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
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
The triggering mechanism for radio lobes from late-type galaxies is not fully understood.More samples are desired for a thorough investigation and statistics.By utilizing the optical data from the newly released Dark ...The triggering mechanism for radio lobes from late-type galaxies is not fully understood.More samples are desired for a thorough investigation and statistics.By utilizing the optical data from the newly released Dark Energy Spectroscopic Instrument imaging surveys and the radio sources from the NRAO VLA Sky Survey and the Faint Images of the Radio Sky at Twenty-centimeter,we identify four Late-type Galaxies with double Radio Lobes(La GRLs):J0217-3645,J0947+6220,J1412+3723 and J1736+5108.Including previously known La GRLs,we confirm the correlation between radio power P_(1.4GHz)and stellar mass M_(*)of host galaxies.Most(25/35)La GRLs belong to the blue cloud galaxies,while the newly identified cases in this work are located within the region of the red sequence.We find a clear correlation between the differential radio power,i.e.,the offset from the P_(1.4GHz)-M_(*)relation,and the galaxy color,indicating that bluer galaxies at a fixed M_(*)tend to host more powerful radio lobes.Furthermore,the majority(31/36)of La GRLs are either located in a galaxy group or displaying a disturbed morphology.We suggest that all of the galaxy mass,color and surrounding environment could play important roles in triggering radio lobes in late-type galaxies.展开更多
Discovery of pulsars is one of the main goals for large radio telescopes.The Five-hundredmeter Aperture Spherical radio Telescope(FAST),that incorporates an L-band 19-beam receiver with a system temperature of about 2...Discovery of pulsars is one of the main goals for large radio telescopes.The Five-hundredmeter Aperture Spherical radio Telescope(FAST),that incorporates an L-band 19-beam receiver with a system temperature of about 20 K,is the most sensitive radio telescope utilized for discovering pulsars.We designed the snapshot observation mode for a FAST key science project,the Galactic Plane Pulsar Snapshot(GPPS)survey,in which every four nearby pointings can observe a cover of a sky patch of 0.1575 square degrees through beam-switching of the L-band 19-beam receiver.The integration time for each pointing is 300 seconds so that the GPPS observations for a cover can be made in 21 minutes.The goal of the GPPS survey is to discover pulsars within the Galactic latitude of±10∘from the Galactic plane,and the highest priority is given to the inner Galaxy within±5∘.Up to now,the GPPS survey has discovered 201 pulsars,including currently the faintest pulsars which cannot be detected by other telescopes,pulsars with extremely high dispersion measures(DMs)which challenge the currently widely used models for the Galactic electron density distribution,pulsars coincident with supernova remnants,40 millisecond pulsars,16 binary pulsars,some nulling and mode-changing pulsars and rotating radio transients(RRATs).The follow-up observations for confirmation of new pulsars have polarization-signals recorded for polarization profiles of the pulsars.Re-detection of previously known pulsars in the survey data also leads to significant improvements in parameters for 64 pulsars.The GPPS survey discoveries are published and will be updated at http://zmtt.bao.ac.cn/GPPS/.展开更多
We report the properties of more than 800 bursts detected from the repeating fast radio burst(FRB)source FRB 20201124A with the Five-hundred-meter Aperture Spherical radio Telescope during an extremely active episode ...We report the properties of more than 800 bursts detected from the repeating fast radio burst(FRB)source FRB 20201124A with the Five-hundred-meter Aperture Spherical radio Telescope during an extremely active episode on UTC 2021 September 25th-28th in a series of four papers.In this fourth paper of the series,we present a systematic search of the spin period and linear acceleration of the source object from both 996 individual pulse peaks and the dedispersed time series.No credible spin period was found from this data set.We rule out the presence of significant periodicity in the range between 1 ms and 100 s with a pulse duty cycle<0.49±0.08(when the profile is defined by a von-Mises function,not a boxcar function)and linear acceleration up to 300 m s^(-2)in each of the four one-hour observing sessions,and up to 0.6 m s^(-2)in all 4 days.These searches contest theoretical scenarios involving a 1 ms–100 s isolated magnetar/pulsar with surface magnetic field<10^(15)G and a small duty cycle(such as in a polar-cap emission mode)or a pulsar with a companion star or black hole up to 100 M_(⊙)and P_(b)>10 hr.We also perform a periodicity search of the fine structures and identify 53 unrelated millisecond-timescale“periods”in multicomponents with the highest significance of 3.9σ.The“periods”recovered from the fine structures are neither consistent nor harmonically related.Thus they are not likely to come from a spin period.We caution against claiming spin periodicity with significance below~4σwith multi-components from one-off FRBs.We discuss the implications of our results and the possible connections between FRB multi-components and pulsar microstructures.展开更多
We report the properties of more than 600 bursts(including cluster-bursts)detected from the repeating fast radio burst(FRB)source FRB 20201124A with the Five-hundred-meter Aperture Spherical radio Telescope during an ...We report the properties of more than 600 bursts(including cluster-bursts)detected from the repeating fast radio burst(FRB)source FRB 20201124A with the Five-hundred-meter Aperture Spherical radio Telescope during an extremely active episode on UTC 2021 September 25–28,in a series of four papers.The observations were carried out in the band of 1.0–1.5 GHz by using the center beam of the L-band 19-beam receiver.We monitored the source in sixteen1 hr sessions and one 3 hr session spanning 23 days.All the bursts were detected during the first four days.In this first paper of the series,we perform a detailed morphological study of 624 bursts using the two-dimensional frequencytime“waterfall”plots,with a burst(or cluster-burst)defined as an emission episode during which the adjacent emission peaks have a separation shorter than 400 ms.The duration of a burst is therefore always longer than 1 ms,with the longest up to more than 120 ms.The emission spectra of the sub-bursts are typically narrow within the observing band with a characteristic width of~277 MHz.The center frequency distribution has a dominant peak at about 1091.9 MHz and a secondary weak peak around 1327.9 MHz.Most bursts show a frequencydownwarddrifting pattern.Based on the drifting patterns,we classify the bursts into five main categories:downward drifting(263)bursts,upward drifting(3)bursts,complex(203),no drifting(35)bursts,and no evidence for drifting(121)bursts.Subtypes are introduced based on the emission frequency range in the band(low,middle,high and wide)as well as the number of components in one burst(1,2,or multiple).We measured a varying scintillation bandwidth from about 0.5 MHz at 1.0 GHz to 1.4 MHz at 1.5 GHz with a spectral index of 3.0.展开更多
We have carried out the Galactic Plane Pulsar Snapshot(GPPS)survey by using the Five-hundred-meter Aperture Spherical radio Telescope(FAST),the most sensitive systematic pulsar survey in the Galactic plane.In addition...We have carried out the Galactic Plane Pulsar Snapshot(GPPS)survey by using the Five-hundred-meter Aperture Spherical radio Telescope(FAST),the most sensitive systematic pulsar survey in the Galactic plane.In addition to more than 500 pulsars already discovered through normal periodical search,we report here the discovery of 76 new transient radio sources with sporadic strong pulses,detected by using the newly developed module for a sensitive single-pulse search.Their small DM values suggest that they all are Galactic rotating radio transients(RRATs).They show different properties in the follow-up observations.More radio pulses have been detected from 26 transient radio sources but no periods can be found due to a limited small number of pulses from all FAST observations.The followup observations show that 16 transient sources are newly identified as being the prototypes of RRATs with a period already determined from more detected sporadic pulses,and 10 sources are extremely nulling pulsars,and 24 sources are weak pulsars with sparse strong pulses.On the other hand,48 previously known RRATs have been detected by the FAST,either during verification observations for the GPPS survey or through targeted observations of applied normal FAST projects.Except for one RRAT with four pulses detected in a session of 5-minute observation and four RRATs with only one pulse detected in a session,sensitive FAST observations reveal that 43 RRATs are just generally weak pulsars with sporadic strong pulses or simply very nulling pulsars,so that the previously known RRATs always have an extreme emission state together with a normal hardly detectable weak emission state.This is echoed by the two normal pulsars J1938+2213 and J1946+1449 with occasional brightening pulses.Though strong pulses of RRATs are very outstanding in the energy distribution,their polarization angle variations follow the polarization angle curve of the averaged normal pulse profile,suggesting that the predominant sparse pulses of RRATs are emitted in the same region with the same geometry as normal weak pulsars.展开更多
Pulsar polarization profiles form a very basic database for understanding the emission processes in a pulsar magnetosphere.After careful polarization calibration of the 19-beam L-band receiver and verification of beam...Pulsar polarization profiles form a very basic database for understanding the emission processes in a pulsar magnetosphere.After careful polarization calibration of the 19-beam L-band receiver and verification of beamoffset observation results,we obtain polarization profiles of 682 pulsars from observations by the Five-hundredmeter Aperture Spherical radio Telescope(FAST)duringthe Galactic Plane Pulsar Snapshot survey and other normal FAST projects.Among them,polarization profiles of about 460 pulsars are observed for the first time.The profiles exhibit diverse features.Some pulsars have a polarization position angle curve with a good S-shaped swing,some with orthogonal modes;some have components with highly linearly polarized components or strong circularly polarized components;some have a very wide profile,coming from an aligned rotator,and some have an interpulse from a perpendicular rotator;some wide profiles are caused by interstellar scattering.We derive geometric parameters for 190 pulsars from the S-shaped position angle curves or with orthogonal modes.We find that the linear and circular polarization or the widths of pulse profiles have various frequency dependencies.Pulsars with a large fraction of linear polarization are more likely to have a large Edot.展开更多
Double radio lobes are generally believed to be produced by active nuclei of elliptical galaxies.However,several double-lobed radio sources have been solidly found to be associated with spiral galaxies.By cross-matchi...Double radio lobes are generally believed to be produced by active nuclei of elliptical galaxies.However,several double-lobed radio sources have been solidly found to be associated with spiral galaxies.By cross-matching~9×105 spiral galaxies selected from the Sloan Digital Sky Survey DR8 data with the full 1.4 GHz radio source catalogs of NRAO VLA Sky Survey and Faint Images of the Radio Sky at Twenty-centimeters,we identify three new spiral galaxies:J0326-0623,J1110+0321 and J1134+3046 that produce double radio lobes,and five doublelobed spirals previously known.By combining the newly discovered and all the other known cases in literature,we confirm the relation that more massive spiral galaxies could produce more powerful radio lobes.We find that most of these spiral galaxies are located in a galaxy group or a poor cluster,in which the environment is denser than in the field,and about half of them are the central brightest galaxies in their parent system.We therefore suggest that the environment is one of the key factors for a spiral to produce double radio lobes.展开更多
Fast radio bursts show large dispersion measures, much larger than the Galactic dispersion measure foreground. Therefore, they evidently have an extragalac- tic origin. We investigate possible contributions to the dis...Fast radio bursts show large dispersion measures, much larger than the Galactic dispersion measure foreground. Therefore, they evidently have an extragalac- tic origin. We investigate possible contributions to the dispersion measure from host galaxies. We simulate the spatial distribution of fast radio bursts and calculate the dis- persion measures along the sightlines from fast radio bursts to the edge of host galaxies by using the scaled NE2001 model for thermal electron density distributions. We find that contributions to the dispersion measure of fast radio bursts from the host galaxy follow a skew Gaussian distribution. The peak and the width at half maximum of the dispersion measure distribution increase with the inclination angle of a spiral galaxy, to large values when the inclination angle is over 70~. The largest dispersion measure produced by an edge-on spiral galaxy can reach a few thousand pc cm-3, while the dispersion measures from dwarf galaxies and elliptical galaxies have a maximum of only a few tens of pc cm-3. Notice, however, that additional dispersion measures of tens to hundreds of pc cm-3 can be produced by high density clumps in host galaxies. Simulations that include dispersion measure contributions from the Large Magellanic Cloud and the Andromeda Galaxy are shown as examples to demonstrate how to ex- tract the dispersion measure from the intergalactic medium.展开更多
Radio astronomy observations are frequently impacted by radio frequency interference(RFI).We propose a novel method,named 2σCRF,for cleaning RFI in the folded data of pulsar observations,utilizing a Bayesian-based mo...Radio astronomy observations are frequently impacted by radio frequency interference(RFI).We propose a novel method,named 2σCRF,for cleaning RFI in the folded data of pulsar observations,utilizing a Bayesian-based model called conditional random fields(CRFs).This algorithm minimizes the“energy”of every pixel given an initial label.The standard deviations(i.e.,rms values)of the folded pulsar data are utilized as pixels for all subintegrations and channels.Non-RFI data without obvious interference is treated as“background noise,”while RFI-affected data have different classes due to their exceptional rms values.This initial labeling can be automated and is adaptive to the actual data.The CRF algorithm optimizes the label category for each pixel of the image with the prior initial labels.We demonstrate the efficacy of the proposed method on pulsar folded data obtained from Five-hundred-meter Aperture Spherical radio Telescope observations.It can effectively recognize and tag various categories of RFIs,including broadband or narrowband,constant or instantaneous,and even weak RFIs that are unrecognizable in some pixels but picked out based on their neighborhoods.The results are comparable to those obtained via manual labeling but without the need for human intervention,saving time and effort.展开更多
Previous studies have identified two emission modes in PSR B1859+07: a normal mode that has three prominent components in the average profile, with the trailing one being the brightest, and an anomalous mode(i.e., the...Previous studies have identified two emission modes in PSR B1859+07: a normal mode that has three prominent components in the average profile, with the trailing one being the brightest, and an anomalous mode(i.e., the A mode) where emissions seem to be shifted to an earlier phase. Within the normal mode, further analysis has revealed the presence of two submodes, i.e., the cW mode and c B mode, where the central component can appear either weak or bright. As for the anomalous mode, a new bright component emerges in the advanced phase while the bright trailing component in the normal mode disappears. New observations of PSR B1859+07 using the Fivehundred-meter Aperture Spherical Radio Telescope(FAST) have revealed the existence of a previously unknown emission mode, dubbed the Af mode. In this mode, all emission components seen in the normal and anomalous modes are detected. Notably, the mean polarization profiles of both the A and Af modes exhibit a jump in the orthogonal polarization angle modesin the bright leading component. The polarization angles for the central component in the original normal mode follow two distinct orthogonal polarization modes in the A and Af modes respectively. The polarization angles for the trailing component show almost the same but a small systematic shift in the A and Af modes, roughly following the values for the c W and cB modes. Those polarization features of this newly detected emission mode imply that the anomalous mode A of PSR B1859+07 is not a result of “phase shift”or “swooshes” of normal components, but simply a result of the varying intensities of different profile components.Additionally, subpulse drifting has been detected in the leading component of the Af mode.展开更多
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: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partially supported by the National SKA Program of China(grant No.2022SKA0120103)the National Natural Science Foundation of China(Nos.11988101 and 11833009,12073036)+2 种基金support from the science research grants from the China Manned Space Project(CMS-CSST-2021-A01,CMS-CSST-2021-B01)the financial support from the National Key R&D Program of China(No.2021YFA1600401 and 2021YFA1600400)the International Partnership Program of Chinese Academy of Sciences,grant No.114A11KYSB20170044。
文摘The triggering mechanism for radio lobes from late-type galaxies is not fully understood.More samples are desired for a thorough investigation and statistics.By utilizing the optical data from the newly released Dark Energy Spectroscopic Instrument imaging surveys and the radio sources from the NRAO VLA Sky Survey and the Faint Images of the Radio Sky at Twenty-centimeter,we identify four Late-type Galaxies with double Radio Lobes(La GRLs):J0217-3645,J0947+6220,J1412+3723 and J1736+5108.Including previously known La GRLs,we confirm the correlation between radio power P_(1.4GHz)and stellar mass M_(*)of host galaxies.Most(25/35)La GRLs belong to the blue cloud galaxies,while the newly identified cases in this work are located within the region of the red sequence.We find a clear correlation between the differential radio power,i.e.,the offset from the P_(1.4GHz)-M_(*)relation,and the galaxy color,indicating that bluer galaxies at a fixed M_(*)tend to host more powerful radio lobes.Furthermore,the majority(31/36)of La GRLs are either located in a galaxy group or displaying a disturbed morphology.We suggest that all of the galaxy mass,color and surrounding environment could play important roles in triggering radio lobes in late-type galaxies.
基金This project,as one of five key projects,is being carried out by using FAST,a Chinese national mega-science facility built and operated by the National Astronomical Observatories,Chinese Academy of Sciences.J.L.Han is supported by the National Natural Science Foundation of China(NSFC,Nos.11988101 and 11833009)the Key Research Program of the Chinese Academy of Sciences(Grant No.QYZDJ-SSW-SLH021)+4 种基金C.Wang is partially supported by NSFC No.U1731120X.Y.Gao is partially supported by NSFC No.U1831103P.F.Wang is partially supported by the NSFC No.11873058 and the National SKA program of China No.2020SKA0120200.Jun Xu is partially supported by NSFC No.U2031115H.G.Wang is partially supported by the National SKA program of China(No.2020SKA0120100)R.Yuen is partly supported by Xiaofeng Yang's Xinjiang Tianchi Bairen project and CAS Pioneer Hundred Talents Program.L.G.Hou thanks the support from the Youth Innovation Promotion Association CAS.
文摘Discovery of pulsars is one of the main goals for large radio telescopes.The Five-hundredmeter Aperture Spherical radio Telescope(FAST),that incorporates an L-band 19-beam receiver with a system temperature of about 20 K,is the most sensitive radio telescope utilized for discovering pulsars.We designed the snapshot observation mode for a FAST key science project,the Galactic Plane Pulsar Snapshot(GPPS)survey,in which every four nearby pointings can observe a cover of a sky patch of 0.1575 square degrees through beam-switching of the L-band 19-beam receiver.The integration time for each pointing is 300 seconds so that the GPPS observations for a cover can be made in 21 minutes.The goal of the GPPS survey is to discover pulsars within the Galactic latitude of±10∘from the Galactic plane,and the highest priority is given to the inner Galaxy within±5∘.Up to now,the GPPS survey has discovered 201 pulsars,including currently the faintest pulsars which cannot be detected by other telescopes,pulsars with extremely high dispersion measures(DMs)which challenge the currently widely used models for the Galactic electron density distribution,pulsars coincident with supernova remnants,40 millisecond pulsars,16 binary pulsars,some nulling and mode-changing pulsars and rotating radio transients(RRATs).The follow-up observations for confirmation of new pulsars have polarization-signals recorded for polarization profiles of the pulsars.Re-detection of previously known pulsars in the survey data also leads to significant improvements in parameters for 64 pulsars.The GPPS survey discoveries are published and will be updated at http://zmtt.bao.ac.cn/GPPS/.
基金supported by the National SKA Program of China(Nos.2020SKA0120200 and 2020SKA0120100)the National Natural Science Foundation of China(Grant Nos.12041303,11873067 and 12041304)+4 种基金the National Key R&D Program of China(Nos.2017YFA0402600,2021YFA0718500 and 2017YFA0402602)the CAS-MPG LEGACY project,the Max-Planck Partner Group,the Key Research Project of Zhejiang Lab(No.2021PE0AC0)supported by the National Natural Science Foundation of China(NSFC,Nos.11988101 and 11833009)the Key Research Program of the Chinese Academy of Sciences(Grant No.QYZDJ-SSWSLH021)supported by the Cultivation Project for the FAST scientific Payoff and Research Achievement of CAMS-CAS。
文摘We report the properties of more than 800 bursts detected from the repeating fast radio burst(FRB)source FRB 20201124A with the Five-hundred-meter Aperture Spherical radio Telescope during an extremely active episode on UTC 2021 September 25th-28th in a series of four papers.In this fourth paper of the series,we present a systematic search of the spin period and linear acceleration of the source object from both 996 individual pulse peaks and the dedispersed time series.No credible spin period was found from this data set.We rule out the presence of significant periodicity in the range between 1 ms and 100 s with a pulse duty cycle<0.49±0.08(when the profile is defined by a von-Mises function,not a boxcar function)and linear acceleration up to 300 m s^(-2)in each of the four one-hour observing sessions,and up to 0.6 m s^(-2)in all 4 days.These searches contest theoretical scenarios involving a 1 ms–100 s isolated magnetar/pulsar with surface magnetic field<10^(15)G and a small duty cycle(such as in a polar-cap emission mode)or a pulsar with a companion star or black hole up to 100 M_(⊙)and P_(b)>10 hr.We also perform a periodicity search of the fine structures and identify 53 unrelated millisecond-timescale“periods”in multicomponents with the highest significance of 3.9σ.The“periods”recovered from the fine structures are neither consistent nor harmonically related.Thus they are not likely to come from a spin period.We caution against claiming spin periodicity with significance below~4σwith multi-components from one-off FRBs.We discuss the implications of our results and the possible connections between FRB multi-components and pulsar microstructures.
基金supported by the National Natural Science Foundation of China(NSFC,Nos.11988101 and 11833009)the Key Research Program of the Chinese Academy of Sciences(Grant No.QYZDJ-SSWSLH021)+6 种基金supported by the Cultivation Project for the FAST scientific Payoff and Research Achievement of CAMS-CASsupported by the Key Research Project of Zhejiang Lab no.2021PE0AC0supported by the National SKA Program of China(2020SKA0120100)the National Key R&D Program of China(2017YFA0402602)the National Natural Science Foundation of China(No.12041303)the CAS-MPG LEGACY projectfunding from the MaxPlanck Partner Group。
文摘We report the properties of more than 600 bursts(including cluster-bursts)detected from the repeating fast radio burst(FRB)source FRB 20201124A with the Five-hundred-meter Aperture Spherical radio Telescope during an extremely active episode on UTC 2021 September 25–28,in a series of four papers.The observations were carried out in the band of 1.0–1.5 GHz by using the center beam of the L-band 19-beam receiver.We monitored the source in sixteen1 hr sessions and one 3 hr session spanning 23 days.All the bursts were detected during the first four days.In this first paper of the series,we perform a detailed morphological study of 624 bursts using the two-dimensional frequencytime“waterfall”plots,with a burst(or cluster-burst)defined as an emission episode during which the adjacent emission peaks have a separation shorter than 400 ms.The duration of a burst is therefore always longer than 1 ms,with the longest up to more than 120 ms.The emission spectra of the sub-bursts are typically narrow within the observing band with a characteristic width of~277 MHz.The center frequency distribution has a dominant peak at about 1091.9 MHz and a secondary weak peak around 1327.9 MHz.Most bursts show a frequencydownwarddrifting pattern.Based on the drifting patterns,we classify the bursts into five main categories:downward drifting(263)bursts,upward drifting(3)bursts,complex(203),no drifting(35)bursts,and no evidence for drifting(121)bursts.Subtypes are introduced based on the emission frequency range in the band(low,middle,high and wide)as well as the number of components in one burst(1,2,or multiple).We measured a varying scintillation bandwidth from about 0.5 MHz at 1.0 GHz to 1.4 MHz at 1.5 GHz with a spectral index of 3.0.
基金This project,as one of five key projects,is being carried out by using FAST,a Chinese national mega-science facility built and operated by the National Astronomical Observatories,Chinese Academy of Sciencessupported by the National Natural Science Foundation of China(NSFC,Nos.11988101 and 11833009)+5 种基金the Key Research Program of the Chinese Academy of Sciences(grant No.QYZDJ-SSWSLH021)supported by the Cultivation Project for the FAST scientific Payoff and Research Achievement of CAMS-CASsupported by NSFC No.12133004,partially supported by NSFC No.U1731120partially supported by the NSFC No.11873058,partially supported by NSFC No.U2031115partially supported by the National SKA program of China No.2020SKA0120200partially supported by the Guangzhou Science and Technology Project No.202102010466。
文摘We have carried out the Galactic Plane Pulsar Snapshot(GPPS)survey by using the Five-hundred-meter Aperture Spherical radio Telescope(FAST),the most sensitive systematic pulsar survey in the Galactic plane.In addition to more than 500 pulsars already discovered through normal periodical search,we report here the discovery of 76 new transient radio sources with sporadic strong pulses,detected by using the newly developed module for a sensitive single-pulse search.Their small DM values suggest that they all are Galactic rotating radio transients(RRATs).They show different properties in the follow-up observations.More radio pulses have been detected from 26 transient radio sources but no periods can be found due to a limited small number of pulses from all FAST observations.The followup observations show that 16 transient sources are newly identified as being the prototypes of RRATs with a period already determined from more detected sporadic pulses,and 10 sources are extremely nulling pulsars,and 24 sources are weak pulsars with sparse strong pulses.On the other hand,48 previously known RRATs have been detected by the FAST,either during verification observations for the GPPS survey or through targeted observations of applied normal FAST projects.Except for one RRAT with four pulses detected in a session of 5-minute observation and four RRATs with only one pulse detected in a session,sensitive FAST observations reveal that 43 RRATs are just generally weak pulsars with sporadic strong pulses or simply very nulling pulsars,so that the previously known RRATs always have an extreme emission state together with a normal hardly detectable weak emission state.This is echoed by the two normal pulsars J1938+2213 and J1946+1449 with occasional brightening pulses.Though strong pulses of RRATs are very outstanding in the energy distribution,their polarization angle variations follow the polarization angle curve of the averaged normal pulse profile,suggesting that the predominant sparse pulses of RRATs are emitted in the same region with the same geometry as normal weak pulsars.
基金supported by the National Natural Science Foundation of China(NSFC,grant Nos.11988101 and 11833009),supported by the National Natural Science Foundation of China(NSFC,grant No.U2031115)supported by the National Key R&D Program of China(No.2021YFA1600401 and 2021YFA1600400)+1 种基金National Natural Science Foundation of China(NSFC,grant Nos.11873058 and 12133004)the National SKA program of China(No.2020SKA0120200)。
文摘Pulsar polarization profiles form a very basic database for understanding the emission processes in a pulsar magnetosphere.After careful polarization calibration of the 19-beam L-band receiver and verification of beamoffset observation results,we obtain polarization profiles of 682 pulsars from observations by the Five-hundredmeter Aperture Spherical radio Telescope(FAST)duringthe Galactic Plane Pulsar Snapshot survey and other normal FAST projects.Among them,polarization profiles of about 460 pulsars are observed for the first time.The profiles exhibit diverse features.Some pulsars have a polarization position angle curve with a good S-shaped swing,some with orthogonal modes;some have components with highly linearly polarized components or strong circularly polarized components;some have a very wide profile,coming from an aligned rotator,and some have an interpulse from a perpendicular rotator;some wide profiles are caused by interstellar scattering.We derive geometric parameters for 190 pulsars from the S-shaped position angle curves or with orthogonal modes.We find that the linear and circular polarization or the widths of pulse profiles have various frequency dependencies.Pulsars with a large fraction of linear polarization are more likely to have a large Edot.
基金supported by the National Natural Science Foundation of China(NSFC,Grant Nos.11988101,11833009)the National SKA Program of China(Grant No.2022SKA0120103)+2 种基金the National Key R&D Program of China(Nos.2021YFA1600401 and 2021YFA1600400)the Open Project Program of the Key Laboratory of FAST,NAOC,Chinese Academy of SciencesX.Y.G.acknowledges the financial support from the CAS-NWO cooperation program(Grant No.GJHZ1865)。
文摘Double radio lobes are generally believed to be produced by active nuclei of elliptical galaxies.However,several double-lobed radio sources have been solidly found to be associated with spiral galaxies.By cross-matching~9×105 spiral galaxies selected from the Sloan Digital Sky Survey DR8 data with the full 1.4 GHz radio source catalogs of NRAO VLA Sky Survey and Faint Images of the Radio Sky at Twenty-centimeters,we identify three new spiral galaxies:J0326-0623,J1110+0321 and J1134+3046 that produce double radio lobes,and five doublelobed spirals previously known.By combining the newly discovered and all the other known cases in literature,we confirm the relation that more massive spiral galaxies could produce more powerful radio lobes.We find that most of these spiral galaxies are located in a galaxy group or a poor cluster,in which the environment is denser than in the field,and about half of them are the central brightest galaxies in their parent system.We therefore suggest that the environment is one of the key factors for a spiral to produce double radio lobes.
基金supported by the National Natural Science Foundation of China(Grant Nos.11473034 and 11503038)the Strategic Priority Research Program "The Emergence of Cosmological Structures" of the Chinese Academy of Sciences(Grant No.XDB09010200)
文摘Fast radio bursts show large dispersion measures, much larger than the Galactic dispersion measure foreground. Therefore, they evidently have an extragalac- tic origin. We investigate possible contributions to the dispersion measure from host galaxies. We simulate the spatial distribution of fast radio bursts and calculate the dis- persion measures along the sightlines from fast radio bursts to the edge of host galaxies by using the scaled NE2001 model for thermal electron density distributions. We find that contributions to the dispersion measure of fast radio bursts from the host galaxy follow a skew Gaussian distribution. The peak and the width at half maximum of the dispersion measure distribution increase with the inclination angle of a spiral galaxy, to large values when the inclination angle is over 70~. The largest dispersion measure produced by an edge-on spiral galaxy can reach a few thousand pc cm-3, while the dispersion measures from dwarf galaxies and elliptical galaxies have a maximum of only a few tens of pc cm-3. Notice, however, that additional dispersion measures of tens to hundreds of pc cm-3 can be produced by high density clumps in host galaxies. Simulations that include dispersion measure contributions from the Large Magellanic Cloud and the Andromeda Galaxy are shown as examples to demonstrate how to ex- tract the dispersion measure from the intergalactic medium.
基金the GPPS survey project,as one of five key projects of FAST,a Chinese national mega-science facility,operated by the National Astronomical Observatories,Chinese Academy of Sciencessupported by the National Natural Science Foundation of China(NSFC,Nos.11988101 and 11833009)the Key Research Program of the Chinese Academy of Sciences(grant No.QYZDJ-SSW-SLH021)。
文摘Radio astronomy observations are frequently impacted by radio frequency interference(RFI).We propose a novel method,named 2σCRF,for cleaning RFI in the folded data of pulsar observations,utilizing a Bayesian-based model called conditional random fields(CRFs).This algorithm minimizes the“energy”of every pixel given an initial label.The standard deviations(i.e.,rms values)of the folded pulsar data are utilized as pixels for all subintegrations and channels.Non-RFI data without obvious interference is treated as“background noise,”while RFI-affected data have different classes due to their exceptional rms values.This initial labeling can be automated and is adaptive to the actual data.The CRF algorithm optimizes the label category for each pixel of the image with the prior initial labels.We demonstrate the efficacy of the proposed method on pulsar folded data obtained from Five-hundred-meter Aperture Spherical radio Telescope observations.It can effectively recognize and tag various categories of RFIs,including broadband or narrowband,constant or instantaneous,and even weak RFIs that are unrecognizable in some pixels but picked out based on their neighborhoods.The results are comparable to those obtained via manual labeling but without the need for human intervention,saving time and effort.
基金supported by the National Key R&D Program of China (Nos. 2021YFA1600401 and2021YFA1600400)National Natural Science Foundation of China (Nos. 11873058 and 12133004)supported by the National Natural Science Foundation of China (Nos.11988101 and 11833009)。
文摘Previous studies have identified two emission modes in PSR B1859+07: a normal mode that has three prominent components in the average profile, with the trailing one being the brightest, and an anomalous mode(i.e., the A mode) where emissions seem to be shifted to an earlier phase. Within the normal mode, further analysis has revealed the presence of two submodes, i.e., the cW mode and c B mode, where the central component can appear either weak or bright. As for the anomalous mode, a new bright component emerges in the advanced phase while the bright trailing component in the normal mode disappears. New observations of PSR B1859+07 using the Fivehundred-meter Aperture Spherical Radio Telescope(FAST) have revealed the existence of a previously unknown emission mode, dubbed the Af mode. In this mode, all emission components seen in the normal and anomalous modes are detected. Notably, the mean polarization profiles of both the A and Af modes exhibit a jump in the orthogonal polarization angle modesin the bright leading component. The polarization angles for the central component in the original normal mode follow two distinct orthogonal polarization modes in the A and Af modes respectively. The polarization angles for the trailing component show almost the same but a small systematic shift in the A and Af modes, roughly following the values for the c W and cB modes. Those polarization features of this newly detected emission mode imply that the anomalous mode A of PSR B1859+07 is not a result of “phase shift”or “swooshes” of normal components, but simply a result of the varying intensities of different profile components.Additionally, subpulse drifting has been detected in the leading component of the Af mode.
