124A,20220912A,and 20240114A—are nearly identical but show distinct differences from those of nonrepeating FRBs.FRBs 20190117A,20190303A,and 20190417A exhibit substantial rotation measure(RM)variations between bursts,joining other repeating FRBs in this behavior.Combining these findings with published results,64% of repeating FRBs show RM variations greater than 50 rad m^(-2),and 21% exhibit RM reversals.A significant proportion of repeating FRBs reside in a dynamic magneto-ionic environment.The structure function of RM variations shows a power-law index of γ~(0-0.8),corresponding to a shallow power spectrum α=-(γ+2)~-(2.0-2.8)of turbulence,if the RM variations are attributed to turbulence.This suggests that the variations are dominated by small-scale RM density fluctuations.We perform K-S tests to compare the RMs of repeating and non-repeating FRBs,which reveal a marginal dichotomy in the distribution of their RMs.We caution that the observed dichotomy may be due to the small sample size and selection biases.
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.
