Fast radio bursts(FRBs)are short pulses observed in radio frequencies usually originating from cosmological distances.The discovery of FRB 200428 and its X-ray counterpart from the Galactic magnetar SGR J1935+2154sugg...Fast radio bursts(FRBs)are short pulses observed in radio frequencies usually originating from cosmological distances.The discovery of FRB 200428 and its X-ray counterpart from the Galactic magnetar SGR J1935+2154suggests that at least some FRBs can be generated by magnetars.However,the majority of X-ray bursts from magnetars are not associated with radio emission.The fact that only in rare cases can an FRB be generated raises the question regarding the special triggering mechanism of FRBs.Here we report long time spin evolution of SGR J1935+2154 until the end of 2022.According to v and v,the spin evolution of SGR J1935+2154 could be divided into two stages.The first stage evolves relatively steady evolution until 2020 April 27.After the burst activity in2020,the spin of SGR J1935+2154 shows strong variations,especially for v.After the burst activity in 2022October,a new spin-down glitch with△v/v=(-7.2±0.6)×10^(-6)is detected around MJD 59876,which is the second event in SGR J1935+2154.At the end,spin frequency and pulse profile do not show variations around the time of FRB 200428 and radio bursts 221014 and 221021,which supply strong clues to constrain the trigger mechanism of FRBs or radio bursts.展开更多
Pulsar timing is a classic technology of detecting irregularities in pulsar rotation.We carried out this method for 18 young radio pulsars,with long-term timing observations obtained between 2007 and 2015 using the Pa...Pulsar timing is a classic technology of detecting irregularities in pulsar rotation.We carried out this method for 18 young radio pulsars,with long-term timing observations obtained between 2007 and 2015 using the Parkes 64-m radio telescope.As a result,30 glitches were identified,ranging from 0.75 × 10^(-9) to 8.6 × 10^(-6) in the relative glitch sizes Δv/v,where v=1/P is the pulse frequency.These glitches are composed of 26 new glitches and four published glitches with new exponential recoveries.All pulsars exhibit normal glitches,and six pulsars were observed to undergo a glitch event for the first time.We discuss the properties and implications for neutron-star physics of these glitches,and show that they are in agreement with previous work,except that the cumulative probability distributions of the mean waiting times for PSRs J0537-6910,J1341-6220 and J1740-3015 are not in consonance with the Poisson model.展开更多
In this paper,the Joule–Thomson expansion of the higher dimensional nonlinearly anti-de Sitter(Ad S)black hole with power Maxwell invariant source is investigated.The results show the Joule–Thomson coefficient has a...In this paper,the Joule–Thomson expansion of the higher dimensional nonlinearly anti-de Sitter(Ad S)black hole with power Maxwell invariant source is investigated.The results show the Joule–Thomson coefficient has a zero point and a divergent point,which coincide with the inversion temperature Tiand the zero point of the Hawking temperature,respectively.The inversion temperature increases monotonously with inversion pressure.For the high-pressure region,the inversion temperature decreases with the dimensionality D and the nonlinearity parameter s,whereas it increases with the charge Q.However,Tifor the low-pressure region increase with D and s,while it decreases with Q.The ratioηBHbetween the minimum inversion temperature and the critical temperature does not depend on Q,it recovers the higher dimensional Reissner–N?rdstrom Ad S black hole case when s=1.However,for s>1,it becomes smaller and smaller as D increases and approaches a constant when D→∞.Finally,we found that an increase of mass M and s,or reducing the charge Q and D can enhance the isenthalpic curve,and the effect of s on the isenthalpic curve is much greater than other parameters.展开更多
基金supported by the National Key R&D Program of China(2021YFA0718500)from the Minister of Science and Technology of China(MOST)supports from the National Natural Science Foundation of China under grants 12173103,12003028,U2038101,U2038102 and 11733009+2 种基金supported by International Partnership Program of Chinese Academy of Sciences(grant No.113111KYSB20190020)the National SKA Program of China(2022SKA0130100)the China Manned Spaced Project(CMS-CSST-2021-B11)。
文摘Fast radio bursts(FRBs)are short pulses observed in radio frequencies usually originating from cosmological distances.The discovery of FRB 200428 and its X-ray counterpart from the Galactic magnetar SGR J1935+2154suggests that at least some FRBs can be generated by magnetars.However,the majority of X-ray bursts from magnetars are not associated with radio emission.The fact that only in rare cases can an FRB be generated raises the question regarding the special triggering mechanism of FRBs.Here we report long time spin evolution of SGR J1935+2154 until the end of 2022.According to v and v,the spin evolution of SGR J1935+2154 could be divided into two stages.The first stage evolves relatively steady evolution until 2020 April 27.After the burst activity in2020,the spin of SGR J1935+2154 shows strong variations,especially for v.After the burst activity in 2022October,a new spin-down glitch with△v/v=(-7.2±0.6)×10^(-6)is detected around MJD 59876,which is the second event in SGR J1935+2154.At the end,spin frequency and pulse profile do not show variations around the time of FRB 200428 and radio bursts 221014 and 221021,which supply strong clues to constrain the trigger mechanism of FRBs or radio bursts.
基金supported by the National Natural Science Foundation of China(Nos.11273020,U1731111 and 11847048)the Sichuan Provincial Department of Science and Technology Project(No.2018JY0502)the Fundamental Research Funds of China West Normal University(No.20B009)。
文摘Pulsar timing is a classic technology of detecting irregularities in pulsar rotation.We carried out this method for 18 young radio pulsars,with long-term timing observations obtained between 2007 and 2015 using the Parkes 64-m radio telescope.As a result,30 glitches were identified,ranging from 0.75 × 10^(-9) to 8.6 × 10^(-6) in the relative glitch sizes Δv/v,where v=1/P is the pulse frequency.These glitches are composed of 26 new glitches and four published glitches with new exponential recoveries.All pulsars exhibit normal glitches,and six pulsars were observed to undergo a glitch event for the first time.We discuss the properties and implications for neutron-star physics of these glitches,and show that they are in agreement with previous work,except that the cumulative probability distributions of the mean waiting times for PSRs J0537-6910,J1341-6220 and J1740-3015 are not in consonance with the Poisson model.
基金supported in part by the National Natural Science Foundation of China(Grant Nos.11847048,11947128 and 11947018)the Fundamental Research Funds of China West Normal University(Grant Nos.20B009,17E093 and 18Q067)。
文摘In this paper,the Joule–Thomson expansion of the higher dimensional nonlinearly anti-de Sitter(Ad S)black hole with power Maxwell invariant source is investigated.The results show the Joule–Thomson coefficient has a zero point and a divergent point,which coincide with the inversion temperature Tiand the zero point of the Hawking temperature,respectively.The inversion temperature increases monotonously with inversion pressure.For the high-pressure region,the inversion temperature decreases with the dimensionality D and the nonlinearity parameter s,whereas it increases with the charge Q.However,Tifor the low-pressure region increase with D and s,while it decreases with Q.The ratioηBHbetween the minimum inversion temperature and the critical temperature does not depend on Q,it recovers the higher dimensional Reissner–N?rdstrom Ad S black hole case when s=1.However,for s>1,it becomes smaller and smaller as D increases and approaches a constant when D→∞.Finally,we found that an increase of mass M and s,or reducing the charge Q and D can enhance the isenthalpic curve,and the effect of s on the isenthalpic curve is much greater than other parameters.
