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
We report the radio observations of the eclipsing black widow pulsar J1720-0534, a 3.26 ms pulsar in orbit with a low mass companion of mass 0.029 to 0.034 M⊙. We obtain the phase-connected timing ephemeris and polar...We report the radio observations of the eclipsing black widow pulsar J1720-0534, a 3.26 ms pulsar in orbit with a low mass companion of mass 0.029 to 0.034 M⊙. We obtain the phase-connected timing ephemeris and polarization profile of this millisecond pulsar(MSP) using the Five-hundred-meter Aperture Spherical radio Telescope(FAST), the Green Bank Telescope(GBT), and the Parkes Telescope. For the first time from such a system, an oscillatory polarization angle change was observed from a particular eclipse egress with partial depolarization, indicating 10-milliGauss-level reciprocating magnetic fields oscillating in a length scale of 5 ×10^(3)km(assuming an orbital inclination angle of 90°) outside the companion's magnetosphere. The dispersion measure variation observed during the ingresses and egresses shows the rapid raising of the electron density in the shock boundary between the companion's magnetosphere and the surrounding pulsar wind. We suggest that the observed oscillatory magnetic fields originate from the pulsar wind outside the companion's magnetosphere.展开更多
PSR J0742-2822 is known for its quasi-periodic changes in the observed pulse profile and spindown rate.In this paper,we analyzed 13 years of timing data obtained with the Nanshan 25-m radio telescope and the Parkes 64...PSR J0742-2822 is known for its quasi-periodic changes in the observed pulse profile and spindown rate.In this paper,we analyzed 13 years of timing data obtained with the Nanshan 25-m radio telescope and the Parkes 64-m radio telescope.We found that the average values of the spin-down rate((v))of this pulsar changed in four different states.We investigated the correlation between v and W50,and ascertained that the correlation changed in different states.Moreover,not all the changes in states and correlation can be associated with glitch activities.We examined the long term evolution ofγ-ray flux(0.1-300 GeV)and the pulse profiles corresponding to the four different states using Fermi-LAT Pass8(P8 R3)data from 2008 August 5 to 2019 October 1.We did not detect a significant change inγ-ray flux or the pulse profile.Our results suggest that the connection between pulsar rotation and emission is more complex than previously reported for this pulsar.展开更多
In this paper,we presented the 23.3 yr of pulsar timing results of PSR J1456-6413 based on the observations of Parkes 64 m radio telescope.We detected two new glitches at MJD 57093(3)and 59060(12)and confirmed its fir...In this paper,we presented the 23.3 yr of pulsar timing results of PSR J1456-6413 based on the observations of Parkes 64 m radio telescope.We detected two new glitches at MJD 57093(3)and 59060(12)and confirmed its first glitch at MJD 54554(10).The relative sizes(Δν/ν)of these two new glitches are 0.9×10^(-9)and 1.16×10^(-9),respectively.Using the“Cholesky”timing analysis method,we have determined its position,proper motion,and two-dimensional transverse velocities from the data segments before and after the second glitch,respectively.Furthermore,we detected exponential recovery behavior after the first glitch,with a recovery timescale of approximately 200 days and a corresponding exponential recovery factor Q of approximately 0.15(2),while no exponential recovery was detected for the other two glitches.More interestingly,we found that the leading component of the integral pulse profile after the second glitch became stronger,while the main component became weaker.Our results will expand the sample of pulsars with magnetosphere fluctuation triggered by the glitch event.展开更多
Pulsar timing measurements with a 26 m radio telescope at Nanshan between 2000 and 2014 were used to search for glitch events. The data span of nine pulsars ranges from 11.6 to 14.2 yr, and 16 new glitch events were i...Pulsar timing measurements with a 26 m radio telescope at Nanshan between 2000 and 2014 were used to search for glitch events. The data span of nine pulsars ranges from 11.6 to 14.2 yr, and 16 new glitch events were identified in nine pulsars. Glitch parameters were determined through fitting the timing residuals data. All 16 glitches have a small fractional size. Six new glitches have been detected in PSR J1833-0827, making it another frequent glitching pulsar. Some of the 16 glitches may experience exponential or linear recovery, but it is unlikely for us to make further analyses with the large gap in the data set. All the glitch rates obtained from Nanshan are higher than that from Jodrell Bank Observatory. The small glitch size and high glitch rate could possibly attribute to the high observation cadence.展开更多
In this paper,we present the Five-hundred-meter Aperture Spherical radio Telescope(FAST)observations of PSRs B1929+10 and B1842+14.Through analysis of the pulsars’scintillation pattern,we detected the known scintilla...In this paper,we present the Five-hundred-meter Aperture Spherical radio Telescope(FAST)observations of PSRs B1929+10 and B1842+14.Through analysis of the pulsars’scintillation pattern,we detected the known scintillation arc from PSR B1929+10 and two previously undetected scintillation arcs from B1842+14.We find that the B1929+10 arc’s curvature scales with observing frequency asη-∝ν-2.1±0.1 andη+∝ν-1.8±0.2,consistent with Arecibo results and the theoretical expectations ofη∝ν-2.From the arc curvature,we infer the scattering screen to be located at 0.20±0.02 kpc from the Earth,close to what was measured by RadioAstron at 324 MHz.From B1842+14,we find two scintillation arcs for the first time.The arcs’curvatures imply that they are caused by two scattering screens located at a distance of 0.3±0.2 kpc and 1.6±0.6 kpc from the Earth,respectively.The screen distance uncertainties mainly come from the uncertainty in pulsar’s dispersion measure(DM)-derived distance.We present these FAST scintillation observations and discuss the future prospect of FAST pulsar scintillation study.展开更多
PSR B0540-69 has a braking index measurement in its persistent state： n = 2.129± 0.012. Recently, it has been reported to have changes in its spin-down state： a sudden 36% increase in the spin- down rate. Combi...PSR B0540-69 has a braking index measurement in its persistent state： n = 2.129± 0.012. Recently, it has been reported to have changes in its spin-down state： a sudden 36% increase in the spin- down rate. Combining the persistent state braking index measurement with different spin-down states, PSR B0540-69 is more powerful than intermittent pulsars in constraining pulsar spin-down models. The pulsar wind model is applied to explain the variable timing behavior of PSR B0540-69. The braking index of PSR B0540-69 in its persistent state results from the combined effect of magnetic dipole radiation and particle wind. The particle density reflects the magnetospheric activity in real-time and may be responsible for the changing spin-down behavior. Corresponding to the 36% increase in the spin-down rate of PSR B0540-69, the relative increase in the particle density is 88% in the vacuum gap model. The braking index calculated with the model in the new state is n = 1.79. Future observations that measure the braking index of PSR B0540-69 in the new spin-down state will be very powerful in distinguishing between different pulsar spin-down models and different particle acceleration models in the wind braking scenario. The variable timing behavior of PSR J 1846-0258 is also understandable in the pulsar wind model.展开更多
Hashtag recommendation for microblogs is a very hot research topic that is useful to many applications involving microblogs. However, since short text in microblogs and low utilization rate of hashtags will lead to th...Hashtag recommendation for microblogs is a very hot research topic that is useful to many applications involving microblogs. However, since short text in microblogs and low utilization rate of hashtags will lead to the data sparsity problem, it is difficult for typical hashtag recommendation methods to achieve accurate recommendation. In light of this, we propose HRMF, a hashtag recommendation method based on multi-features of microblogs in this article. First, our HRMF expands short text into long text, and then it simultaneously models multi-features (i.e., user, hashtag, text) of microblogs by designing a new topic model. To further alleviate the data sparsity problem, HRMF exploits hashtags of both similar users and similar microblogs as the candidate hashtags. In particular, to find similar users, HRMF combines the designed topic model with typical user-based collaborative filtering method. Finally, we realize hashtag recommendation by calculating the recommended score of each hashtag based on the generated topical representations of multi-features. Experimental results on a real-world dataset crawled from Sina Weibo demonstrate the effectiveness of our HRMF for hashtag recommendation.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 Parkes Radio Telescope (Murriyang) is part of the Australia Telescope National Facility, which is funded by the Australian Government for operation as a National Facility managed by CSIROsupported by the National Natural Science Foundation of China (NSFC) grant Nos. 12041303, 12041304, 11873067, 12133004, 12203045, 12203070, 12203072, 12103013, U2031117 and T2241020+11 种基金the CAS-MPG LEGACY project and the National SKA Program of China No. 2020SKA0120200the Foundation of Science and Technology of Guizhou Province No. ((2021)023)the Foundation of Guizhou Provincial Education Department (No.KY(2021)303)the National Key Research and Development Program of China Nos. 2022YFC2205202 and 2022YFC2205203the Major Science and Technology Program of Xinjiang Uygur Autonomous Region Nos. 2022A03013-1, 2022A03013-3 and 2022A03013-4the National Key Research and Development Program of China No. 2022YFC2205203the 2021 project Xinjiang Uygur autonomous region of China for Tianshan elites and the Youth Innovation Promotion Association of CAS under No. 2023069support from the Youth Innovation Promotion Association CAS (id. 2021055)CAS Project for Young Scientists in Basic Research (grant YSBR-006)the Cultivation Project for FAST Scientific Payoff and Research Achievement of CAMS-CASsupport from Zhejiang Provincial Natural Science Foundation of China under grant No. LY23A030001supported by the NSF Physics Frontiers Center award number 2020265。
文摘We report the radio observations of the eclipsing black widow pulsar J1720-0534, a 3.26 ms pulsar in orbit with a low mass companion of mass 0.029 to 0.034 M⊙. We obtain the phase-connected timing ephemeris and polarization profile of this millisecond pulsar(MSP) using the Five-hundred-meter Aperture Spherical radio Telescope(FAST), the Green Bank Telescope(GBT), and the Parkes Telescope. For the first time from such a system, an oscillatory polarization angle change was observed from a particular eclipse egress with partial depolarization, indicating 10-milliGauss-level reciprocating magnetic fields oscillating in a length scale of 5 ×10^(3)km(assuming an orbital inclination angle of 90°) outside the companion's magnetosphere. The dispersion measure variation observed during the ingresses and egresses shows the rapid raising of the electron density in the shock boundary between the companion's magnetosphere and the surrounding pulsar wind. We suggest that the observed oscillatory magnetic fields originate from the pulsar wind outside the companion's magnetosphere.
基金supported by the National Key Research and Development Program of China(2016YFA0400804,2017YFA0402602,2018YFA0404603 and 2018YFA0404703)the Operation,Maintenance and Upgrading Fund for Astronomical Telescopes and Facility Instruments,budgeted from the Ministry of Finance of China(MOF)and administered by the Chinese Academy of Sciences(CAS),the National Natural Science Foundation of China(Grant Nos.11873080,U1831102,U1731238,U1938109,U1838104,11873040,11573010,11661161010,U1631103 and U1838102)+4 种基金the Youth Innovation Promotion Association of Chinese Academy of Sciences,the CAS“Light of West China”Program(Nos.2018-XBQNXZ-B-023,2018-XBQNXZ-B-025 and 2016-QNXZ-B-24)the Tianshan Youth Program No.2018Q039the Open Project Program of the Key Laboratory of FAST,NAOC,Chinese Academy of Sciences,the China Postdoctoral Science Foundation grant(2019M650847)the 2016 and 2018 Project of Xinjiang Uygur Autonomous Region of China for Flexibly Fetching in Upscale Talents and the Science and Technology Fund of Guizhou Province(Grant Nos.(2016)–4008 and(2017)5726–37)part of the Australia Telescope National Facility which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO。
文摘PSR J0742-2822 is known for its quasi-periodic changes in the observed pulse profile and spindown rate.In this paper,we analyzed 13 years of timing data obtained with the Nanshan 25-m radio telescope and the Parkes 64-m radio telescope.We found that the average values of the spin-down rate((v))of this pulsar changed in four different states.We investigated the correlation between v and W50,and ascertained that the correlation changed in different states.Moreover,not all the changes in states and correlation can be associated with glitch activities.We examined the long term evolution ofγ-ray flux(0.1-300 GeV)and the pulse profiles corresponding to the four different states using Fermi-LAT Pass8(P8 R3)data from 2008 August 5 to 2019 October 1.We did not detect a significant change inγ-ray flux or the pulse profile.Our results suggest that the connection between pulsar rotation and emission is more complex than previously reported for this pulsar.
基金supported by the National SKA Program of China(Nos.2022SKA0130100,2020SKA0120100 and 2022SKA0130104)Guizhou Province Science and Technology Foundation(No.ZK[2022]304)+9 种基金the Major Science and Technology Program of Xinjiang Uygur Autonomous Region(Nos.2022A03013-2 and 2022A03013-4)the Scientific Research Project of the Guizhou Provincial Education(Nos.KY[2022]132,KY[2022]123 and KY[2022]137)the National Natural Science Foundation of China(Nos.11873080,U1731238,11565010,12103013,U1838109,U1831120,12273008 and 12103013)the Joint Research Fund in Astronomy under cooperative agreement between the National Natural Science Foundation of China and Chinese Academy of Sciences(No.U1931101)the Foundation of Guizhou Provincial Education Department(Nos.KY(2020)003 and KY(2021)303)the Guizhou Province Science and Technology Support Program(No.[2023]General 333)the 2021 project Xinjiang Uygur autonomous region of China for Tianshan elites,the Key Laboratory of Xinjiang Uygur Autonomous Region No.2020D04049the Academic New Seeding Fund Project of Guizhou Normal University(No.[2022]B18)the CAS Jianzhihua projectThe Parkes radio telescope is part of the Australia Telescope National Facility which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO。
文摘In this paper,we presented the 23.3 yr of pulsar timing results of PSR J1456-6413 based on the observations of Parkes 64 m radio telescope.We detected two new glitches at MJD 57093(3)and 59060(12)and confirmed its first glitch at MJD 54554(10).The relative sizes(Δν/ν)of these two new glitches are 0.9×10^(-9)and 1.16×10^(-9),respectively.Using the“Cholesky”timing analysis method,we have determined its position,proper motion,and two-dimensional transverse velocities from the data segments before and after the second glitch,respectively.Furthermore,we detected exponential recovery behavior after the first glitch,with a recovery timescale of approximately 200 days and a corresponding exponential recovery factor Q of approximately 0.15(2),while no exponential recovery was detected for the other two glitches.More interestingly,we found that the leading component of the integral pulse profile after the second glitch became stronger,while the main component became weaker.Our results will expand the sample of pulsars with magnetosphere fluctuation triggered by the glitch event.
基金supported by the National SKA Program of China(No.2020SKA0120100)the National Natural Science Foundation of China (NSFC+3 种基金No.12041304)Youth Innovation Promotion Association of the Chinese Academy of Sciencesthe CAS Jianzhihua project,Guizhou Provincial Science and Technology Foundation (No.ZK2022304)Heaven Lake Hundred-Talent Program of Xinjiang Uygur Autonomous Region of China。
文摘Pulsar timing measurements with a 26 m radio telescope at Nanshan between 2000 and 2014 were used to search for glitch events. The data span of nine pulsars ranges from 11.6 to 14.2 yr, and 16 new glitch events were identified in nine pulsars. Glitch parameters were determined through fitting the timing residuals data. All 16 glitches have a small fractional size. Six new glitches have been detected in PSR J1833-0827, making it another frequent glitching pulsar. Some of the 16 glitches may experience exponential or linear recovery, but it is unlikely for us to make further analyses with the large gap in the data set. All the glitch rates obtained from Nanshan are higher than that from Jodrell Bank Observatory. The small glitch size and high glitch rate could possibly attribute to the high observation cadence.
基金supported by the CAS“Light of West China”Program 2017-XBQNXZ-B-022the“Tianchi Doctoral Program 2017”+4 种基金the CAS International Partnership Program(No.114A11KYSB20160008)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB23000000)supported by the National Natural Science Foundation of China(Grant Nos.61472043,11743002,11873067,11690024,11725313 and U1831104)supported by the Chinese Academy of Science Pioneer Hundred Talents Programsupported by Special Funding for Advanced Users,budgeted and administrated by Center for Astronomical MegaScience,Chinese Academy of Sciences(CAMS)
文摘In this paper,we present the Five-hundred-meter Aperture Spherical radio Telescope(FAST)observations of PSRs B1929+10 and B1842+14.Through analysis of the pulsars’scintillation pattern,we detected the known scintillation arc from PSR B1929+10 and two previously undetected scintillation arcs from B1842+14.We find that the B1929+10 arc’s curvature scales with observing frequency asη-∝ν-2.1±0.1 andη+∝ν-1.8±0.2,consistent with Arecibo results and the theoretical expectations ofη∝ν-2.From the arc curvature,we infer the scattering screen to be located at 0.20±0.02 kpc from the Earth,close to what was measured by RadioAstron at 324 MHz.From B1842+14,we find two scintillation arcs for the first time.The arcs’curvatures imply that they are caused by two scattering screens located at a distance of 0.3±0.2 kpc and 1.6±0.6 kpc from the Earth,respectively.The screen distance uncertainties mainly come from the uncertainty in pulsar’s dispersion measure(DM)-derived distance.We present these FAST scintillation observations and discuss the future prospect of FAST pulsar scintillation study.
基金supported by the West Light Foundation of CAS(LHXZ 201201)the 973 Program(2015CB857100)Qing Cu Hui of CAS
文摘PSR B0540-69 has a braking index measurement in its persistent state： n = 2.129± 0.012. Recently, it has been reported to have changes in its spin-down state： a sudden 36% increase in the spin- down rate. Combining the persistent state braking index measurement with different spin-down states, PSR B0540-69 is more powerful than intermittent pulsars in constraining pulsar spin-down models. The pulsar wind model is applied to explain the variable timing behavior of PSR B0540-69. The braking index of PSR B0540-69 in its persistent state results from the combined effect of magnetic dipole radiation and particle wind. The particle density reflects the magnetospheric activity in real-time and may be responsible for the changing spin-down behavior. Corresponding to the 36% increase in the spin-down rate of PSR B0540-69, the relative increase in the particle density is 88% in the vacuum gap model. The braking index calculated with the model in the new state is n = 1.79. Future observations that measure the braking index of PSR B0540-69 in the new spin-down state will be very powerful in distinguishing between different pulsar spin-down models and different particle acceleration models in the wind braking scenario. The variable timing behavior of PSR J 1846-0258 is also understandable in the pulsar wind model.
基金supported by the National Natural Science Foundation of China under Grant Nos.61320106006,61532006,61772083,and 61502042the Fundamental Research Funds for the Central Universities of China under Grant No.2017RC39.
文摘Hashtag recommendation for microblogs is a very hot research topic that is useful to many applications involving microblogs. However, since short text in microblogs and low utilization rate of hashtags will lead to the data sparsity problem, it is difficult for typical hashtag recommendation methods to achieve accurate recommendation. In light of this, we propose HRMF, a hashtag recommendation method based on multi-features of microblogs in this article. First, our HRMF expands short text into long text, and then it simultaneously models multi-features (i.e., user, hashtag, text) of microblogs by designing a new topic model. To further alleviate the data sparsity problem, HRMF exploits hashtags of both similar users and similar microblogs as the candidate hashtags. In particular, to find similar users, HRMF combines the designed topic model with typical user-based collaborative filtering method. Finally, we realize hashtag recommendation by calculating the recommended score of each hashtag based on the generated topical representations of multi-features. Experimental results on a real-world dataset crawled from Sina Weibo demonstrate the effectiveness of our HRMF for hashtag recommendation.
