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
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
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
SN 2014av is a type Ibn supernova(SN)characterized by the interaction between the SN ejecta and a helium-rich circumstellar medium(CSM).We use the^(56)Ni model,the ejecta-CSM interaction(CSI)model,and the CSI plus^(56...SN 2014av is a type Ibn supernova(SN)characterized by the interaction between the SN ejecta and a helium-rich circumstellar medium(CSM).We use the^(56)Ni model,the ejecta-CSM interaction(CSI)model,and the CSI plus^(56)Ni model to fit the multiband light curves(LCs)of SN 2014av.For the CSI and CSI plus^(56)Ni models,we assume that the CSM is a constant density shell(“shell”)or a steady-state stellar wind(“wind”)with density∝r-2.We find that both the^(56)Ni and CSI models fail to fit the multiband LCs of SN 2014av,while the CSI plus^(56)Ni model can account for the LCs.In the last scenario,the LCs around the peaks were mainly powered by the CSI,while the flattening of the LCs was mainly powered by the radioactive decay of^(56)Ni.For the wind case,the derived mass-loss rate of the progenitor is≈20.5-205.5 M_(⊙)yr^(-1),whose lower limit is significantly larger than the upper limit of normal stellar winds,and comparable the upper limit of hyper-winds.Hence,we suggest that the wind case is disfavored.For the shell case,the best-fitting values of the ejecta,^(56)Ni,and the CSM are2.29 M_(⊙),0.09 M_(⊙),and 5.00 M_(⊙),respectively.Provided the velocity of the CSM shell is 100-1000 km s^(-1),we infer that the shell might be expelled≈0.49-5.20 yr before the SN exploded.展开更多
In this paper,we determine the photosphere evolution of PTF11rka which is a type Ic supernova (SN) by fitting its spectral energy distributions at different epochs.We find that the photosphere of PTF11rka expanded at ...In this paper,we determine the photosphere evolution of PTF11rka which is a type Ic supernova (SN) by fitting its spectral energy distributions at different epochs.We find that the photosphere of PTF11rka expanded at a constant velocity at early epochs,and the photosphere temperature increased slightly after reaching a minimum.These features are reminiscent of those of SN 2017dio.Based on the photosphere module that can describe the photosphere evolution of PTF11rka,we use the ^(56)Ni cascade decay model to fit its multiband light curves (LCs),finding that the model can well fit the photometric data.The derived ejecta mass and ^(56)Ni mass are respectively 8.76■ and 0.29-0.41■;the derived peak luminosity and the rise time of the theoretical bolometric LC of PTF11rka are ~8.24×10^(42)erg s^(-1) and ~35 days,respectively.Moreover,we find that the theoretical multiband LCs and the theoretical bolometric LC of PTF11rka do not show early-time excesses proposed in the literature.This indicates that additional energy sources (e.g.,the interaction between the ejecta and the circumstellar material)suggested to be responsible for the early-time excess can be neglected.展开更多
Early multiwavelength observations offer crucial insights into the nature of the relativistic jets responsible for gamma-ray bursts and their interaction with the surrounding medium.We present data of GRB 240825A from...Early multiwavelength observations offer crucial insights into the nature of the relativistic jets responsible for gamma-ray bursts and their interaction with the surrounding medium.We present data of GRB 240825A from 17 space-and ground-based telescopes/instruments,covering wavelengths from NIR/optical to X-ray and GeV,and spanning from the prompt emission to the afterglow phase triggered by Swift and Fermi.The early afterglow observations were carried out by SVOM/C-GFT,and spectroscopic observations of the afterglow by GTC,VLT,and TNG determined the redshift of the burst(z=0.659)later.A comprehensive analysis of the prompt emission spectrum observed by Swift-BAT and Fermi-GBM/LAT reveals a rare and significant high-energy cutoff at 76 MeV.Assuming this cutoff is due toγγabsorption allows us to place an upper limit on the initial Lorentz factor,Γ_(0)<245.The optical/NIR and GeV afterglow light curves can be described by the standard external shock model,with early-time emission dominated by a reverse shock(RS)and a subsequent transition to forward shock(FS)emission.Our afterglow modeling yields a consistent estimate of the initial Lorentz factor(Γ_(0)∼234).Furthermore,the RS-to-FS magnetic field ratio(R 302B)indicates that the RS region is significantly more magnetized than the FS region.An isotropic-equivalent kinetic energy of E_(k,iso)=5.25×10^(54) erg is derived,and the correspondingγ-ray radiation efficiency is estimated to beη_(γ)=3.1%.On the other hand,the standard afterglow model cannot reproduce the X-ray light curve of GRB 240825A,calling for improved models to characterize all multiwavelength data.展开更多
The nature of progenitors of Type Ia supernovae(SNe Ia)and their explosion mechanism remains unclear.It has been suggested that SNe Ia may have resulted from thermonuclear explosions of hybrid carbon-oxygen-neon white...The nature of progenitors of Type Ia supernovae(SNe Ia)and their explosion mechanism remains unclear.It has been suggested that SNe Ia may have resulted from thermonuclear explosions of hybrid carbon-oxygen-neon white dwarfs(CONe WDs)when they grow in mass to approach the Chandrasekhar mass limit by accreting matter from a binary main-sequence(MS)companion.In this work,we combine the results of detailed binary evolution calculations with population synthesis models to investigate the rates and delay times of SNe Ia in the CONe WD+MS channel at a low metallicity environment of Z=0.0001.For a constant star formation rate of 5M_(⊙)yr^(−1),our calculations predict that the SN Ia rates in the CONe WD+MS channel at low metallicity of Z=0.0001 is about 0.11−3.89×10^(−4) yr^(−1).In addition,delay times in this channel cover a wide range of 0.05−2.5 Gyr.We further compare our results to those given by a previous study for the CONe WD+MS channel with a higher metallicity of Z=0.02 to explore the influence of metallicity on the results.We find that these two metallicity environments give a slight difference in rates and delay times of SNe Ia from the CONe WD+MS channel,although SNe Ia produced at a low metallicity environment of Z=0.0001 have relatively longer delay times.展开更多
Most massive stars reside in binary or multi-object systems.Short gamma-ray bursts(sGRBs),the product of the merger of double compact objects,may originate from massive common-envelope binaries.In contrast,the progeni...Most massive stars reside in binary or multi-object systems.Short gamma-ray bursts(sGRBs),the product of the merger of double compact objects,may originate from massive common-envelope binaries.In contrast,the progenitors of long GRBs(lGRBs)are typically considered isolated massive stars.However,no effective method has yet been established to identify potential companions from current observations.Recent studies have demonstrated that quasi-periodic oscillation signatures can serve as a promising tool to probe the properties of GRB central engines.In this study,by drawing an analogy to periodicity in X-ray binaries,we explore the precession periods of companion-induced disk precession for lGRBs born in the ultra-compact binary scenario.Our results suggest that the periodicity observed in lGRB afterglows,measured in units of 1000 s or more,may indicate that lGRBs originate within binary systems.GRB 050904 could represent a rare case where the burst occurred in a binary system,leaving behind a black hole–black hole binary at redshift z=6.29.展开更多
We use a simple dynamical scheme to simulate the ejecta of type Ⅰa supernova(SN Ia) scenarios with two exploding white dwarfs(WDs) and find that the velocity distribution of the ejecta has difficulties accounting for...We use a simple dynamical scheme to simulate the ejecta of type Ⅰa supernova(SN Ia) scenarios with two exploding white dwarfs(WDs) and find that the velocity distribution of the ejecta has difficulties accounting for bimodal emission line profiles with a large separation between the two emission peaks.The essence of the dynamical code is in including the fact that the ejecta does not leave the system instantaneously.We find that the final separation velocity between the centers of masses of the two WDs' ejecta is ≃80% of the pre-explosion WDs' orbital velocity,i.e.,we find separation velocities of 4200-5400 km s^(-1) for two WDs of masses M_(1)=M_(2)=0.94 M⊙.The lower separation velocities we find challenge scenarios with two exploding WDs to explain bimodal emission line profiles with observed velocity separations of up to ≃7000 km s^(-1).Only the mass in the ejecta of one WD with an explosion velocity lower than the separation velocity contributes to one peak of the bimodal profile;this is the inner ejecta.We find the inner ejecta to be only≲15% of the ejecta mass in energetic explosions.Less energetic explosions yield higher inner mass but lower separation velocities.We encourage searching for alternative explanations of bimodal line profiles.展开更多
Type Ia supernovae(SNe Ia)are among the most extreme phenomena in the Universe and play a crucial role in the studies of stellar evolution,galactic chemical evolution and cosmology.However,the progenitors of SNe Ia ar...Type Ia supernovae(SNe Ia)are among the most extreme phenomena in the Universe and play a crucial role in the studies of stellar evolution,galactic chemical evolution and cosmology.However,the progenitors of SNe Ia are still under debate.It has been suggested that SNe Ia could be produced by helium(He)novae in the singledegenerate channel.Recently,a He nova named[HP99]159 was proposed to be a progenitor candidate for SNe Ia,in which the white dwarf(WD)has a mass of 1.2_(0.4)^(+0.18)M_(⊙),the He star’s mass ranges from 0.8M_(⊙)to 2.0M_(⊙)and the orbital period was suggested to be 2.33 or 1.16 days.In the present work,we evolved a large number of primordial binaries to the formation of WD+He star systems and investigated their future evolution.We provided a representative evolutionary track of[HP99]159 and found that[HP99]159 may originate from a primordial binary with a 6.16M_(⊙)primary and a 4.32M_(⊙)secondary with an initial orbital period of 5110 days.We also found that[HP99]159 might evolve to an SN Ia explosion as suggested by previous studies,or it may also form an accretion-induced collapse event or a wide double WD.Further detailed observations are needed in future studies to provide more information about the precise nature of[HP99]159.展开更多
Using archival Fermi-LAT data with a time span of~12 yr,we study the population of Millisecond Pulsars(MSPs)in Globular Clusters(GlCs)and investigate their dependence on cluster dynamical evolution in the Milky Way.We...Using archival Fermi-LAT data with a time span of~12 yr,we study the population of Millisecond Pulsars(MSPs)in Globular Clusters(GlCs)and investigate their dependence on cluster dynamical evolution in the Milky Way.We show that theγ-ray luminosity(L_(γ))and emissivity(i.e.,ε_(γ)=L_(γ)/M,with M the cluster mass)are good indicators of the population and abundance of MSPs in GlCs,and they are highly dependent on the dynamical evolution history of the host clusters.Specifically speaking,the dynamically older GlCs with more compact structures are more likely to have larger L_(γ)andε_(γ),and these trends can be summarized as strong correlations with cluster stellar encounter rateΓand the specific encounter rate(Λ=Γ/M),with L_(γ)∝Γ^(0.7±0.11)andε_(γ)∝Λ^(0.73±0.13)for dynamically normal GlCs.However,as GlCs evolve into deep core collapse,these trends are found to be reversed,implying that strong encounters may have lead to the disruption of Low-Mass X-ray Binaries and ejection of MSPs from core-collapsed systems.Besides,the GlCs are found to exhibit largerε_(γ)with increasing stellar mass function slope(ε_(γ)∝10^((0.52±0.1)α)),decreasing tidal radius(ε_(γ)∝R_(t)^(-10±0.22))and distances from the Galactic Center(GC,ε_(γ)∝R_(gc)^(-1.13±0.21)).These correlations indicate that,as GlCs losing kinetic energy and spiral in toward the GC,tidal stripping and mass segregation have a preference in leading to the loss of normal stars from GlCs,while MSPs are more likely to concentrate to cluster center and be deposited into the GC.Moreover,we gaugeε_(γ)of GlCs is~10-1000 times larger than the Galactic bulge,the latter is thought to reside thousands of unresolved MSPs and may be responsible for the GC 7-ray excess,which supports that GlCs are generous contributors to the population of MSPs in the GC.展开更多
Strangeon stars,which are proposed to describe the nature of pulsar-like compact stars,have passed various observational tests.The maximum mass of a non-rotating strangeon star could be high,which implies that the rem...Strangeon stars,which are proposed to describe the nature of pulsar-like compact stars,have passed various observational tests.The maximum mass of a non-rotating strangeon star could be high,which implies that the remnants of binary strangeon star mergers could even be long-lived massive strangeon stars.We study rigidly rotating strangeon stars in the slowly rotating approximation,using the Lennard-Jones model for the equation of state.Rotation can significantly increase the maximum mass of strangeon stars with unchanged baryon numbers,enlarging the mass-range of long-lived strangeon stars.During spin-down after merger,the decrease of radius of the remnant will lead to the release of gravitational energy.Taking into account the efficiency of converting the gravitational energy luminosity to the observed X-ray luminosity,we find that the gravitational energy could provide an alternative energy source for the plateau emission of X-ray afterglow.The fitting results of X-ray plateau emission of some short gamma-ray bursts suggest that the magnetic dipole field strength of the remnants can be much smaller than that of expected when the plateau emission is powered only by spin-down luminosity of magnetars.展开更多
In this paper,we analyze the spectral energy distributions of 17 powerful(with a spin-down luminosity greater than10~(35)erg s~(-1))young(with an age less than 15,000 yr)pulsar wind nebulae(PWNe)using a simple timein-...In this paper,we analyze the spectral energy distributions of 17 powerful(with a spin-down luminosity greater than10~(35)erg s~(-1))young(with an age less than 15,000 yr)pulsar wind nebulae(PWNe)using a simple timein-dependent one-zone emission model.Our aim is to investigate correlations between model parameters and the ages of the corresponding PWNe,thereby revealing the evolution of high-energy electron distributions within PWNe.Our findings are as follows:(1)The electron distributions in PWNe can be characterized by a double power-law with a super-exponential cutoff.(2)As PWNe evolve,the high-energy end of the electron distribution spectrum becomes harder with the index decreasing from approximately 3.5 to 2.5,while the low-energy end spectrum index remains constant near 1.5.(3)There is no apparent correlation between the break energy or cutoff energy and the age of PWNe.(4)The average magnetic field within PWNe decreases with age,leading to a positive correlation between the energy loss timescale of electrons at the break energy or the high-energy cutoff and the age of the PWN.(5)The total electron energy within PWNe remains constant near 2×10~(48)erg,while the total magnetic energy decreases with age.展开更多
I further study the manner by which a pair of opposite jets shape the“keyhole”morphological structure of the core-collapse supernova(CCSN)SN 1997A,now the CCSN remnant(CCSNR)1987A.By doing so,I strengthen the claim ...I further study the manner by which a pair of opposite jets shape the“keyhole”morphological structure of the core-collapse supernova(CCSN)SN 1997A,now the CCSN remnant(CCSNR)1987A.By doing so,I strengthen the claim that the jittering-jet explosion mechanism accounts for most,likely all,CCSNe.The“keyhole”structure comprises a northern low-intensity zone closed with a bright rim on its front and an elongated low-intensity nozzle in the south.This rim-nozzle asymmetry is observed in some cooling flow clusters and planetary nebulae that are observed to be shaped by jets.I build a toy model that uses the planar jittering jets pattern,where consecutive pairs of jets tend to jitter in a common plane,implying that the accreted gas onto the newly born neutron star at the late explosion phase flows perpendicular to that plane.This allows for a long-lived jet-launching episode.This long-lasting jet-launching episode launches more mass into the jets that can inflate larger pairs of ears or bubbles,forming the main jets'axis of the CCSNR that is not necessarily related to a possible pre-collapse core rotation.I discuss the relation of the main jets'axis to the neutron star's natal kick velocity.展开更多
We report our identification of three gigaelectronvoltγ-ray sources,4FGL J0502.6+0036,4FGL J1055.9+6507,and 4FGL J1708.2+5519,as Active Galactic Nuclei(AGNs).They are listed in the latest Fermi-Large Area Telescope s...We report our identification of three gigaelectronvoltγ-ray sources,4FGL J0502.6+0036,4FGL J1055.9+6507,and 4FGL J1708.2+5519,as Active Galactic Nuclei(AGNs).They are listed in the latest Fermi-Large Area Telescope source catalog as unidentified ones.We find that the sources all showedγ-ray flux variations in recent years.Using different survey catalogs,we are able to find a radio source within the error circle of each source's position.Further analysis of optical sources in the fields allows us to determine the optical counterparts,which showed similar variation patterns to those seen inγ-rays.The optical counterparts have reported redshifts of 0.6,1.5,and 2.3,respectively,estimated from photometric measurements.In addition,we also obtain an X-ray spectrum of 4FGL J0502.6+0036 and a flux upper limit on the X-ray emission of 4FGL J1055.9+6507 by analyzing the archival data.The broadband spectral energy distributions of the three sources from radio toγ-rays are constructed.Comparing mainly theγ-ray properties of the three sources with those of different sub-classes of AGNs,we tentatively identify them as blazars.Followup optical spectroscopy is highly warranted for obtaining their spectral features and thus verifying the identification.展开更多
Theoretically,a supra-massive neutron star or magnetar may be formed after the merger of binary neutron stars.GRB210323A is a short-duration gamma-ray burst(GRB)with a duration of lasting~1 s.The light curve of the pr...Theoretically,a supra-massive neutron star or magnetar may be formed after the merger of binary neutron stars.GRB210323A is a short-duration gamma-ray burst(GRB)with a duration of lasting~1 s.The light curve of the prompt emission of GRB 210323A shows a signal-peaked structure and a cutoff power-law model can adequately fit the spectra with E_p=1826±747.More interestingly,it has an extremely long-lasting plateau emission in the X-ray afterglow with a duration of~10^(4)s,and then follows a rapid decay with a decay slope~3.2.This temporal feature is challenging by invoking the external shock mode.In this paper,we suggest that the observed long-lasting X-ray plateau emission is caused by the energy injection of dipole radiation from supra-massive magnetar,and the abrupt decay following the longlasting X-ray plateau emission is explained by supra-massive magnetar collapsing into a black hole.It is the short GRB(SGRB)with the longest X-ray internal plateau emission powered by a supra-massive neutron star.If this is the case,one can estimate the physical parameters of a supra-massive magnetar,and compare with other SGRBs.We also discuss the possible gravitational-wave emission,which is powered by a supra-massive magnetar and its detectability,and the possible kilonova emission,which is powered by r-process and magnetar spin-down to compare with the observed data.展开更多
Open clusters are the basic building blocks that serve as a laboratory for the study of young stellar populations in the Milky Way.Variable stars in open clusters provide a unique way to accurately probe the internal ...Open clusters are the basic building blocks that serve as a laboratory for the study of young stellar populations in the Milky Way.Variable stars in open clusters provide a unique way to accurately probe the internal structure,temporal and dynamical evolutionary stages of individual stars and the host cluster.The most powerful tool for such studies is time-domain photometric observations.This paper follows the route of our previous work,concentrating on a photometric search for variable stars in NGC 884.The target cluster is the companion of NGC869,forming the well-known double cluster system that is gravitationally bound.From the observation run in 2016 November,a total of 9247 B-band CCD images and 8218Ⅴ-band CCD images were obtained.We detected a total of 15 stars with variability in visual brightness,including five Be stars,three eclipsing binaries,and seven of unknown types.Two new variable stars were discovered in this work.We also compared the variable star content of NGC 884 with its companion NGC 869.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
In this paper,the emissions from two pulsars,PSRs J1611-0114 and J1617+1123,were investigated using th Five-hundred-meter Aperture Spherical radio Telescope operating at a central frequency of 1250 MHz.Th average puls...In this paper,the emissions from two pulsars,PSRs J1611-0114 and J1617+1123,were investigated using th Five-hundred-meter Aperture Spherical radio Telescope operating at a central frequency of 1250 MHz.Th average pulse profile of PSR J1611-0114 shows two components,the first of which is relatively weak in intensity The two-dimensional pulse stack exhibits an obvious nulling phenomenon,with an estimated nulling fraction o40.1%±5.4%.The durations of the nulls and bursts are consistent with power-law distributions,and no periodi nulling phenomenon is found.The results from PSR J1617+1123 demonstrate that the average pulse profile i composed of four components.The peak intensity of the fourth component varies significantly,causing an unstabl integrated profile.In addition,the modulation characteristics of J1611-0114 and J1617+1123 were studied by analyzing the modulation index,longitude resolved fluctuation spectrum and two-dimensional fluctuation spectrum using the software PSRSALSA.It was found that the two pulsars exhibit intensity modulation.In particular,J1611-0114 displays even-odd modulation,with the modulation period of approximately two pulses.The modulation period of J1617+1123 is relatively broad.There is an obvious subpulse drift phenomenon,and the value of P_(2)i~0.125c/P_(0),corresponding to 12 pulse longitude bins,and the drift rate(P_(2)/P_(3))is about 0.29.展开更多
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 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 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 Key R&D Program(2024YFA1611700)the National Natural Science Foundation of China(grant Nos.12133003,12494571 and 11963001)supported by the Guangxi Talent Program(“Highland of Innovation Talents”)and Program of Bagui Scholars(LHJ)。
文摘SN 2014av is a type Ibn supernova(SN)characterized by the interaction between the SN ejecta and a helium-rich circumstellar medium(CSM).We use the^(56)Ni model,the ejecta-CSM interaction(CSI)model,and the CSI plus^(56)Ni model to fit the multiband light curves(LCs)of SN 2014av.For the CSI and CSI plus^(56)Ni models,we assume that the CSM is a constant density shell(“shell”)or a steady-state stellar wind(“wind”)with density∝r-2.We find that both the^(56)Ni and CSI models fail to fit the multiband LCs of SN 2014av,while the CSI plus^(56)Ni model can account for the LCs.In the last scenario,the LCs around the peaks were mainly powered by the CSI,while the flattening of the LCs was mainly powered by the radioactive decay of^(56)Ni.For the wind case,the derived mass-loss rate of the progenitor is≈20.5-205.5 M_(⊙)yr^(-1),whose lower limit is significantly larger than the upper limit of normal stellar winds,and comparable the upper limit of hyper-winds.Hence,we suggest that the wind case is disfavored.For the shell case,the best-fitting values of the ejecta,^(56)Ni,and the CSM are2.29 M_(⊙),0.09 M_(⊙),and 5.00 M_(⊙),respectively.Provided the velocity of the CSM shell is 100-1000 km s^(-1),we infer that the shell might be expelled≈0.49-5.20 yr before the SN exploded.
基金supported by the National Natural Science Foundation of China (NSFC,grant Nos.12494571,11963001 and 12133003)supported by the Program of Bagui Scholars (LHJ)。
文摘In this paper,we determine the photosphere evolution of PTF11rka which is a type Ic supernova (SN) by fitting its spectral energy distributions at different epochs.We find that the photosphere of PTF11rka expanded at a constant velocity at early epochs,and the photosphere temperature increased slightly after reaching a minimum.These features are reminiscent of those of SN 2017dio.Based on the photosphere module that can describe the photosphere evolution of PTF11rka,we use the ^(56)Ni cascade decay model to fit its multiband light curves (LCs),finding that the model can well fit the photometric data.The derived ejecta mass and ^(56)Ni mass are respectively 8.76■ and 0.29-0.41■;the derived peak luminosity and the rise time of the theoretical bolometric LC of PTF11rka are ~8.24×10^(42)erg s^(-1) and ~35 days,respectively.Moreover,we find that the theoretical multiband LCs and the theoretical bolometric LC of PTF11rka do not show early-time excesses proposed in the literature.This indicates that additional energy sources (e.g.,the interaction between the ejecta and the circumstellar material)suggested to be responsible for the early-time excess can be neglected.
基金supported by the National Key R&D Program of China(grant No.2024YFA1611600)the SVOM project(a mission under the Strategic Priority Program on Space Science of the Chinese Academy of Sciences)+23 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(grant No.XDB0550401)the National Natural Science Foundation of China(NSFC,grant No.12494573)partly supported by Natural Science Foundation of Xinjiang Uygur Autonomous Region(grant No.2024D01D32)Tianshan Talent Training Program(grant No.2023TSYCLJ0053)Tianshan Innovation Team Program(grant No.2024D14015)supported by the Jiangsu Funding Program for Excellent Postdoctoral Talent(grant No.2024ZB110)the Postdoctoral Fellowship Program(grant No.GZC20241916)the General Fund(grant No.2024M763531)of the China Postdoctoral Science Foundationsupported by a Royal Society Dorothy Hodgkin Fellowship(grant Nos.DHF-R1-221175 and DHF-ERE-221005)support by a postdoctoral fellowship from the CNESsupported by the National Key R&D Program of China(grant No.2024YFA1611702)the Strategic Priority Research Program of the Chinese Academy of Sciences(grant No.XDB0550101)the support of the French Agence Nationale de la Recherche(ANR),under grant ANR-23-CE31-0011(project PEGaSUS)financial support from the GRAWITA Large Program Grant(PI P.D’Avanzo)financial support from the Italian Space Agency,contract ASI/INAF No.I/004/11/6support from the INAF project Premiale Supporto Arizona&Italiasupported by the National Natural Science Foundation of China(NSFC,grant No.12133003)supported by the National Natural Science Foundation of China(NSFC,grant No.12373042)the Bagui Scholars Program(No.GXR-6BG2424001)funded by the European Union(ERC,HEAVYMETAL,101071865,Views and opinions expressed are,however,those of the authors only and do not necessarily reflect those of the European Union or the European Research Council Neither the European Union nor the granting authority can be held responsible for them)the Cosmic Dawn Center(DAWN)is funded by the Danish National Research Foundation under grant No.DNRF140supported by the National Natural Science Foundation of China(NSFC,grant Nos.12225305 and 12321003)supported by the National Natural Science Foundation of China(NSFC,grant No.12473049)supported by the General Fund(grant No.2024M763530)of the China Postdoctoral Science Foundation。
文摘Early multiwavelength observations offer crucial insights into the nature of the relativistic jets responsible for gamma-ray bursts and their interaction with the surrounding medium.We present data of GRB 240825A from 17 space-and ground-based telescopes/instruments,covering wavelengths from NIR/optical to X-ray and GeV,and spanning from the prompt emission to the afterglow phase triggered by Swift and Fermi.The early afterglow observations were carried out by SVOM/C-GFT,and spectroscopic observations of the afterglow by GTC,VLT,and TNG determined the redshift of the burst(z=0.659)later.A comprehensive analysis of the prompt emission spectrum observed by Swift-BAT and Fermi-GBM/LAT reveals a rare and significant high-energy cutoff at 76 MeV.Assuming this cutoff is due toγγabsorption allows us to place an upper limit on the initial Lorentz factor,Γ_(0)<245.The optical/NIR and GeV afterglow light curves can be described by the standard external shock model,with early-time emission dominated by a reverse shock(RS)and a subsequent transition to forward shock(FS)emission.Our afterglow modeling yields a consistent estimate of the initial Lorentz factor(Γ_(0)∼234).Furthermore,the RS-to-FS magnetic field ratio(R 302B)indicates that the RS region is significantly more magnetized than the FS region.An isotropic-equivalent kinetic energy of E_(k,iso)=5.25×10^(54) erg is derived,and the correspondingγ-ray radiation efficiency is estimated to beη_(γ)=3.1%.On the other hand,the standard afterglow model cannot reproduce the X-ray light curve of GRB 240825A,calling for improved models to characterize all multiwavelength data.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(grant Nos.XDB1160303,XDB1160000)the National Natural Science Foundation of China(NSFC,Nos.12288102,12333008,12090040/1,11873016,11973080,and 11803030)+3 种基金the National Key R&D Program of China(Nos.2021YFA1600403,2021YFA1600401 and 2021YFA1600400)the Chinese Academy of Sciences(CAS),the Yunnan Ten Thousand Talents Plan–Young&Elite Talents Project,and the CAS“Light of West China”Program,the International Centre of Supernovae,Yunnan Key Laboratory(No.202302AN360001)the Yunnan Fundamental Research Projects(grant Nos.202401BC070007,202201BC070003,and 202001AW070007)the“Yunnan Revitalization Talent Support Program”—Science&Technology Champion Project and Yunling Scholar Project(No.202305AB350003).
文摘The nature of progenitors of Type Ia supernovae(SNe Ia)and their explosion mechanism remains unclear.It has been suggested that SNe Ia may have resulted from thermonuclear explosions of hybrid carbon-oxygen-neon white dwarfs(CONe WDs)when they grow in mass to approach the Chandrasekhar mass limit by accreting matter from a binary main-sequence(MS)companion.In this work,we combine the results of detailed binary evolution calculations with population synthesis models to investigate the rates and delay times of SNe Ia in the CONe WD+MS channel at a low metallicity environment of Z=0.0001.For a constant star formation rate of 5M_(⊙)yr^(−1),our calculations predict that the SN Ia rates in the CONe WD+MS channel at low metallicity of Z=0.0001 is about 0.11−3.89×10^(−4) yr^(−1).In addition,delay times in this channel cover a wide range of 0.05−2.5 Gyr.We further compare our results to those given by a previous study for the CONe WD+MS channel with a higher metallicity of Z=0.02 to explore the influence of metallicity on the results.We find that these two metallicity environments give a slight difference in rates and delay times of SNe Ia from the CONe WD+MS channel,although SNe Ia produced at a low metallicity environment of Z=0.0001 have relatively longer delay times.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(grant No.XDB0550400)the National Key Research and Development Program of China(Nos.2024YFA1611704 and 2021YFA0718500)the National Natural Science Foundation of China(NSFC,Nos.12473049,12041301,12121003,and 12225305).
文摘Most massive stars reside in binary or multi-object systems.Short gamma-ray bursts(sGRBs),the product of the merger of double compact objects,may originate from massive common-envelope binaries.In contrast,the progenitors of long GRBs(lGRBs)are typically considered isolated massive stars.However,no effective method has yet been established to identify potential companions from current observations.Recent studies have demonstrated that quasi-periodic oscillation signatures can serve as a promising tool to probe the properties of GRB central engines.In this study,by drawing an analogy to periodicity in X-ray binaries,we explore the precession periods of companion-induced disk precession for lGRBs born in the ultra-compact binary scenario.Our results suggest that the periodicity observed in lGRB afterglows,measured in units of 1000 s or more,may indicate that lGRBs originate within binary systems.GRB 050904 could represent a rare case where the burst occurred in a binary system,leaving behind a black hole–black hole binary at redshift z=6.29.
文摘We use a simple dynamical scheme to simulate the ejecta of type Ⅰa supernova(SN Ia) scenarios with two exploding white dwarfs(WDs) and find that the velocity distribution of the ejecta has difficulties accounting for bimodal emission line profiles with a large separation between the two emission peaks.The essence of the dynamical code is in including the fact that the ejecta does not leave the system instantaneously.We find that the final separation velocity between the centers of masses of the two WDs' ejecta is ≃80% of the pre-explosion WDs' orbital velocity,i.e.,we find separation velocities of 4200-5400 km s^(-1) for two WDs of masses M_(1)=M_(2)=0.94 M⊙.The lower separation velocities we find challenge scenarios with two exploding WDs to explain bimodal emission line profiles with observed velocity separations of up to ≃7000 km s^(-1).Only the mass in the ejecta of one WD with an explosion velocity lower than the separation velocity contributes to one peak of the bimodal profile;this is the inner ejecta.We find the inner ejecta to be only≲15% of the ejecta mass in energetic explosions.Less energetic explosions yield higher inner mass but lower separation velocities.We encourage searching for alternative explanations of bimodal line profiles.
基金supported by the National Natural Science Foundation of China(NSFC,grant Nos.12288102,12225304,and 12090040/12090043)the National Key R&D Program of China(No.2021YFA1600404)+3 种基金the Western Light Project of CAS(No.XBZG-ZDSYS-202117)the Yunnan Revitalization Talent Support Program(Yunling Scholar Project)the Yunnan Fundamental Research Project(No.202201BC070003)the International Centre of Supernovae,Yunnan Key Laboratory(No.202302AN360001).
文摘Type Ia supernovae(SNe Ia)are among the most extreme phenomena in the Universe and play a crucial role in the studies of stellar evolution,galactic chemical evolution and cosmology.However,the progenitors of SNe Ia are still under debate.It has been suggested that SNe Ia could be produced by helium(He)novae in the singledegenerate channel.Recently,a He nova named[HP99]159 was proposed to be a progenitor candidate for SNe Ia,in which the white dwarf(WD)has a mass of 1.2_(0.4)^(+0.18)M_(⊙),the He star’s mass ranges from 0.8M_(⊙)to 2.0M_(⊙)and the orbital period was suggested to be 2.33 or 1.16 days.In the present work,we evolved a large number of primordial binaries to the formation of WD+He star systems and investigated their future evolution.We provided a representative evolutionary track of[HP99]159 and found that[HP99]159 may originate from a primordial binary with a 6.16M_(⊙)primary and a 4.32M_(⊙)secondary with an initial orbital period of 5110 days.We also found that[HP99]159 might evolve to an SN Ia explosion as suggested by previous studies,or it may also form an accretion-induced collapse event or a wide double WD.Further detailed observations are needed in future studies to provide more information about the precise nature of[HP99]159.
基金supported by the Youth Program of the National Natural Science Foundation of China No.12003017。
文摘Using archival Fermi-LAT data with a time span of~12 yr,we study the population of Millisecond Pulsars(MSPs)in Globular Clusters(GlCs)and investigate their dependence on cluster dynamical evolution in the Milky Way.We show that theγ-ray luminosity(L_(γ))and emissivity(i.e.,ε_(γ)=L_(γ)/M,with M the cluster mass)are good indicators of the population and abundance of MSPs in GlCs,and they are highly dependent on the dynamical evolution history of the host clusters.Specifically speaking,the dynamically older GlCs with more compact structures are more likely to have larger L_(γ)andε_(γ),and these trends can be summarized as strong correlations with cluster stellar encounter rateΓand the specific encounter rate(Λ=Γ/M),with L_(γ)∝Γ^(0.7±0.11)andε_(γ)∝Λ^(0.73±0.13)for dynamically normal GlCs.However,as GlCs evolve into deep core collapse,these trends are found to be reversed,implying that strong encounters may have lead to the disruption of Low-Mass X-ray Binaries and ejection of MSPs from core-collapsed systems.Besides,the GlCs are found to exhibit largerε_(γ)with increasing stellar mass function slope(ε_(γ)∝10^((0.52±0.1)α)),decreasing tidal radius(ε_(γ)∝R_(t)^(-10±0.22))and distances from the Galactic Center(GC,ε_(γ)∝R_(gc)^(-1.13±0.21)).These correlations indicate that,as GlCs losing kinetic energy and spiral in toward the GC,tidal stripping and mass segregation have a preference in leading to the loss of normal stars from GlCs,while MSPs are more likely to concentrate to cluster center and be deposited into the GC.Moreover,we gaugeε_(γ)of GlCs is~10-1000 times larger than the Galactic bulge,the latter is thought to reside thousands of unresolved MSPs and may be responsible for the GC 7-ray excess,which supports that GlCs are generous contributors to the population of MSPs in the GC.
基金supported by the National SKA Program of China(Nos.2020SKA0120300,2020SKA0120100)the Outstanding Young and Middle-aged Science and Technology Innovation Teams from Hubei colleges and universities(No.T2021026)the Young Top-notch Talent Cultivation Program of Hubei Province,and the Key Laboratory Opening Fund(MOE)of China(grant No.QLPL2021P01)。
文摘Strangeon stars,which are proposed to describe the nature of pulsar-like compact stars,have passed various observational tests.The maximum mass of a non-rotating strangeon star could be high,which implies that the remnants of binary strangeon star mergers could even be long-lived massive strangeon stars.We study rigidly rotating strangeon stars in the slowly rotating approximation,using the Lennard-Jones model for the equation of state.Rotation can significantly increase the maximum mass of strangeon stars with unchanged baryon numbers,enlarging the mass-range of long-lived strangeon stars.During spin-down after merger,the decrease of radius of the remnant will lead to the release of gravitational energy.Taking into account the efficiency of converting the gravitational energy luminosity to the observed X-ray luminosity,we find that the gravitational energy could provide an alternative energy source for the plateau emission of X-ray afterglow.The fitting results of X-ray plateau emission of some short gamma-ray bursts suggest that the magnetic dipole field strength of the remnants can be much smaller than that of expected when the plateau emission is powered only by spin-down luminosity of magnetars.
基金supported by the National Natural Science Foundation of China(Nos.12220101003,12273114,U1931204,12103040,12147208 and U2031111)the Project for Young Scientists in Basic Research of Chinese Academy of Sciences(No.YSBR-061)the Program for Innovative Talents and Entrepreneur in Jiangsu。
文摘In this paper,we analyze the spectral energy distributions of 17 powerful(with a spin-down luminosity greater than10~(35)erg s~(-1))young(with an age less than 15,000 yr)pulsar wind nebulae(PWNe)using a simple timein-dependent one-zone emission model.Our aim is to investigate correlations between model parameters and the ages of the corresponding PWNe,thereby revealing the evolution of high-energy electron distributions within PWNe.Our findings are as follows:(1)The electron distributions in PWNe can be characterized by a double power-law with a super-exponential cutoff.(2)As PWNe evolve,the high-energy end of the electron distribution spectrum becomes harder with the index decreasing from approximately 3.5 to 2.5,while the low-energy end spectrum index remains constant near 1.5.(3)There is no apparent correlation between the break energy or cutoff energy and the age of PWNe.(4)The average magnetic field within PWNe decreases with age,leading to a positive correlation between the energy loss timescale of electrons at the break energy or the high-energy cutoff and the age of the PWN.(5)The total electron energy within PWNe remains constant near 2×10~(48)erg,while the total magnetic energy decreases with age.
文摘I further study the manner by which a pair of opposite jets shape the“keyhole”morphological structure of the core-collapse supernova(CCSN)SN 1997A,now the CCSN remnant(CCSNR)1987A.By doing so,I strengthen the claim that the jittering-jet explosion mechanism accounts for most,likely all,CCSNe.The“keyhole”structure comprises a northern low-intensity zone closed with a bright rim on its front and an elongated low-intensity nozzle in the south.This rim-nozzle asymmetry is observed in some cooling flow clusters and planetary nebulae that are observed to be shaped by jets.I build a toy model that uses the planar jittering jets pattern,where consecutive pairs of jets tend to jitter in a common plane,implying that the accreted gas onto the newly born neutron star at the late explosion phase flows perpendicular to that plane.This allows for a long-lived jet-launching episode.This long-lasting jet-launching episode launches more mass into the jets that can inflate larger pairs of ears or bubbles,forming the main jets'axis of the CCSNR that is not necessarily related to a possible pre-collapse core rotation.I discuss the relation of the main jets'axis to the neutron star's natal kick velocity.
基金supported by the Basic Research Program of Yunnan Province(No.202201AS070005)the National Natural Science Foundation of China(NSFC,grant No.12273033)+1 种基金the Original Innovation Program of the Chinese Academy of Sciences(E085021002)support of the science research program for graduate students of Yunnan University(KC-23234629)。
文摘We report our identification of three gigaelectronvoltγ-ray sources,4FGL J0502.6+0036,4FGL J1055.9+6507,and 4FGL J1708.2+5519,as Active Galactic Nuclei(AGNs).They are listed in the latest Fermi-Large Area Telescope source catalog as unidentified ones.We find that the sources all showedγ-ray flux variations in recent years.Using different survey catalogs,we are able to find a radio source within the error circle of each source's position.Further analysis of optical sources in the fields allows us to determine the optical counterparts,which showed similar variation patterns to those seen inγ-rays.The optical counterparts have reported redshifts of 0.6,1.5,and 2.3,respectively,estimated from photometric measurements.In addition,we also obtain an X-ray spectrum of 4FGL J0502.6+0036 and a flux upper limit on the X-ray emission of 4FGL J1055.9+6507 by analyzing the archival data.The broadband spectral energy distributions of the three sources from radio toγ-rays are constructed.Comparing mainly theγ-ray properties of the three sources with those of different sub-classes of AGNs,we tentatively identify them as blazars.Followup optical spectroscopy is highly warranted for obtaining their spectral features and thus verifying the identification.
基金supported by the Guangxi Science Foundation(grant No.2023GXNSFDA026007)the Program of Bagui Scholars Program(LHJ)。
文摘Theoretically,a supra-massive neutron star or magnetar may be formed after the merger of binary neutron stars.GRB210323A is a short-duration gamma-ray burst(GRB)with a duration of lasting~1 s.The light curve of the prompt emission of GRB 210323A shows a signal-peaked structure and a cutoff power-law model can adequately fit the spectra with E_p=1826±747.More interestingly,it has an extremely long-lasting plateau emission in the X-ray afterglow with a duration of~10^(4)s,and then follows a rapid decay with a decay slope~3.2.This temporal feature is challenging by invoking the external shock mode.In this paper,we suggest that the observed long-lasting X-ray plateau emission is caused by the energy injection of dipole radiation from supra-massive magnetar,and the abrupt decay following the longlasting X-ray plateau emission is explained by supra-massive magnetar collapsing into a black hole.It is the short GRB(SGRB)with the longest X-ray internal plateau emission powered by a supra-massive neutron star.If this is the case,one can estimate the physical parameters of a supra-massive magnetar,and compare with other SGRBs.We also discuss the possible gravitational-wave emission,which is powered by a supra-massive magnetar and its detectability,and the possible kilonova emission,which is powered by r-process and magnetar spin-down to compare with the observed data.
基金the National Natural Science Foundation of China(NSFC)through grants 12003022,12373035,12233009 and 12173047support from the Youth Innovation Promotion Association of the CAS(grant No.2022055)。
文摘Open clusters are the basic building blocks that serve as a laboratory for the study of young stellar populations in the Milky Way.Variable stars in open clusters provide a unique way to accurately probe the internal structure,temporal and dynamical evolutionary stages of individual stars and the host cluster.The most powerful tool for such studies is time-domain photometric observations.This paper follows the route of our previous work,concentrating on a photometric search for variable stars in NGC 884.The target cluster is the companion of NGC869,forming the well-known double cluster system that is gravitationally bound.From the observation run in 2016 November,a total of 9247 B-band CCD images and 8218Ⅴ-band CCD images were obtained.We detected a total of 15 stars with variability in visual brightness,including five Be stars,three eclipsing binaries,and seven of unknown types.Two new variable stars were discovered in this work.We also compared the variable star content of NGC 884 with its companion NGC 869.
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.
基金supported by National Key Research and Development Program of China(2022YFC2205203)the Major Science and Technology Program of Xinjiang Uygur Autonomous Region(No.2022A03013-1)+9 种基金the National Natural Science Foundation of China(NSFC,grant Nos.U1838109 and 12041304)supported by the Major Science and Technology Program of Xinjiang Uygur Autonomous Region(No.2022A03013-1)National Natural Science Foundation of China(NSFC,Grant No.12303053)the 2021 project Xinjiang Uygur autonomous region of China for Tianshan elites,the Youth Innovation Promotion Association of CAS under No.2023069the Tianshan Talent Training Program(No.2023TSYCCX0100)supported by the National SKA Program of China(grant No.2020SKA0120200)the National Natural Science Foundation of China(NSFC,grant Nos.12041303,12273100 and12288102)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)。
文摘In this paper,the emissions from two pulsars,PSRs J1611-0114 and J1617+1123,were investigated using th Five-hundred-meter Aperture Spherical radio Telescope operating at a central frequency of 1250 MHz.Th average pulse profile of PSR J1611-0114 shows two components,the first of which is relatively weak in intensity The two-dimensional pulse stack exhibits an obvious nulling phenomenon,with an estimated nulling fraction o40.1%±5.4%.The durations of the nulls and bursts are consistent with power-law distributions,and no periodi nulling phenomenon is found.The results from PSR J1617+1123 demonstrate that the average pulse profile i composed of four components.The peak intensity of the fourth component varies significantly,causing an unstabl integrated profile.In addition,the modulation characteristics of J1611-0114 and J1617+1123 were studied by analyzing the modulation index,longitude resolved fluctuation spectrum and two-dimensional fluctuation spectrum using the software PSRSALSA.It was found that the two pulsars exhibit intensity modulation.In particular,J1611-0114 displays even-odd modulation,with the modulation period of approximately two pulses.The modulation period of J1617+1123 is relatively broad.There is an obvious subpulse drift phenomenon,and the value of P_(2)i~0.125c/P_(0),corresponding to 12 pulse longitude bins,and the drift rate(P_(2)/P_(3))is about 0.29.
