The FAST radio telescope has significantly better sensitivity than any other current radio telescope.Consequently,FAST has discovered over a thousand new pulsars in sky regions already searched for 50 yr.The Galactic ...The FAST radio telescope has significantly better sensitivity than any other current radio telescope.Consequently,FAST has discovered over a thousand new pulsars in sky regions already searched for 50 yr.The Galactic Plane Pulsar Snapshot(GPPS)survey found three-quarters of these new pulsars.The article by Han et al.(2025)details the latest batch of 473 discoveries,bringing the total to 751.展开更多
We derive the gravitational-wave(GW)strain upper limits from resolvable supermassive black-hole binaries using the data from the Five-hundred-meter Aperture Spherical radio Telescope,in the context of the Chinese Puls...We derive the gravitational-wave(GW)strain upper limits from resolvable supermassive black-hole binaries using the data from the Five-hundred-meter Aperture Spherical radio Telescope,in the context of the Chinese Pulsar Timing Array project.We focus on circular orbits in theμHz GW frequency band between 10^(−7)and 3×10^(−6)Hz.This frequency band is higher than the traditional pulsar timing array band and is less explored.We used the data of the millisecond pulsar PSR J1713+5307 observed between 2019 August and 2021 April.A dense observation campaign was carried out in 2020 September to allow for theμHz band coverage.Our sky-averaged continuous source upper limit at the 95%confidence level at 1μHz is 1.26×10^(−12),while the same limit in the direction of the pulsar is 4.77×10^(−13).展开更多
Pulsar candidate identification is an indispensable task in pulsar science.Based on the characteristics of imbalanced and diverse pulsar data sets,and the lack of a unified processing framework,we first used dimension...Pulsar candidate identification is an indispensable task in pulsar science.Based on the characteristics of imbalanced and diverse pulsar data sets,and the lack of a unified processing framework,we first used dimensionality reduction and visualization to analyze potential deficiencies caused by the incompleteness of current data set extraction methods.We found that the limited use of non-pulsar data may lead to bias in the result,which may limit the generalization ability.Based on the dimensionality reduction results,we propose a Grid Group Uniform Sampling(GGUS) method.This data preprocessing method improves the performance of Random Forest,Support Vector Machine,Convolutional Neural Network,and Res Net50 models on Lyon’s features,diagnostic plots,and perioddispersion measure (period-DM) plots in the HTRU1 data set.The average recall increased by approximately0.5%,precision by nearly 2%,and F_(1) score by around 1.2%for all models and in all data sets.In the period-DM plots testing,the high-performance Res Net50 algorithm achieved over 98%F_(1) using random sampling.GGUS demonstrated further improvements in this test,enhancing the average F_(1) score,precision,and recall by approximately 0.07%,0.1%,and 0.03%,respectively.展开更多
A group of Chinese astronomers detected a weird pulsar that keeps emitting radio beams in long,regular pauses.After years of follow-up observations and careful data analyses,they finally revealed this exotic pulsar in...A group of Chinese astronomers detected a weird pulsar that keeps emitting radio beams in long,regular pauses.After years of follow-up observations and careful data analyses,they finally revealed this exotic pulsar in Science on May 23 as a rare case:it turns out to be eclipsed by a companion,very likely a helium star,with a mass similar to the Sun and in an orbit smaller than the solar radius.展开更多
The Five-hundred-meter Aperture Spherical Telescope(FAST)is living up to its promise as one of the world's premiere pulsar finding instruments.At the center of FAST's many significant pulsar discoveries(which ...The Five-hundred-meter Aperture Spherical Telescope(FAST)is living up to its promise as one of the world's premiere pulsar finding instruments.At the center of FAST's many significant pulsar discoveries(which in total number 1000 from all projects to date)is the announcement by Han et al.(2025)of a further 473 pulsars.The new discoveries are the latest installment from the FAST Galactic Plane Snapshot Survey(GPPS),bringing its total to 751 pulsars.Full details of the design and observational setup of the FAST GPPS can be found in Han et al.(2021).展开更多
Previous studies aiming to accelerate data processing have focused on enhancement algorithms,using the graphics processing unit(GPU)to speed up programs,and thread-level parallelism.These methods overlook maximizing t...Previous studies aiming to accelerate data processing have focused on enhancement algorithms,using the graphics processing unit(GPU)to speed up programs,and thread-level parallelism.These methods overlook maximizing the utilization of existing central processing unit(CPU)resources and reducing human and computational time costs via process automation.Accordingly,this paper proposes a scheme,called SSM,that combines“Srun job submission mode”,“Sbatch job submission mode”,and“Monitor function”.The SSM scheme includes three main modules:data management,command management,and resource management.Its core innovations are command splitting and parallel execution.The results show that this method effectively improves CPU utilization and reduces the time required for data processing.In terms of CPU utilization,the average value of this scheme is 89%.In contrast,the average CPU utilizations of“Srun job submission mode”and“Sbatch job submission mode”are significantly lower,at 43%and 52%,respectively.In terms of the data-processing time,SSM testing on the Five-hundred-meter Aperture Spherical radio Telescope(FAST)data requires only 5.5 h,compared with 8 h in the“Srun job submission mode”and 14 h in the“Sbatch job submission mode”.In addition,tests on the FAST and Parkes datasets demonstrate the universality of the SSM scheme,which can process data from different telescopes.The compatibility of the SSM scheme for pulsar searches is verified using 2 days of observational data from the globular cluster M2,with the scheme successfully discovering all published pulsars in M2.展开更多
Megahertz-peaked spectra(MPS)pulsars are referred as cases whose radio spectra turn over around 100 MHz.We identified 53 MPS pulsars based on the spectral data from the literature,and statistically analyzed the spatia...Megahertz-peaked spectra(MPS)pulsars are referred as cases whose radio spectra turn over around 100 MHz.We identified 53 MPS pulsars based on the spectral data from the literature,and statistically analyzed the spatial location distribution,the magnetic field-period distribution,peak frequencies,spectral indices,and dispersion measures of these MPS pulsars.We found that there is a strong positive correlation between the dispersion measures and the peak frequencies of MPS pulsars,and negative correlations of the dispersion measures with spectral indices and the ages are also found.Such correlations suggest that the interstellar medium is an important factor that affects observational properties of MPS pulsars.展开更多
The traditional orbit determination method based on pulsar profile distortion can determine the six elements of the orbit.However,the estimation accuracies of these methods are limited and the computational load of a ...The traditional orbit determination method based on pulsar profile distortion can determine the six elements of the orbit.However,the estimation accuracies of these methods are limited and the computational load of a six-dimensional search is huge.To solve this problem,the differential-geometry-based Multi-dimensional Joint Position-Velocity Estimation(MJPVE)using Crab pulsar profile distortion is proposed in this paper.Firstly,through theoretical analysis,it is found that the pulsar profile distortion caused by the initial state error in some joint positionvelocity directions is very small.In other words,the accuracies of estimation in these directions are very low.Namely,the search dimension can be reduced,which in turn greatly reduces the computational load.Then,we construct the chi-squared function of the pulsar profile with respect to the estimation error in joint position-velocity direction and use differential geometry to find the joint position-velocity directions corresponding to different degrees of distortion.Finally,we utilize the grid search based on directory folding in these joint position-velocity directions corresponding to large degrees of distortion to obtain the joint position-velocity estimation.The experimental results show that compared with the grouping bi-chi-squared inversion method,MJPVE has high precision and extensive navigation information.展开更多
Finding pulsars in binaries is important for measurements of the masses of neutron stars(NSs),for tests of gravity theories,and for studies of star evolution.We are carrying out the Galactic Plane Pulsar Snapshot surv...Finding pulsars in binaries is important for measurements of the masses of neutron stars(NSs),for tests of gravity theories,and for studies of star evolution.We are carrying out the Galactic Plane Pulsar Snapshot survey(GPPS)by using the Five-hundred-meter Aperture Spherical radio Telescope(FAST).Here we present the Keplerian parameters for 116 newly discovered pulsars in the FAST GPPS survey and obtain timing solutions for 29 pulsars.Companions of these pulsars are He white dwarfs(WDs),CO/ONe WDs,NSs,main sequence stars and ultra light objects or even planets.Our observations uncover eclipses of eight binary systems.The optical counterpart for the companion of PSR J1908+1036 is identified.The Post-Keplerian parameter w for the double NS systems PSR J0528+3529 and J1844-0128 have been measured,with which the total masses of the binary systems are determined.展开更多
Binary millisecond pulsars with a massive white dwarf(WD)companion are intermediate-mass binary pulsars(IMBPs).They are formed via the Case BB Roche-lobe overflow evolution channel if they are in compact orbits with a...Binary millisecond pulsars with a massive white dwarf(WD)companion are intermediate-mass binary pulsars(IMBPs).They are formed via the Case BB Roche-lobe overflow evolution channel if they are in compact orbits with an orbital period of less than 1 day.They are fairly rare in the known pulsar population;only five such IMBPs have been discovered before,and one of them is in a globular cluster.Here we report six IMBPs in compact orbits:PSRs J0416+5201,J0520+3722,J1919+1341,J1943+2210,J1947+2304 and J2023+2853,discovered during the Galactic Plane Pulsar Snapshot survey by using the Five-hundred-meter Aperture Spherical radio Telescope,doubling the number of such IMBPs due to the high survey sensitivity in the short survey time of 5 minutes.Follow-up timing observations show that they all have either a CO WD or an ONeMg WD companion with a mass greater than about 0.8M_(⊙)in a very circular orbit with an eccentricity in the order of10^(−5).PSR J0416+5201 should be an ONeMg WD companion with a remarkable minimum mass of 1.28M_(⊙).These massive WD companions lead to a detectable Shapiro delay for PSRs J0416+5201,J0520+3722,J1943+2210,and J2023+2853,indicating that their orbits are highly inclined.From the measurement of the Shapiro delay,the pulsar mass of J1943+2210 was constrained to be 1.84^(+0.11)_(-0.09)M_(⊙),and that of PSR J2023+2853 to be 1.28^(+0.06)_(-0.05)M_(⊙).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
We present a polarization study of 25 globular cluster(GC)pulsars observed with the Five-hundred-meter Aperture Spherical radio Telescope(FAST),including 15 pro les measured for the rst time.The pulse width–period re...We present a polarization study of 25 globular cluster(GC)pulsars observed with the Five-hundred-meter Aperture Spherical radio Telescope(FAST),including 15 pro les measured for the rst time.The pulse width–period relationships for millisecond pulsars(MSPs)in GCs follow power-law indices of-0.268(W10)and-0.330(W50),consistent with normal pulsars.Only 20%of the sample exhibit clear S-shaped position angle curves-signi cantly fewer than in the normal pulsar population.Rotation Measures(RMs)for these pulsars suggest that GCs near the Galactic plane show higher RMs,in agreement with former studies.Polarization ratios were measured,with M53A showing the highest linear polarization(56%)and M15H the highest absolute circular polarization(37%).On average,GC pulsars exhibit lower circular(-1%)and absolute circular(11%)polarization compared to normal pulsars observed with Parkes(5%and 32%,respectively).However,their polarization distributions align with MSPs in the Galactic plane,suggesting GC environments do not drastically alter emission properties.展开更多
Recent observations by pulsar timing array collaborations have detected a stochastic common-spectrum signal, which may originate from scalar-induced gravitational waves generated by primordial curvature perturbations ...Recent observations by pulsar timing array collaborations have detected a stochastic common-spectrum signal, which may originate from scalar-induced gravitational waves generated by primordial curvature perturbations during inflation.Using the NANOGrav 15-year data set, we explore this hypothesis by constraining the primordial curvature power spectrum and reheating energy scale. We model the primordial power spectrum with a lognormal form and consider reheating with the equation of state parameter w = 1/6. Our Bayesian analysis reveals a narrow peak in the primordial power spectrum(the width of the spectrum △ < 0.05 at the 95% confidence level) and constrains the reheating temperature to be 0.03 GeV<T_(rh)<7.2 Ge V. The best-fit SIGW spectrum shows a characteristic turning point near f ~ 10^(-8.1)Hz, marking the transition from reheating to radiation domination, providing a unique probe of the properties of the early Universe.展开更多
Clock difference between the ensemble pulsar timescale(PT)and the International Atomic Time(TAI)PT-TAI derived from the International Pulsar Timing Array(IPTA)data set indicates a very similar variation trend with the...Clock difference between the ensemble pulsar timescale(PT)and the International Atomic Time(TAI)PT-TAI derived from the International Pulsar Timing Array(IPTA)data set indicates a very similar variation trend with the Terrestrial Time TT(BIPMXXXX)-TAI but PT has larger measurement error.In this paper,we discuss the smoothing method of PT using a combined smoothing filter and compare the results with that from other filters.The clock difference sequence between PT-TAI and the first time derivative series of the TT(BIPMXXXX)-TAI can be combined by a combined smoothing filter to yield two smooth curves tied by the constraints assuring that the latter is the derivative of the former.The ensemble pulsar time IPTA2016 with respect to TAI published by G.Hobbs et al.and first time derivative series of the TT(BIPM2017)-TAI with quadratic polynomial terms removed are processed by combined smoothing filter in order to demonstrate the properties of the smoothed results.How to correctly estimate two smoothing coefficients is described and the output results of the combined smoothing filter are analyzed.The results show that the combined smoothing method efficiently removes high frequency noises of two input data series and the smoothed data of the PT-TAI combine long term fractional frequency stability of the pulsar time and frequency accuracy of the terrestrial time.Fractional frequency stability analysis indicates that both short and medium time interval stability of the smoothed PT-TAI is improved while keeping its original long term frequency stability level.The combined smoothing filter is more suitable for smoothing observational pulsar timescale data than any filter that only performs smoothing of a single pulsar time series.The smoothed pulsar time by combined smoothing filter is a pulsar atomic time combined timescale.This kind of combined timescale can also be used as terrestrial time.展开更多
Magnetars are slowly rotating,highly magnetized young neutron stars that can show transient radio phenomena for radio pulses and fast radio bursts.We conducted radio observations from two magnetars SGR J1935+2154 and ...Magnetars are slowly rotating,highly magnetized young neutron stars that can show transient radio phenomena for radio pulses and fast radio bursts.We conducted radio observations from two magnetars SGR J1935+2154 and 3XMM J185246.6+003317 and a high-magnetic field pulsar PSR J1846-0258 using the Five-hundred-meter Aperture Spherical radio Telescope(FAST).We performed single pulse and periodicity searches and did not detect radio signals from them.From the piggyback data recorded by other FAST telescope beams when we observed the magnetar SGR 1935+2154,we serendipitously discovered a new radio pulsar,PSR J1935+2200.We carried out the follow-up observations and obtained the timing solution based on these new observations and the archive FAST data.PSR J1935+2200 is an isolated old pulsar,with a spin period of 0.91 s,a spin-period derivative of 9.19×10^(−15)s s^(−1),and a characteristic age of 1.57 Myr.It is a weak pulsar with a flux density of 9.8μJy at 1.25 GHz.Discovery of a new pulsar from the long FAST observations of 30 minutes implies that there may be more weak older pulsars in the Galactic disk to be discovered.展开更多
The Five-hundred-meter Aperture Spherical radio Telescope(FAST)is the most sensitive telescope at the L-band(1.0-1.5 GHz)and has been used to carry out the FAST Galactic Plane Pulsar Snapshot(GPPS)survey in the last 5...The Five-hundred-meter Aperture Spherical radio Telescope(FAST)is the most sensitive telescope at the L-band(1.0-1.5 GHz)and has been used to carry out the FAST Galactic Plane Pulsar Snapshot(GPPS)survey in the last 5 yr.Up to now,the survey has covered one-fourth of the planned areas within±10o from the Galactic plane visible by FAST,and discovered 751 pulsars.After the first publication of the discovery of 201 pulsars and one rotating radio transient(RRAT)in 2021 and 76 RRATs in 2023,here we report the discovery of 473 new pulsars from the FAST GPPS survey,including 137 new millisecond pulsars and 30 new RRATs.We find 34 millisecond pulsars discovered by the GPPS survey which can be timed with a precision better than 3μs by using FAST 15 minute observations and can be used for pulsar timing arrays.The GPPS survey has discovered eight pulsars with periods greater than 10 s including one with 29.77 s.The integrated profiles of pulsars and individual pulses of RRATs are presented.During the FAST GPPS survey,we also detected previously known pulsars and updated parameters for 52 pulsars.In addition,we discovered two fast radio bursts plus one probable case with high dispersion measures indicating their extragalactic origin.展开更多
Determining accurate pulsar timing model parameters is essential for establishing TT(PT),a realization of Terrestrial Time(TT)based on a pulsar timescale(PT).This study discusses the impact of different data spans on ...Determining accurate pulsar timing model parameters is essential for establishing TT(PT),a realization of Terrestrial Time(TT)based on a pulsar timescale(PT).This study discusses the impact of different data spans on the accuracy of pulsar timing model parameters when determining pulsar timing model parameters.Using observations of PSR J0437-4715,J1909-3744,J1713+0747,and J1744-1134 from the second data release of the International Pulsar Timing Array(IPTA II,Version A),we compare the accuracy of the timing model parameters determined by these observations with different data spans.The results show for PSR J0437-4715,J1713+0747,and J1909-3744,the amplitude fluctuations of rotational frequency remain within 10^(−15),10^(−14),and 10^(−14) Hz,respectively,when the data spans for determining pulsar timing model parameters exceed 13,14,and 6 yr.Additionally,the one-year accuracy of TT(PT)is crucial for its application in timekeeping.By comparing the frequency deviations of TT(PT)relative to TT(BIPM)under both ideal(k_(r))and actual(k_(p))conditions across different data spans,we find that when the data span reaches the duration above,the accuracy of TT(PT)surpasses that of TT(TAI)under ideal conditions,slightly inferior under actual conditions.This suggests with improved observational technologies,the accuracy of TT(PT)can be further enhanced.展开更多
We report the discovery of an isolated millisecond pulsar M15O(J2129+1210O)from the globular cluster M15(NGC 7078)with a period of 11.06686 ms and a dispersion measure of~67.44 cm^(-3)pc.Its spin period is so close to...We report the discovery of an isolated millisecond pulsar M15O(J2129+1210O)from the globular cluster M15(NGC 7078)with a period of 11.06686 ms and a dispersion measure of~67.44 cm^(-3)pc.Its spin period is so close to the 10th harmonic of the bright pulsar M15A(~11.06647 ms)that it was missed in a previous pulsar search.We suggest adding the spectrum in the pulsar candidate diagnostic plot to identify new signals near the harmonics.M15O has the first spin frequency derivative and the second spin frequency derivative,being 1.79191(5)×10^(-14)Hz s^(-1)and 3.3133(6)×10^(-23)Hz s^(-2),respectively.Its projected distance from the optical center of M15 is the closest among all the pulsars in M15.The origin can be something from the center of the massive and core-collapsed globular cluster M15.展开更多
We report the results of a search for radio pulsars in five supernova remnants(SNRs)with the FAST telescope.The observations were made using the 19-beam receiver in“snapshot”mode.The integration time for each pointi...We report the results of a search for radio pulsars in five supernova remnants(SNRs)with the FAST telescope.The observations were made using the 19-beam receiver in“snapshot”mode.The integration time for each pointing was 10 min.We discovered a new pulsar,PSR J1845–0306,which has a spin period of 983.6 ms and a dispersion measure of 444.6±2.0 cm^(−3)·pc,in observations of SNR G29.6+0.1.To judge the association between the pulsar and the SNR,further verification is needed.We also re-detected some known pulsars in the data from SNRs G29.6+0.1 and G29.7–0.3.No pulsars were detected in the observations of the other three SNRs.展开更多
Timing newly discovered pulsars requires gradually building up a timing model that connects observations taken days to months apart.This sometimes can be challenging when our initial knowledge of the pulsar’s positio...Timing newly discovered pulsars requires gradually building up a timing model that connects observations taken days to months apart.This sometimes can be challenging when our initial knowledge of the pulsar’s position is arcminutes off from its true position.Such a position error leads to significant arrival time shifts as a result of the Earth’s orbital motion.Traditional down-hill fitting timing algorithms become ineffective when our model predicts the wrong pulse rotations for our next observation.For some pulsars whose model prediction is not too far off,the correct rotation number could be found by trial-and-error methods.For the remaining challenging pulsars,a more generalized method is called for.This paper proposes a GPU-based algorithm that could exhaustively search a large area of trail positions for probable timing solutions.This could help find phase-connected timing solutions for new pulsars using brute force.展开更多
文摘The FAST radio telescope has significantly better sensitivity than any other current radio telescope.Consequently,FAST has discovered over a thousand new pulsars in sky regions already searched for 50 yr.The Galactic Plane Pulsar Snapshot(GPPS)survey found three-quarters of these new pulsars.The article by Han et al.(2025)details the latest batch of 473 discoveries,bringing the total to 751.
基金supported by the FAST Key projectsupported by the National SKA Program of China (2020SKA0120100)+4 种基金the National Natural Science Foundation of China (NSFC, Grant Nos. 12041303 and 12250410246)the CAS-MPG LEGACY projectfunding from the Max-Planck Partner Groupsupport from the XPLORER PRIZE and 20 yr long-term support from Dr. Guojun Qiaosupported by Major Science and Technology Program of Xinjiang Uygur Autonomous Region No. 2022A03013-4
文摘We derive the gravitational-wave(GW)strain upper limits from resolvable supermassive black-hole binaries using the data from the Five-hundred-meter Aperture Spherical radio Telescope,in the context of the Chinese Pulsar Timing Array project.We focus on circular orbits in theμHz GW frequency band between 10^(−7)and 3×10^(−6)Hz.This frequency band is higher than the traditional pulsar timing array band and is less explored.We used the data of the millisecond pulsar PSR J1713+5307 observed between 2019 August and 2021 April.A dense observation campaign was carried out in 2020 September to allow for theμHz band coverage.Our sky-averaged continuous source upper limit at the 95%confidence level at 1μHz is 1.26×10^(−12),while the same limit in the direction of the pulsar is 4.77×10^(−13).
基金supported by the National Key Research and Development Program of China under grant No.2018YFA0404603supported by the Operation,Maintenance and Upgrading Fund for Astronomical Telescopes and Facility Instruments,budgeted from the Ministry of Finance of China (MOF) and administered by the Chinese Academy of Sciences (CAS)。
文摘Pulsar candidate identification is an indispensable task in pulsar science.Based on the characteristics of imbalanced and diverse pulsar data sets,and the lack of a unified processing framework,we first used dimensionality reduction and visualization to analyze potential deficiencies caused by the incompleteness of current data set extraction methods.We found that the limited use of non-pulsar data may lead to bias in the result,which may limit the generalization ability.Based on the dimensionality reduction results,we propose a Grid Group Uniform Sampling(GGUS) method.This data preprocessing method improves the performance of Random Forest,Support Vector Machine,Convolutional Neural Network,and Res Net50 models on Lyon’s features,diagnostic plots,and perioddispersion measure (period-DM) plots in the HTRU1 data set.The average recall increased by approximately0.5%,precision by nearly 2%,and F_(1) score by around 1.2%for all models and in all data sets.In the period-DM plots testing,the high-performance Res Net50 algorithm achieved over 98%F_(1) using random sampling.GGUS demonstrated further improvements in this test,enhancing the average F_(1) score,precision,and recall by approximately 0.07%,0.1%,and 0.03%,respectively.
文摘A group of Chinese astronomers detected a weird pulsar that keeps emitting radio beams in long,regular pauses.After years of follow-up observations and careful data analyses,they finally revealed this exotic pulsar in Science on May 23 as a rare case:it turns out to be eclipsed by a companion,very likely a helium star,with a mass similar to the Sun and in an orbit smaller than the solar radius.
文摘The Five-hundred-meter Aperture Spherical Telescope(FAST)is living up to its promise as one of the world's premiere pulsar finding instruments.At the center of FAST's many significant pulsar discoveries(which in total number 1000 from all projects to date)is the announcement by Han et al.(2025)of a further 473 pulsars.The new discoveries are the latest installment from the FAST Galactic Plane Snapshot Survey(GPPS),bringing its total to 751 pulsars.Full details of the design and observational setup of the FAST GPPS can be found in Han et al.(2021).
基金supported by the National Nature Science Foundation of China(12363010)supported by the Guizhou Provincial Basic Research Program(Natural Science)(ZK[2023]039)the Key Technology R&D Program([2023]352).
文摘Previous studies aiming to accelerate data processing have focused on enhancement algorithms,using the graphics processing unit(GPU)to speed up programs,and thread-level parallelism.These methods overlook maximizing the utilization of existing central processing unit(CPU)resources and reducing human and computational time costs via process automation.Accordingly,this paper proposes a scheme,called SSM,that combines“Srun job submission mode”,“Sbatch job submission mode”,and“Monitor function”.The SSM scheme includes three main modules:data management,command management,and resource management.Its core innovations are command splitting and parallel execution.The results show that this method effectively improves CPU utilization and reduces the time required for data processing.In terms of CPU utilization,the average value of this scheme is 89%.In contrast,the average CPU utilizations of“Srun job submission mode”and“Sbatch job submission mode”are significantly lower,at 43%and 52%,respectively.In terms of the data-processing time,SSM testing on the Five-hundred-meter Aperture Spherical radio Telescope(FAST)data requires only 5.5 h,compared with 8 h in the“Srun job submission mode”and 14 h in the“Sbatch job submission mode”.In addition,tests on the FAST and Parkes datasets demonstrate the universality of the SSM scheme,which can process data from different telescopes.The compatibility of the SSM scheme for pulsar searches is verified using 2 days of observational data from the globular cluster M2,with the scheme successfully discovering all published pulsars in M2.
基金supported in part by Chunhui plan international cooperation project of China Education Ministry under grants 202201406 and HZKY20220171.
文摘Megahertz-peaked spectra(MPS)pulsars are referred as cases whose radio spectra turn over around 100 MHz.We identified 53 MPS pulsars based on the spectral data from the literature,and statistically analyzed the spatial location distribution,the magnetic field-period distribution,peak frequencies,spectral indices,and dispersion measures of these MPS pulsars.We found that there is a strong positive correlation between the dispersion measures and the peak frequencies of MPS pulsars,and negative correlations of the dispersion measures with spectral indices and the ages are also found.Such correlations suggest that the interstellar medium is an important factor that affects observational properties of MPS pulsars.
基金supported in part by the National Natural Science Foundation of China(Nos.61873196,62373030,61772187)the Innovation Program for Quantum Science and Technology(No.2021ZD0303400)。
文摘The traditional orbit determination method based on pulsar profile distortion can determine the six elements of the orbit.However,the estimation accuracies of these methods are limited and the computational load of a six-dimensional search is huge.To solve this problem,the differential-geometry-based Multi-dimensional Joint Position-Velocity Estimation(MJPVE)using Crab pulsar profile distortion is proposed in this paper.Firstly,through theoretical analysis,it is found that the pulsar profile distortion caused by the initial state error in some joint positionvelocity directions is very small.In other words,the accuracies of estimation in these directions are very low.Namely,the search dimension can be reduced,which in turn greatly reduces the computational load.Then,we construct the chi-squared function of the pulsar profile with respect to the estimation error in joint position-velocity direction and use differential geometry to find the joint position-velocity directions corresponding to different degrees of distortion.Finally,we utilize the grid search based on directory folding in these joint position-velocity directions corresponding to large degrees of distortion to obtain the joint position-velocity estimation.The experimental results show that compared with the grouping bi-chi-squared inversion method,MJPVE has high precision and extensive navigation information.
基金supported by the National SKA program of China(No.2020SKA0120200)the National Natural Science Foundation of China(No.12133004)+1 种基金the Chinese Academy of Science(No.JZHKYPT-2021-06)and the National Key R&D Program of China(No.2021YFA1600401 and 2021YFA1600400)supported by the National Natural Science Foundation of China(No.11988101,12133004 and 11833009).
文摘Finding pulsars in binaries is important for measurements of the masses of neutron stars(NSs),for tests of gravity theories,and for studies of star evolution.We are carrying out the Galactic Plane Pulsar Snapshot survey(GPPS)by using the Five-hundred-meter Aperture Spherical radio Telescope(FAST).Here we present the Keplerian parameters for 116 newly discovered pulsars in the FAST GPPS survey and obtain timing solutions for 29 pulsars.Companions of these pulsars are He white dwarfs(WDs),CO/ONe WDs,NSs,main sequence stars and ultra light objects or even planets.Our observations uncover eclipses of eight binary systems.The optical counterpart for the companion of PSR J1908+1036 is identified.The Post-Keplerian parameter w for the double NS systems PSR J0528+3529 and J1844-0128 have been measured,with which the total masses of the binary systems are determined.
基金supported by the National Natural Science Foundation of China(NSFC,Grant Nos.11988101,12133004 and 11833009)the Research Program of the Chinese Academy of Sciences(grant No.QYZDJ-SSW-SLH021 and JZHKYPT-2021-06).
文摘Binary millisecond pulsars with a massive white dwarf(WD)companion are intermediate-mass binary pulsars(IMBPs).They are formed via the Case BB Roche-lobe overflow evolution channel if they are in compact orbits with an orbital period of less than 1 day.They are fairly rare in the known pulsar population;only five such IMBPs have been discovered before,and one of them is in a globular cluster.Here we report six IMBPs in compact orbits:PSRs J0416+5201,J0520+3722,J1919+1341,J1943+2210,J1947+2304 and J2023+2853,discovered during the Galactic Plane Pulsar Snapshot survey by using the Five-hundred-meter Aperture Spherical radio Telescope,doubling the number of such IMBPs due to the high survey sensitivity in the short survey time of 5 minutes.Follow-up timing observations show that they all have either a CO WD or an ONeMg WD companion with a mass greater than about 0.8M_(⊙)in a very circular orbit with an eccentricity in the order of10^(−5).PSR J0416+5201 should be an ONeMg WD companion with a remarkable minimum mass of 1.28M_(⊙).These massive WD companions lead to a detectable Shapiro delay for PSRs J0416+5201,J0520+3722,J1943+2210,and J2023+2853,indicating that their orbits are highly inclined.From the measurement of the Shapiro delay,the pulsar mass of J1943+2210 was constrained to be 1.84^(+0.11)_(-0.09)M_(⊙),and that of PSR J2023+2853 to be 1.28^(+0.06)_(-0.05)M_(⊙).
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 Key R&D Program of China,No.2022YFC2205202the National Natural Science Foundation of China(NSFC)under grant Nos.12173052,U2031119,11773041 and 11703047+2 种基金supported by the Youth Innovation Promotion Association of the Chinese Academy of Sciences(CAS)(id.Y2022027)the CAS“Light of West China”Programthe CAS President’s International Fellowship Initiative(grant No.2021FSM0004).
文摘We present a polarization study of 25 globular cluster(GC)pulsars observed with the Five-hundred-meter Aperture Spherical radio Telescope(FAST),including 15 pro les measured for the rst time.The pulse width–period relationships for millisecond pulsars(MSPs)in GCs follow power-law indices of-0.268(W10)and-0.330(W50),consistent with normal pulsars.Only 20%of the sample exhibit clear S-shaped position angle curves-signi cantly fewer than in the normal pulsar population.Rotation Measures(RMs)for these pulsars suggest that GCs near the Galactic plane show higher RMs,in agreement with former studies.Polarization ratios were measured,with M53A showing the highest linear polarization(56%)and M15H the highest absolute circular polarization(37%).On average,GC pulsars exhibit lower circular(-1%)and absolute circular(11%)polarization compared to normal pulsars observed with Parkes(5%and 32%,respectively).However,their polarization distributions align with MSPs in the Galactic plane,suggesting GC environments do not drastically alter emission properties.
基金supported by the National Natural Science Foundation of China (Grant No. 12305059)supported by the National Natural Science Foundation of China (Grant No. 12305075)+3 种基金supported by the National Natural Science Foundation of China (Grant No. 12403002)the Joint Fund of Henan Province Science and Technology R&D Program (Grant No. 235200810111)the Startup Research Fund of Henan Academy of Sciences (Grant No. 241841224)the Startup Research Fund of Henan Academy of Sciences (Grant No. 241841221)。
文摘Recent observations by pulsar timing array collaborations have detected a stochastic common-spectrum signal, which may originate from scalar-induced gravitational waves generated by primordial curvature perturbations during inflation.Using the NANOGrav 15-year data set, we explore this hypothesis by constraining the primordial curvature power spectrum and reheating energy scale. We model the primordial power spectrum with a lognormal form and consider reheating with the equation of state parameter w = 1/6. Our Bayesian analysis reveals a narrow peak in the primordial power spectrum(the width of the spectrum △ < 0.05 at the 95% confidence level) and constrains the reheating temperature to be 0.03 GeV<T_(rh)<7.2 Ge V. The best-fit SIGW spectrum shows a characteristic turning point near f ~ 10^(-8.1)Hz, marking the transition from reheating to radiation domination, providing a unique probe of the properties of the early Universe.
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences(grant No.XDA0350502)the National SKA Program of China(grant No.2020SKA0120103)the National Natural Science Foundation of China(NSFC,Grant Nos.U1831130 and 11973046)。
文摘Clock difference between the ensemble pulsar timescale(PT)and the International Atomic Time(TAI)PT-TAI derived from the International Pulsar Timing Array(IPTA)data set indicates a very similar variation trend with the Terrestrial Time TT(BIPMXXXX)-TAI but PT has larger measurement error.In this paper,we discuss the smoothing method of PT using a combined smoothing filter and compare the results with that from other filters.The clock difference sequence between PT-TAI and the first time derivative series of the TT(BIPMXXXX)-TAI can be combined by a combined smoothing filter to yield two smooth curves tied by the constraints assuring that the latter is the derivative of the former.The ensemble pulsar time IPTA2016 with respect to TAI published by G.Hobbs et al.and first time derivative series of the TT(BIPM2017)-TAI with quadratic polynomial terms removed are processed by combined smoothing filter in order to demonstrate the properties of the smoothed results.How to correctly estimate two smoothing coefficients is described and the output results of the combined smoothing filter are analyzed.The results show that the combined smoothing method efficiently removes high frequency noises of two input data series and the smoothed data of the PT-TAI combine long term fractional frequency stability of the pulsar time and frequency accuracy of the terrestrial time.Fractional frequency stability analysis indicates that both short and medium time interval stability of the smoothed PT-TAI is improved while keeping its original long term frequency stability level.The combined smoothing filter is more suitable for smoothing observational pulsar timescale data than any filter that only performs smoothing of a single pulsar time series.The smoothed pulsar time by combined smoothing filter is a pulsar atomic time combined timescale.This kind of combined timescale can also be used as terrestrial time.
基金supported by the National Natural Science Foundation of China:Nos.11988101,and 11833009also the National SKA Program of China 2020SKA0120100.
文摘Magnetars are slowly rotating,highly magnetized young neutron stars that can show transient radio phenomena for radio pulses and fast radio bursts.We conducted radio observations from two magnetars SGR J1935+2154 and 3XMM J185246.6+003317 and a high-magnetic field pulsar PSR J1846-0258 using the Five-hundred-meter Aperture Spherical radio Telescope(FAST).We performed single pulse and periodicity searches and did not detect radio signals from them.From the piggyback data recorded by other FAST telescope beams when we observed the magnetar SGR 1935+2154,we serendipitously discovered a new radio pulsar,PSR J1935+2200.We carried out the follow-up observations and obtained the timing solution based on these new observations and the archive FAST data.PSR J1935+2200 is an isolated old pulsar,with a spin period of 0.91 s,a spin-period derivative of 9.19×10^(−15)s s^(−1),and a characteristic age of 1.57 Myr.It is a weak pulsar with a flux density of 9.8μJy at 1.25 GHz.Discovery of a new pulsar from the long FAST observations of 30 minutes implies that there may be more weak older pulsars in the Galactic disk to be discovered.
基金supported by the National Natural Science Foundation of China(NSFC,Grant Nos.11988101,12133004 and 11833009)also the National SKA Program of China 2020SKA0120100The pulsar searching team is specially supported by the Chinese Academy of Sciences via the project JZHKYPT-2021-06.
文摘The Five-hundred-meter Aperture Spherical radio Telescope(FAST)is the most sensitive telescope at the L-band(1.0-1.5 GHz)and has been used to carry out the FAST Galactic Plane Pulsar Snapshot(GPPS)survey in the last 5 yr.Up to now,the survey has covered one-fourth of the planned areas within±10o from the Galactic plane visible by FAST,and discovered 751 pulsars.After the first publication of the discovery of 201 pulsars and one rotating radio transient(RRAT)in 2021 and 76 RRATs in 2023,here we report the discovery of 473 new pulsars from the FAST GPPS survey,including 137 new millisecond pulsars and 30 new RRATs.We find 34 millisecond pulsars discovered by the GPPS survey which can be timed with a precision better than 3μs by using FAST 15 minute observations and can be used for pulsar timing arrays.The GPPS survey has discovered eight pulsars with periods greater than 10 s including one with 29.77 s.The integrated profiles of pulsars and individual pulses of RRATs are presented.During the FAST GPPS survey,we also detected previously known pulsars and updated parameters for 52 pulsars.In addition,we discovered two fast radio bursts plus one probable case with high dispersion measures indicating their extragalactic origin.
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences(grant No.XDA0350502)the National SKA Program of China(No.2020SKA0120103)the National Natural Science Foundation of China(No.U1831130).
文摘Determining accurate pulsar timing model parameters is essential for establishing TT(PT),a realization of Terrestrial Time(TT)based on a pulsar timescale(PT).This study discusses the impact of different data spans on the accuracy of pulsar timing model parameters when determining pulsar timing model parameters.Using observations of PSR J0437-4715,J1909-3744,J1713+0747,and J1744-1134 from the second data release of the International Pulsar Timing Array(IPTA II,Version A),we compare the accuracy of the timing model parameters determined by these observations with different data spans.The results show for PSR J0437-4715,J1713+0747,and J1909-3744,the amplitude fluctuations of rotational frequency remain within 10^(−15),10^(−14),and 10^(−14) Hz,respectively,when the data spans for determining pulsar timing model parameters exceed 13,14,and 6 yr.Additionally,the one-year accuracy of TT(PT)is crucial for its application in timekeeping.By comparing the frequency deviations of TT(PT)relative to TT(BIPM)under both ideal(k_(r))and actual(k_(p))conditions across different data spans,we find that when the data span reaches the duration above,the accuracy of TT(PT)surpasses that of TT(TAI)under ideal conditions,slightly inferior under actual conditions.This suggests with improved observational technologies,the accuracy of TT(PT)can be further enhanced.
基金supported by the National Key R&D Program of China No.2022YFC2205202,No.2020SKA0120100the National Natural Science Foundation of China(NSFC,grant Nos.12373032,12003047,11773041,U2031119,12173052,and 12173053)+2 种基金supported by the Youth Innovation Promotion Association of CAS(id.2018075,Y2022027 and 2023064)the CAS“Light of West China”Programsupported by the Science and Technology Program of Guizhou Province under project No.QKHPTRC-ZDSYS[2023]003 and QKHFQ[2023]003。
文摘We report the discovery of an isolated millisecond pulsar M15O(J2129+1210O)from the globular cluster M15(NGC 7078)with a period of 11.06686 ms and a dispersion measure of~67.44 cm^(-3)pc.Its spin period is so close to the 10th harmonic of the bright pulsar M15A(~11.06647 ms)that it was missed in a previous pulsar search.We suggest adding the spectrum in the pulsar candidate diagnostic plot to identify new signals near the harmonics.M15O has the first spin frequency derivative and the second spin frequency derivative,being 1.79191(5)×10^(-14)Hz s^(-1)and 3.3133(6)×10^(-23)Hz s^(-2),respectively.Its projected distance from the optical center of M15 is the closest among all the pulsars in M15.The origin can be something from the center of the massive and core-collapsed globular cluster M15.
基金supported by the National SKA Program of China (Grant No. 2020SKA0120200)the National Natural Science Foundation of China (Grant Nos. 12041303, 12273100, 12041304, and 12288102)+5 种基金the National Key R&D Program of China (Grant No. 2022YFC2205201)the West Light Foundation of the Chinese Academy of Sciences (Grant No. WLFC 2021-XBQNXZ-027)the Major Science and Technology Program of Xinjiang Uygur Autonomous Region (Grant No. 2022A03013-4)the Natural Science Foundation of Xinjiiang Uygur Autonomous Region (Grant No. 2022D01D85)the open program of the Key Laboratory of Xinjiang Uygur Autonomous Region (Grant No. 2020D04049)partly supported by the Operation, Maintenance and Upgrading Fund for Astronomical Telescopes and Facility Instruments, budgeted from the Ministry of Finance of China and administrated by the CAS
文摘We report the results of a search for radio pulsars in five supernova remnants(SNRs)with the FAST telescope.The observations were made using the 19-beam receiver in“snapshot”mode.The integration time for each pointing was 10 min.We discovered a new pulsar,PSR J1845–0306,which has a spin period of 983.6 ms and a dispersion measure of 444.6±2.0 cm^(−3)·pc,in observations of SNR G29.6+0.1.To judge the association between the pulsar and the SNR,further verification is needed.We also re-detected some known pulsars in the data from SNRs G29.6+0.1 and G29.7–0.3.No pulsars were detected in the observations of the other three SNRs.
基金supported by the National Natural Science Foundation of China(12041303)the National SKA Program of China(2020SKA0120200)+2 种基金the CAS Project for Young Scientists in Basic Research YSBR-063the National Natural Science Foundation of China(NSFC grant Nos.12203070 and Nos.12203072)the CAS-MPG LEGACY project。
文摘Timing newly discovered pulsars requires gradually building up a timing model that connects observations taken days to months apart.This sometimes can be challenging when our initial knowledge of the pulsar’s position is arcminutes off from its true position.Such a position error leads to significant arrival time shifts as a result of the Earth’s orbital motion.Traditional down-hill fitting timing algorithms become ineffective when our model predicts the wrong pulse rotations for our next observation.For some pulsars whose model prediction is not too far off,the correct rotation number could be found by trial-and-error methods.For the remaining challenging pulsars,a more generalized method is called for.This paper proposes a GPU-based algorithm that could exhaustively search a large area of trail positions for probable timing solutions.This could help find phase-connected timing solutions for new pulsars using brute force.
