The detection of quasi-periodic oscillations(QPOs)in magnetar giant flares(GFs)has brought a new perspective to studies of the mechanism of magnetar bursts.Due to the scarcity of GFs,searching for QPOs in magnetar sho...The detection of quasi-periodic oscillations(QPOs)in magnetar giant flares(GFs)has brought a new perspective to studies of the mechanism of magnetar bursts.Due to the scarcity of GFs,searching for QPOs in magnetar short bursts is reasonable.Here we report the detection of a narrow QPO at approximately 110 Hz and a wide QPO at approximately 60 Hz in the short magnetar burst SGR 150228213,with a confidence level of 3.35σ.This burst was initially attributed to 4U 0142+61 by Fermi/GBM on location,but we have not detected such QPOs in other bursts from this magnetar.We also found that there was a repeating fast radio burst associated with SGR 150228213 on location.Finally,we discuss the possible origins of SGR 150228213.展开更多
We examine systematically the observed X-ray luminosity jumps(or flares) from quiescent states in millisecond binary pulsars(MSBPs) and high-mass X-ray binary pulsars(HMXBPs). We rely on the published X-ray light curv...We examine systematically the observed X-ray luminosity jumps(or flares) from quiescent states in millisecond binary pulsars(MSBPs) and high-mass X-ray binary pulsars(HMXBPs). We rely on the published X-ray light curves of seven pulsars: four HMXBPs, two MSBPs and the ultraluminous X-ray pulsar M82 X-2. We discuss the physics of their flaring activities or lack thereof, paying special attention to their emission properties when they are found on the propeller line, inside the Corbet gap or near the light-cylinder barrier. We provide guiding principles for future interpretations of faint X-ray observations, as well as a method of constraining the propeller lines and the dipolar surface magnetic fields of pulsars using a variety of quiescent states. In the process, we clarify some disturbing inaccuracies that have made their way into the published literature.展开更多
The anomalous X-ray pulsar 4U 0142＋61 has been studied with obser- vations from INTEGRAL. The hard X-ray spectrum in the range 18-500 keV for 4U 0142＋61 was derived using nearly nine years of INTEGRAL/IBIS data. We ...The anomalous X-ray pulsar 4U 0142＋61 has been studied with obser- vations from INTEGRAL. The hard X-ray spectrum in the range 18-500 keV for 4U 0142＋61 was derived using nearly nine years of INTEGRAL/IBIS data. We ob- tained the average hard X-ray spectrum of 4U 0142＋61 with all available data. The spectrum of 4U 0142＋61 can be fitted with a power law that includes an exponen- tial high energy cutoff. This average spectrum is well fitted by a power law with r ,~ 0.51 ± 0.11 plus a cutoff energy at 128.6 ± 17.2 keV. The hard X-ray flux of the source from 20-150 keV showed no significant variations （within 20%） from 2003- 2011. The spectral profiles have some variability over the nine years such that the photon index varies from 0.3-1.5 and the cutoff energies from 110-250 keV. The de- tection of the high energy cutoff around 130 keV shows some constraints on the radia- tion mechanisms of magnetars and possibly probes the differences between magnetar and accretion models for this special class of neutron stars. Future HXMTobservations could provide stronger constraints on the hard X-ray spectral properties of this source and other magnetar candidates.展开更多
A circumstellar corona is proposed to explain a strange quark-cluster star during an accretion phase, which could be essential for understanding the observa- tions of the puzzling symbiotic X-ray system 4U 1700＋24. T...A circumstellar corona is proposed to explain a strange quark-cluster star during an accretion phase, which could be essential for understanding the observa- tions of the puzzling symbiotic X-ray system 4U 1700＋24. The state of cold matter at supranuclear density is still an important matter of debate, and one of the con- sequences of a strange star acting as a pulsar is the self-bound phenomenon on the surface, which makes extremely low-mass compact objects unavoidable. In principle, both the redshifted O VIII Ly-c~ emission line and the change in the blackbody radi- ation area could naturally be understood if 4U 1700＋24 is a low-mass quark-cluster star which exhibits wind accretion.展开更多
We report an indication （3.22 or） of ≈ 1860 Hz quasi-periodic oscillations from a neutron star low-mass X-ray binary 4U 1636-536. If confirmed, this will be by far the highest frequency feature observed from an acc...We report an indication （3.22 or） of ≈ 1860 Hz quasi-periodic oscillations from a neutron star low-mass X-ray binary 4U 1636-536. If confirmed, this will be by far the highest frequency feature observed from an accreting neutron star system, and hence could be very useful in understanding such systems. This plausible timing feature was observed simultaneously with lower （≈ 585 Hz） and upper （≈ 904 Hz） kilohertz quasi-periodic oscillations. The two kilohertz quasi-periodic oscillation frequencies had a ratio of ≈ 1.5, and the frequency of the alleged ≈ 1860 Hz feature was close to the triple and the double values of these frequencies. This can be useful for constraining the models of all the three features. In particular, the ≈ 1860Hz feature could be （1） from a new and heretofore unknown class of quasi-periodic oscillations, or （2） the first observed overtone of lower or upper kilohertz quasi-periodic oscillations. Finally, we note that, although the relatively low significance of the ≈ 1860 Hz feature argues for caution, even a 3.22 σ feature at such a uniquely high frequency should be interesting enough to spur a systematic search in the archival data, as well as to scientifically motivate sufficiently large timing instruments for the next generation X-ray missions.展开更多
The X-ray variability in the soft X-ray spectral state of black hole binaries is primarily characterized by a power-law noise(PLN), which is thought to originate from the propagation of the modulation in the mass accr...The X-ray variability in the soft X-ray spectral state of black hole binaries is primarily characterized by a power-law noise(PLN), which is thought to originate from the propagation of the modulation in the mass accretion rate of a standard accretion disk flow. Such a PLN has also been revealed in the disk spectral component in the hard and the intermediate states in several black hole binaries. Here we present an investigation of the Rossi X-ray Timing Explorer(RXTE) observations of four black hole transients in which soft spectral states were observed twenty times or more. We show that in the soft spectral state, the PLN index varied in a large range between –1.64 and –0.62, and the fractional rms variability calculated in the 0.01 – 20 Hz frequency range reached as large as 7.67% and as low as 0.83%. Remarkably,we have found evidence of an inclination dependence of the maximal fractional rms variability, the averaged fractional rms variability and the fractional rms variability of the median in the sample based on current knowledge of inclination of black hole binaries. An inclination dependence has only been predicted in early magnetohydrodynamic simulations of isothermal disks limited to a high-frequency regime. In theory,the noise index is related to the physics of inward propagation of disk fluctuations, while the fractional rms amplitude reflects the intrinsic properties of the magnetohydrodynamic nature of the accretion flow.Our results therefore suggest that X-ray variability in the soft state can be used to put constraints on the properties of the accretion flow as well as the inclination of the accretion disk.展开更多
基金supported by the National Natural Science Foundation of China(grant Nos.12203013,12273005,and U1938201)China Manned Spaced Project(CMS-CSST-2021-B11)the Guangxi Science Foundation(grant Nos.AD22035171 and 2023GXNSFBA026030)。
文摘The detection of quasi-periodic oscillations(QPOs)in magnetar giant flares(GFs)has brought a new perspective to studies of the mechanism of magnetar bursts.Due to the scarcity of GFs,searching for QPOs in magnetar short bursts is reasonable.Here we report the detection of a narrow QPO at approximately 110 Hz and a wide QPO at approximately 60 Hz in the short magnetar burst SGR 150228213,with a confidence level of 3.35σ.This burst was initially attributed to 4U 0142+61 by Fermi/GBM on location,but we have not detected such QPOs in other bursts from this magnetar.We also found that there was a repeating fast radio burst associated with SGR 150228213 on location.Finally,we discuss the possible origins of SGR 150228213.
基金supported by NASA grant NNX14-AF77Gsupported by a NASA ADAP grant
文摘We examine systematically the observed X-ray luminosity jumps(or flares) from quiescent states in millisecond binary pulsars(MSBPs) and high-mass X-ray binary pulsars(HMXBPs). We rely on the published X-ray light curves of seven pulsars: four HMXBPs, two MSBPs and the ultraluminous X-ray pulsar M82 X-2. We discuss the physics of their flaring activities or lack thereof, paying special attention to their emission properties when they are found on the propeller line, inside the Corbet gap or near the light-cylinder barrier. We provide guiding principles for future interpretations of faint X-ray observations, as well as a method of constraining the propeller lines and the dipolar surface magnetic fields of pulsars using a variety of quiescent states. In the process, we clarify some disturbing inaccuracies that have made their way into the published literature.
基金Supported by the National Natural Science Foundation of China
文摘The anomalous X-ray pulsar 4U 0142＋61 has been studied with obser- vations from INTEGRAL. The hard X-ray spectrum in the range 18-500 keV for 4U 0142＋61 was derived using nearly nine years of INTEGRAL/IBIS data. We ob- tained the average hard X-ray spectrum of 4U 0142＋61 with all available data. The spectrum of 4U 0142＋61 can be fitted with a power law that includes an exponen- tial high energy cutoff. This average spectrum is well fitted by a power law with r ,~ 0.51 ± 0.11 plus a cutoff energy at 128.6 ± 17.2 keV. The hard X-ray flux of the source from 20-150 keV showed no significant variations （within 20%） from 2003- 2011. The spectral profiles have some variability over the nine years such that the photon index varies from 0.3-1.5 and the cutoff energies from 110-250 keV. The de- tection of the high energy cutoff around 130 keV shows some constraints on the radia- tion mechanisms of magnetars and possibly probes the differences between magnetar and accretion models for this special class of neutron stars. Future HXMTobservations could provide stronger constraints on the hard X-ray spectral properties of this source and other magnetar candidates.
基金Supported by the National Natural Science Foundation of China
文摘A circumstellar corona is proposed to explain a strange quark-cluster star during an accretion phase, which could be essential for understanding the observa- tions of the puzzling symbiotic X-ray system 4U 1700＋24. The state of cold matter at supranuclear density is still an important matter of debate, and one of the con- sequences of a strange star acting as a pulsar is the self-bound phenomenon on the surface, which makes extremely low-mass compact objects unavoidable. In principle, both the redshifted O VIII Ly-c~ emission line and the change in the blackbody radi- ation area could naturally be understood if 4U 1700＋24 is a low-mass quark-cluster star which exhibits wind accretion.
文摘We report an indication （3.22 or） of ≈ 1860 Hz quasi-periodic oscillations from a neutron star low-mass X-ray binary 4U 1636-536. If confirmed, this will be by far the highest frequency feature observed from an accreting neutron star system, and hence could be very useful in understanding such systems. This plausible timing feature was observed simultaneously with lower （≈ 585 Hz） and upper （≈ 904 Hz） kilohertz quasi-periodic oscillations. The two kilohertz quasi-periodic oscillation frequencies had a ratio of ≈ 1.5, and the frequency of the alleged ≈ 1860 Hz feature was close to the triple and the double values of these frequencies. This can be useful for constraining the models of all the three features. In particular, the ≈ 1860Hz feature could be （1） from a new and heretofore unknown class of quasi-periodic oscillations, or （2） the first observed overtone of lower or upper kilohertz quasi-periodic oscillations. Finally, we note that, although the relatively low significance of the ≈ 1860 Hz feature argues for caution, even a 3.22 σ feature at such a uniquely high frequency should be interesting enough to spur a systematic search in the archival data, as well as to scientifically motivate sufficiently large timing instruments for the next generation X-ray missions.
基金supported in part by the National Program on Key Research and Development Project(Grant No.2016YFA0400804)the National Natural Science Foundation of China(Grant Nos.11333005 and U1838203)the support by the FAST Scholar fellowship,which is supported by special funding for advanced users,budgeted and administrated by Center for Astronomical Mega-Science,Chinese Academy of Sciences(CAMS)。
文摘The X-ray variability in the soft X-ray spectral state of black hole binaries is primarily characterized by a power-law noise(PLN), which is thought to originate from the propagation of the modulation in the mass accretion rate of a standard accretion disk flow. Such a PLN has also been revealed in the disk spectral component in the hard and the intermediate states in several black hole binaries. Here we present an investigation of the Rossi X-ray Timing Explorer(RXTE) observations of four black hole transients in which soft spectral states were observed twenty times or more. We show that in the soft spectral state, the PLN index varied in a large range between –1.64 and –0.62, and the fractional rms variability calculated in the 0.01 – 20 Hz frequency range reached as large as 7.67% and as low as 0.83%. Remarkably,we have found evidence of an inclination dependence of the maximal fractional rms variability, the averaged fractional rms variability and the fractional rms variability of the median in the sample based on current knowledge of inclination of black hole binaries. An inclination dependence has only been predicted in early magnetohydrodynamic simulations of isothermal disks limited to a high-frequency regime. In theory,the noise index is related to the physics of inward propagation of disk fluctuations, while the fractional rms amplitude reflects the intrinsic properties of the magnetohydrodynamic nature of the accretion flow.Our results therefore suggest that X-ray variability in the soft state can be used to put constraints on the properties of the accretion flow as well as the inclination of the accretion disk.
