We present a wideband polarization analysis of the mode-changing pulsar PSR J1938+2213 using the ultra-wideband low-frequency receiver on Murriyang,the Parkes 64 m radio telescope.Polarization profiles for both the bu...We present a wideband polarization analysis of the mode-changing pulsar PSR J1938+2213 using the ultra-wideband low-frequency receiver on Murriyang,the Parkes 64 m radio telescope.Polarization profiles for both the burst and weak emission modes are obtained.We find that the pulse widths of the two modes exhibit distinct frequency dependencies:the pulse width increases with frequency in the burst mode,but decreases in the weak mode.The linear and circular polarization fractions also show different trends with frequency between the two modes.Our spectral analysis shows that both modes follow power-law spectra,but with differing spectral indices.展开更多
Flux densities are fundamental observational parameters that describe a pulsar.In the current pulsar catalogue,27% of the listed radio pulsars have no flux density measurement in the 20 cm observing band.Here,we prese...Flux densities are fundamental observational parameters that describe a pulsar.In the current pulsar catalogue,27% of the listed radio pulsars have no flux density measurement in the 20 cm observing band.Here,we present the first such measurements for 32 pulsars observed employing the Parkes radio telescope.We have used both archival and new observations to make these measurements.Various schemes exist for measuring flux densities and we show how the measured flux densities vary between these methods and how the presence of radio-frequency interference will bias the flux density measurements.展开更多
Flux densities are basic observation parameters to describe pulsars.In the most updated pulsar catalog,24%of the listed radio pulsars have no flux density measurement at any frequency.Here,we report the first flux den...Flux densities are basic observation parameters to describe pulsars.In the most updated pulsar catalog,24%of the listed radio pulsars have no flux density measurement at any frequency.Here,we report the first flux density measurements,spectral indices,pulse profiles,and correlations of the spectral index with pulsar parameters for 19 pulsars employing the Ultra-Wideband Low receiver system installed on the Parkes radio telescope.The results for spectral indices of 17 pulsars are in the range between-0.6 and-3.10.The polarization profiles of thirteen pulsars are shown.There is a moderate correlation between the spectral index and spin frequency.For most pulsars detected,the signal-to-noise ratio of pulse profile is not high,so DM,Faraday rotation measure,and polarization cannot be determined precisely.Twenty-nine pulsars were not detected in our observations.We discuss the possible explanations for why these pulsars were not detected.展开更多
The Five-hundred-meter Aperture Spherical radio Telescope(FAST) will become one of the world-leading telescopes for pulsar timing array(PTA) research. The primary goals for PTAs are to detect(and subsequently study) u...The Five-hundred-meter Aperture Spherical radio Telescope(FAST) will become one of the world-leading telescopes for pulsar timing array(PTA) research. The primary goals for PTAs are to detect(and subsequently study) ultra-low-frequency gravitational waves, to develop a pulsar-based time standard and to improve solar system planetary ephemerides. FAST will have the sensitivity to observe known pulsars with significantly improved signal-to-noise ratios and will discover a large number of currently unknown pulsars. We describe how FAST will contribute to PTA research and show that jitter-and timing-noise will be the limiting noise processes for FAST data sets. Jitter noise will limit the timing precision achievable over data spans of a few years while timing noise will limit the precision achievable over many years.展开更多
The fast radio burst,FRB 171019,was relatively bright when discovered first by ASKAP but was identified as a repeater with three faint bursts detected later by GBT and CHIME.These observations lead to the discussion o...The fast radio burst,FRB 171019,was relatively bright when discovered first by ASKAP but was identified as a repeater with three faint bursts detected later by GBT and CHIME.These observations lead to the discussion of whether the first bright burst shares the same mechanism with the following repeating bursts.A model of binary neutron star merger is proposed for FRB 171019,in which the first bright burst occurred during the merger event,while the subsequent repeating bursts are starquake-induced,and generally fainter,as the energy release rate for the starquakes can hardly exceed that of the catastrophic merger event.This scenario is consistent with the observation that no later burst detected is as bright as the first one.展开更多
Precise measurements of neutron star(NS)velocities provide critical clues in regard to the supernova physics and evolution of binary systems.Based on Gaia Data Release 2(DR2),we selected a sample of 24 young(<3 Myr...Precise measurements of neutron star(NS)velocities provide critical clues in regard to the supernova physics and evolution of binary systems.Based on Gaia Data Release 2(DR2),we selected a sample of 24 young(<3 Myr)pulsars with precise parallax measurements and measured the velocity of their local standard of rest(LSR)and the velocity dispersion among their respective local stellar groups.The median velocity difference between thus calculated LSRs and the Galactic rotation model is~7.6 km s^(-1),small compared to the typical velocity dispersion of~27.5 km s^(-1).For pulsars off the Galactic plane,such differences grow significantly to as large as~40 km s^(-1).More importantly,the velocity dispersion of stars in the local group of low-velocity pulsars can be comparable to their transverse velocities,suggesting that the intrinsic velocities of NS progenitors should be taken into account when we consider their natal kicks and binary evolution.We also examined the double NS system J0737-3039 A/B,and measured its transverse velocity to be 26-13+18 km s^(-1)assuming nearby Gaia sources are representative of their birth environment.This work demonstrated the feasibility and importance of using Gaia data to study the velocity of individual systems and velocity distribution of NSs.展开更多
Transcontinental e-VLBI observations were conducted in June 2008 with telescopes in Australia, China and Japan. Detections were made of the radio-loud quasar PKS B0727-115, which shows superlu- minal motion, and the i...Transcontinental e-VLBI observations were conducted in June 2008 with telescopes in Australia, China and Japan. Detections were made of the radio-loud quasar PKS B0727-115, which shows superlu- minal motion, and the intra-day variable quasar PKS B0524＋034. The latter source was used as a phase reference calibrator for observations at the position of the gamma-ray burst GRB 080409, for which an upper limit to the radio emission is set. Australia Telescope Compact Array data were also used to derive a limit on the radio flux density of the GRB afterglow. These observations demonstrate the capability to form a large Australasian radio telescope network for e-VLBI, with data transported and processed in realtime over high capacity networks. This campaign represents the first step towards more regular e-VLBI observations in this region.展开更多
In the centenary year of Einstein's General Theory of Relativity, this paper reviews the current status of gravitational wave astronomy across a spectrum which stretches from attohertz to kilohertz frequencies. Se...In the centenary year of Einstein's General Theory of Relativity, this paper reviews the current status of gravitational wave astronomy across a spectrum which stretches from attohertz to kilohertz frequencies. Sect. 1 of this paper reviews the historical development of gravitational wave astronomy from Einstein's first prediction to our current understanding the spectrum. It is shown that detection of signals in the audio frequency spectrum can be expected very soon, and that a north-south pair of next generation detectors would provide large scientific benefits. Sect. 2 reviews the theory of gravitational waves and the principles of detection using laser interferometry. The state of the art Advanced LIGO detectors are then described. These detectors have a high chance of detecting the first events in the near future. Sect. 3 reviews the KAGRA detector currently under development in Japan,which will be the first laser interferometer detector to use cryogenic test masses. Sect. 4 of this paper reviews gravitational wave detection in the nanohertz frequency band using the technique of pulsar timing. Sect. 5 reviews the status of gravitational wave detection in the attohertz frequency band, detectable in the polarisation of the cosmic microwave background, and discusses the prospects for detection of primordial waves from the big bang. The techniques described in sects. 1–5 have already placed significant limits on the strength of gravitational wave sources. Sects. 6 and 7 review ambitious plans for future space based gravitational wave detectors in the millihertz frequency band. Sect. 6 presents a roadmap for development of space based gravitational wave detectors by China while sect. 7 discusses a key enabling technology for space interferometry known as time delay interferometry.展开更多
Giant pulses(GPs) are extremely bright individual pulses of radio pulsar. In microbursts of Crab pulsar, which is an active GP emitter, zebra-pattern-like spectral structures are observed, which are reminiscent of the...Giant pulses(GPs) are extremely bright individual pulses of radio pulsar. In microbursts of Crab pulsar, which is an active GP emitter, zebra-pattern-like spectral structures are observed, which are reminiscent of the "zebra bands" that are observed in type Ⅳ solar radio flares. However, band spacing linearly increases with the band center frequency of ～5-30 GHz. In this study, we propose that the Crab pulsar GP can originate from the coherent instability of plasma near a light cylinder. Further, the growth of coherent instability can be attributed to the resonance observed between the cyclotron-resonant-excited wave and the background plasma oscillation. The particles can be injected into the closed-field line regions owing to magnetic reconnection near a light cylinder. These particles introduce a large amount of free energy that further causes cyclotron-resonant instability, which grows and amplifies radiative waves at frequencies close to the electron cyclotron harmonics that exhibit zebra-pattern-like spectral band structures. Further, these structures can be modulated by the resonance between the cyclotron-resonant-excited wave and the background plasma oscillation. In this scenario, the band structures of the Crab pulsar can be well fitted by a coherent instability model, where the plasma density of a light cylinder should be ～10^(13-15) cm^(-3), with an estimated gradient of >5.5 × 10~5 cm^(-4). This process may be accompanied by high-energy emissions. Similar phenomena are expected to be detected in other types of GP sources that have magnetic fields of ? 106 G in a light cylinder.展开更多
With the largest dish Five-hundred-meter Aperture Spherical radio Telescope(FAST), both the mean and single pulses of PSR B2016+28, especially including the single-pulse structure, are investigated in detail in this s...With the largest dish Five-hundred-meter Aperture Spherical radio Telescope(FAST), both the mean and single pulses of PSR B2016+28, especially including the single-pulse structure, are investigated in detail in this study. The mean pulse profiles at different frequencies can be well fitted in a conal model, and the peak separation of intensity-dependent pulse profiles increases with intensity. The integrated pulses are obviously frequency dependent(pulse width decreases by ～20% as frequency increases from 300 to 750 MHz), but the structure of single pulses changes slightly(the corresponding correlation scale decreases by only～1%). This disparity between mean and single pulses provides independent evidence for the existence of the RS-type vacuum inner gap, indicating a strong bond between particles on the pulsar surface. Diffused drifting sub-pulses are analyzed. The results show that the modulation period along pulse series(P_3) is positively correlated to the separation between two adjacent sub-pulses(P_2). This correlation may hint a rough surface on the pulsar, eventually resulting in the irregular drift of sparks. All the observational results may have significant implications in the dynamics of pulsar magnetosphere and are discussed extensively in this paper.展开更多
基金supported by the National Natural Science Foundation of China(Nos.12288102,12203092,12041304,12403060,12203045,12203093,12163001 and 12463007)the Major Science and Technology Program of Xinjiang Uygur Autonomous Region(Nos.2022A03013-3,and 2022A03013-2)+7 种基金the National SKA Program of China(No.2020SKA0120100)the National Key Research and Development Program of China(Nos.2022YFC2205202 and 2021YFC2203502)the Natural Science Foundation of Xinjiang Uygur Autonomous Region(Nos.2022D01B71 and 2022D01B218)the Tianshan Talent Training Program for Young Elite Scientists(No.2023TSYCQNTJ0024)the 2022 Project Xinjiang Uygur Autonomous Region of China for Tianchi Talents,the open research project funded by the Key Laboratory of Xinjiang Uyghur Autonomous Region(No.2021000059)the National Key Research and Development Program(No.2022YFA1603104)The research is partly supported by the Operation,Maintenance and Upgrading Fund for Astronomical Telescopes and Facility Instruments,budgeted from the Ministry of Finance of China(MOF)and administrated by the Chinese Academy of Sciences(CAS)Murriyang,CSIRO’s Parkes radio telescope,is part of the Australia Telescope National Facility(https://ror.org/05qajvd42)which is funded by the Australian Government for operation as a National Facility managed by CSIRO.
文摘We present a wideband polarization analysis of the mode-changing pulsar PSR J1938+2213 using the ultra-wideband low-frequency receiver on Murriyang,the Parkes 64 m radio telescope.Polarization profiles for both the burst and weak emission modes are obtained.We find that the pulse widths of the two modes exhibit distinct frequency dependencies:the pulse width increases with frequency in the burst mode,but decreases in the weak mode.The linear and circular polarization fractions also show different trends with frequency between the two modes.Our spectral analysis shows that both modes follow power-law spectra,but with differing spectral indices.
基金the National Key R&D Program of China (No. 2017YFA0402602)the Strategic Priority Research Programme (B) of the Chinese Academy of Sciences (No. XDB23010200)
文摘Flux densities are fundamental observational parameters that describe a pulsar.In the current pulsar catalogue,27% of the listed radio pulsars have no flux density measurement in the 20 cm observing band.Here,we present the first such measurements for 32 pulsars observed employing the Parkes radio telescope.We have used both archival and new observations to make these measurements.Various schemes exist for measuring flux densities and we show how the measured flux densities vary between these methods and how the presence of radio-frequency interference will bias the flux density measurements.
基金the National Natural Science Foundation of China(Grant No.NSFC12041304)National SKA Program of China(No.2020SKA0120100)+3 种基金Youth Innovation Promotion Association of Chinese Academy of SciencesNational Key Research and Development Program of China(No.2017YFA0402602)the CAS Jianzhihua projectHeaven Lake Hundred-Talent Program of Xinjiang Uygur Autonomous Region of China。
文摘Flux densities are basic observation parameters to describe pulsars.In the most updated pulsar catalog,24%of the listed radio pulsars have no flux density measurement at any frequency.Here,we report the first flux density measurements,spectral indices,pulse profiles,and correlations of the spectral index with pulsar parameters for 19 pulsars employing the Ultra-Wideband Low receiver system installed on the Parkes radio telescope.The results for spectral indices of 17 pulsars are in the range between-0.6 and-3.10.The polarization profiles of thirteen pulsars are shown.There is a moderate correlation between the spectral index and spin frequency.For most pulsars detected,the signal-to-noise ratio of pulse profile is not high,so DM,Faraday rotation measure,and polarization cannot be determined precisely.Twenty-nine pulsars were not detected in our observations.We discuss the possible explanations for why these pulsars were not detected.
基金support from the Australian Research Council (ARC) Future Fellowship programmesupport from the National Natural Science Foundation of China (11225314)
文摘The Five-hundred-meter Aperture Spherical radio Telescope(FAST) will become one of the world-leading telescopes for pulsar timing array(PTA) research. The primary goals for PTAs are to detect(and subsequently study) ultra-low-frequency gravitational waves, to develop a pulsar-based time standard and to improve solar system planetary ephemerides. FAST will have the sensitivity to observe known pulsars with significantly improved signal-to-noise ratios and will discover a large number of currently unknown pulsars. We describe how FAST will contribute to PTA research and show that jitter-and timing-noise will be the limiting noise processes for FAST data sets. Jitter noise will limit the timing precision achievable over data spans of a few years while timing noise will limit the precision achievable over many years.
基金supported by the Australian National Data Service(ANDS).ANDS is supported by the Australian Government through the National Collaborative Research Infrastructure Strategy Program and the Education Investment Fund(EIF)Super Science Initiative 19the UK's AstroGrid Virtual Observatory Project,which is funded by the Science and Technology Facilities Council andthrough the EU's Framework 6 programme+1 种基金part of the Australia Telescope,whichis funded by the Commonwealth of Australia for operation as a National Facility managed by the Commonwealth Scientific and Industrial Research Organisation(CSIRO)GH is the recipient of an Australian Research CouncilQEII Fellowship(#DP0878388)
基金as part of the Parkes Pulsar Timing Array projectThe Parkesradio telescope is part of the Australia Telescope which is funded by the Commonwealth of Australia for operationas a National Facility managed by CSIRO+1 种基金GH is the recipient of an Australian Research Council QEII Fellowship(project#DP0878388)support from the Chinese Academy of Sciences#CAS KJCX2-YW-T09and NSFC 10803006
基金supported by the Mo ST Grant(2016YFE0100300)the National Key R&D Program of China(2017YFA0402602)+2 种基金NSFC(11633004,11473044,11653003,11673002 and U1531243)the Strategic Priority Research Program of CAS(XDB23010200)the CAS grants(QYZDJSSW-SLH017 and CAS XDB 23040100)。
文摘The fast radio burst,FRB 171019,was relatively bright when discovered first by ASKAP but was identified as a repeater with three faint bursts detected later by GBT and CHIME.These observations lead to the discussion of whether the first bright burst shares the same mechanism with the following repeating bursts.A model of binary neutron star merger is proposed for FRB 171019,in which the first bright burst occurred during the merger event,while the subsequent repeating bursts are starquake-induced,and generally fainter,as the energy release rate for the starquakes can hardly exceed that of the catastrophic merger event.This scenario is consistent with the observation that no later burst detected is as bright as the first one.
基金supported by the National Natural Science Foundation of China(Grant Nos.11988101,11725313 and U2031121)Funding for the DPAC has been provided by national institutions,in particular the institutions participating in the Gaia Multilateral AgreementS.D.is the recipient of an Australian Research Council Discovery Early Career Award(DE210101738)funded by the Australian Government。
文摘Precise measurements of neutron star(NS)velocities provide critical clues in regard to the supernova physics and evolution of binary systems.Based on Gaia Data Release 2(DR2),we selected a sample of 24 young(<3 Myr)pulsars with precise parallax measurements and measured the velocity of their local standard of rest(LSR)and the velocity dispersion among their respective local stellar groups.The median velocity difference between thus calculated LSRs and the Galactic rotation model is~7.6 km s^(-1),small compared to the typical velocity dispersion of~27.5 km s^(-1).For pulsars off the Galactic plane,such differences grow significantly to as large as~40 km s^(-1).More importantly,the velocity dispersion of stars in the local group of low-velocity pulsars can be comparable to their transverse velocities,suggesting that the intrinsic velocities of NS progenitors should be taken into account when we consider their natal kicks and binary evolution.We also examined the double NS system J0737-3039 A/B,and measured its transverse velocity to be 26-13+18 km s^(-1)assuming nearby Gaia sources are representative of their birth environment.This work demonstrated the feasibility and importance of using Gaia data to study the velocity of individual systems and velocity distribution of NSs.
文摘Transcontinental e-VLBI observations were conducted in June 2008 with telescopes in Australia, China and Japan. Detections were made of the radio-loud quasar PKS B0727-115, which shows superlu- minal motion, and the intra-day variable quasar PKS B0524＋034. The latter source was used as a phase reference calibrator for observations at the position of the gamma-ray burst GRB 080409, for which an upper limit to the radio emission is set. Australia Telescope Compact Array data were also used to derive a limit on the radio flux density of the GRB afterglow. These observations demonstrate the capability to form a large Australasian radio telescope network for e-VLBI, with data transported and processed in realtime over high capacity networks. This campaign represents the first step towards more regular e-VLBI observations in this region.
基金supported by the US National Science Foundation(Grant No.PHY-0757058)supported by the National Natural Science Foundation of China(Grant Nos.11443008 and 11503003)+2 种基金a Returned Overseas Chinese Scholars Foundation grant,and Fundamental Research Funds for the Central Universities(Grant No.2015KJJCB06)supported by the National Space Science Center,Chinese Academy of Sciences(Grant Nos.XDA04070400 and XDA04077700)Partial supports from the National Natural Science Foundation of China(Grant Nos.11305255,11171329 and 41404019)
文摘In the centenary year of Einstein's General Theory of Relativity, this paper reviews the current status of gravitational wave astronomy across a spectrum which stretches from attohertz to kilohertz frequencies. Sect. 1 of this paper reviews the historical development of gravitational wave astronomy from Einstein's first prediction to our current understanding the spectrum. It is shown that detection of signals in the audio frequency spectrum can be expected very soon, and that a north-south pair of next generation detectors would provide large scientific benefits. Sect. 2 reviews the theory of gravitational waves and the principles of detection using laser interferometry. The state of the art Advanced LIGO detectors are then described. These detectors have a high chance of detecting the first events in the near future. Sect. 3 reviews the KAGRA detector currently under development in Japan,which will be the first laser interferometer detector to use cryogenic test masses. Sect. 4 of this paper reviews gravitational wave detection in the nanohertz frequency band using the technique of pulsar timing. Sect. 5 reviews the status of gravitational wave detection in the attohertz frequency band, detectable in the polarisation of the cosmic microwave background, and discusses the prospects for detection of primordial waves from the big bang. The techniques described in sects. 1–5 have already placed significant limits on the strength of gravitational wave sources. Sects. 6 and 7 review ambitious plans for future space based gravitational wave detectors in the millihertz frequency band. Sect. 6 presents a roadmap for development of space based gravitational wave detectors by China while sect. 7 discusses a key enabling technology for space interferometry known as time delay interferometry.
基金supported by the China Program of International ST Cooperation 2016YFE 0100300the National Natural Science Foundation of China (Grant Nos. 11473044, 11633004, and 11653003)+10 种基金the Chinese Academy of Sciences (Grant No. QYZDJ-SSW-SLH017)supported by the the National Natural Science Foundation of China (Grant No. 11225314)the Open Project Program of the Key Laboratory of Radio Astronomy, Chinese Academy of Sciencessupported by the National Natural Science Foundation of China (Grant No. U15311243)the National Basic Research Program of China (Grant Nos. 2015CB857101, XDB23010200, 11690024, 11373011)the Max-Planck Partner Groupsupported by the National Key R&D Program of China (Grant No. 2017YFA0402602)the National Natural Science Foundation of China (Grant Nos. 11673002, and U1531243)the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB23010200)supported by the National Natural Science Foundation of China (Grant Nos. 11573039, 11661161015, and 11790301)supported by the Special Funding for Advanced Users, budgeted and administrated by Center for Astronomical Mega-Science, Chinese Academy of Sciences (CAMS)
文摘Giant pulses(GPs) are extremely bright individual pulses of radio pulsar. In microbursts of Crab pulsar, which is an active GP emitter, zebra-pattern-like spectral structures are observed, which are reminiscent of the "zebra bands" that are observed in type Ⅳ solar radio flares. However, band spacing linearly increases with the band center frequency of ～5-30 GHz. In this study, we propose that the Crab pulsar GP can originate from the coherent instability of plasma near a light cylinder. Further, the growth of coherent instability can be attributed to the resonance observed between the cyclotron-resonant-excited wave and the background plasma oscillation. The particles can be injected into the closed-field line regions owing to magnetic reconnection near a light cylinder. These particles introduce a large amount of free energy that further causes cyclotron-resonant instability, which grows and amplifies radiative waves at frequencies close to the electron cyclotron harmonics that exhibit zebra-pattern-like spectral band structures. Further, these structures can be modulated by the resonance between the cyclotron-resonant-excited wave and the background plasma oscillation. In this scenario, the band structures of the Crab pulsar can be well fitted by a coherent instability model, where the plasma density of a light cylinder should be ～10^(13-15) cm^(-3), with an estimated gradient of >5.5 × 10~5 cm^(-4). This process may be accompanied by high-energy emissions. Similar phenomena are expected to be detected in other types of GP sources that have magnetic fields of ? 106 G in a light cylinder.
基金supported by the National Key R&D Program of China(Grant Nos.2018YFA0404703,and 2017YFA0402602)the National Natural Science Foundation of China(Grant Nos.11673002,and 11225314)+5 种基金the Open Project Program of the Key Laboratory of FAST,National Astronomical Observatories,Chinese Academy of Sciencesthe project of Chinese Academy of Sciences(CAS)supported by the Special Funding for Advanced Users,budgeted and administrated by Center for Astronomical Mega-Science,Chinese Academy of Sciences(CAMS)Chinese Academy of Sciences "Light of West China" Programthe Max-Planck-Society(MPS)collaborationsupported by the National Key R&D Program of China(Grant No.2017YFA0402600)
文摘With the largest dish Five-hundred-meter Aperture Spherical radio Telescope(FAST), both the mean and single pulses of PSR B2016+28, especially including the single-pulse structure, are investigated in detail in this study. The mean pulse profiles at different frequencies can be well fitted in a conal model, and the peak separation of intensity-dependent pulse profiles increases with intensity. The integrated pulses are obviously frequency dependent(pulse width decreases by ～20% as frequency increases from 300 to 750 MHz), but the structure of single pulses changes slightly(the corresponding correlation scale decreases by only～1%). This disparity between mean and single pulses provides independent evidence for the existence of the RS-type vacuum inner gap, indicating a strong bond between particles on the pulsar surface. Diffused drifting sub-pulses are analyzed. The results show that the modulation period along pulse series(P_3) is positively correlated to the separation between two adjacent sub-pulses(P_2). This correlation may hint a rough surface on the pulsar, eventually resulting in the irregular drift of sparks. All the observational results may have significant implications in the dynamics of pulsar magnetosphere and are discussed extensively in this paper.
