A pulsating ultraluminous X-ray source(PULX)is a new kind of pulsar(PSR)whose characteristics are different from all known neutron stars.The magnetic field of PULX is suspected to be the main reason to support its sup...A pulsating ultraluminous X-ray source(PULX)is a new kind of pulsar(PSR)whose characteristics are different from all known neutron stars.The magnetic field of PULX is suspected to be the main reason to support its supper Eddington luminosity of PULX.NGC 7793 P13,which is the second confirmed PULX,can be easily studied due to its nearby position and isolation from other sources in its host galaxy.In this paper,we calculate its magnetic field to be∼1.0×10^(12) G based on the continued observations from 2016 to 2020.The magnetic field evolution of NGC 7793 P13 is analyzed,which shows that the source has spent about 10^(4) yr for the field decaying from the simulated initial strength 4.0×10^(14) G to the present value.In case of an assumed constant accretion and the limitation of the companion mass,it will be a recycled PSR whose magnetic field is ∼10^(9) G and spin period is a few hundred milliseconds.We estimate the field strength of the other confirmed PULXs and find main range is 10^(13)-10^(14) G.Their positions of the magnetic field and spin period are around or below the magnetars.This is because these PULXs are in the binary systems and are with the spin-up rate that are 2-3 orders higher than the normal binary pulsars.We suggest that PULXs are the accreting magnetars whose multi-pole strong magnetic field can support the supper Eddington luminosity.They would be helpful for studying the evolution of the magnetars,the formation of the binary PSRs above the Eddington spin-up line,and the millisecond PSRs with the magnetic field stronger than ∼10^(9) G.展开更多
Data from a recently discovered long Gamma Ray Burst (GRB 090102) by NASA’s Swift satellite revealed that such GRBs may not be fireballs as usually presumed, but instead they are powered and collimated by organized s...Data from a recently discovered long Gamma Ray Burst (GRB 090102) by NASA’s Swift satellite revealed that such GRBs may not be fireballs as usually presumed, but instead they are powered and collimated by organized strong magnetic fields (≧ 1015 G) generated by the compact object, a neutron star (NS) created at the core of the associated supernova explosion (SNeII). A mechanism for the generation of such strong surface magnetic fields where power NSs result from the deaths of massive progenitor stars is described based on a non-conventional model for pulsar magnetic fields, namely, spinning polarization charge that I recently developed in [1]. I show that this could give rise to scenarios involving long GRB events as the one captured by the Swift satellite during GRB 090102 in January 2, 2009. The model predicts that the magnetic moment of a NS has a dynamical feature which makes it different from that of a simple pulsar. I show this could have serious consequences on the statistics of observing long GRBs and also help explain such scenarios as the steep decline in the photon count-rate and the subsequent shutoff in the Swift/XRT X-ray data from GRB 070110.展开更多
In multiple experiments plates of melanoma cells separated by either 3 m or 1.7 km were placed in the centers of toroids. A specific protocol of changing, angular velocity, pulsed magnetic fields that has been shown t...In multiple experiments plates of melanoma cells separated by either 3 m or 1.7 km were placed in the centers of toroids. A specific protocol of changing, angular velocity, pulsed magnetic fields that has been shown to produce excess correlation in photon durations and shift in proton concentrations (pH) in spring water were generated around both plates of cells. Serial injections of 50 μL of standard concentrations of hydrogen peroxide into the “local” plates of cells during the 12 min of field activation produced conspicuous cell death (reduction of viable cells by about 50%) with comparable diminishments of cell numbers in the non-local plates of cells within 24 hr but only if both loci separated by either 3 m or 1.7 km had shared the “excess correlation” magnetic field sequence. The non-local effect did not occur if the magnetic fields had not been present. Higher or lower concentrations of peroxide or concentrations that eliminated all of the cells or very few cells in the local dishes were associated with no significant diminishment of non-local cell growth. The data indicate that there must be a critical number of cells remaining viable following the local chemical reaction for the excess correlation to be manifested in the non-local cells. We suggest that this specific spatial-temporal pattern of fields generated within the paired toroidal geometries promotes transposition of virtual chemical reactions as an information field. Calculations of the energy available per cell and per volume of the quantity of reactants injected into the local space from the intensity of the changing velocity toroidal magnetic field support previous measurements and derivations that the units of information transposition may involve discrete quantities that represent equivalents of photons, electrons and protons.展开更多
Magnetic fields are observed everywhere in the universe.In this review,we concentrate on the observational aspects of the magnetic fields of Galactic and extragalactic objects.Readers can follow the milesones in the o...Magnetic fields are observed everywhere in the universe.In this review,we concentrate on the observational aspects of the magnetic fields of Galactic and extragalactic objects.Readers can follow the milesones in the observations of cosmic magnetic fields obtained from the most important tracers of magnetic fields,namely,the star-light polarization,the Zeeman effect,the rotation measures9RMs, hereafter) of extragalactic radio sources,the pulsar RMs, radio polarization observations as well as the newly implemented sub-mm and mm polarization capabilities.The magnetic field of the Galaxy was first discovered in 1949 by optical polarization observations.The local magnetic fields within one or two kpc have been well delineated by starlight polarization data.The polarization observations of diffuse Galactic radio background emission in 1962 confirmed unequivocally the existence of a Galactic magnetic field.The bulk of the present information about the magnetic fields in the Galaxy comes from analysis of rotation measures of extragalactic radio sources and pulsars,which can be used to construct the 3-D magnetic field structure in the Galactic halo and Galactic disk.Radio synchrotron spurs in the Galactic center show a poloidal field,and the polarization mapping of dust emission and Zeeman observation in the central molecular zone reveal a toroidal magnetic field parallel to the Galactic plane.For nearby galaxies,both optical polarization and multifrequency radio polarization data clearly show the large-scale magnetic field following the spiral arms or dust lanes.For more distant objects,radio polarization is the only approach available to show the magnetic fields in the jets or lobes of radio galaxies or quasars.Clusters of galaxies also contain widely distributed magnetic fields,which are reflected by radio halos or the RM distribution of background objects.The intergalactic space could have been magnetized by outflows or galactic superwinds even in the early universe.The Zeeman effect and polarization of sub-mm and mm emission can be used for the study of magnetic fields in some Galactic molecular clouds but it is observed only at high intensity.Bot approaches together can clearly show the role that magnetic fields play in star formation and cloud structure,which in principle would be analogous to galaxy formation from protogalactic clouds.The origin of the cosmic magnetic fields is an active field of research.A primordial magnetic field has not been as yet directly detected,but its existence must be considered to give the seed field necessary for many amplification processes that have been developed.Possibly,the magnetic fields were generated in protogalactic plasma clouds by the dynamo process,and maintained again by the dynamo after galaxies were formed.展开更多
Spring water but not double-distilled water was exposed, in darkness, to a temporally patterned weak magnetic field that has been shown to affect planarian behavior and slow the rate of cancer cell proliferation. Expo...Spring water but not double-distilled water was exposed, in darkness, to a temporally patterned weak magnetic field that has been shown to affect planarian behavior and slow the rate of cancer cell proliferation. Exposure to the magnetic field caused a reliable shift in the peak (longer) wave-length of ~10 nm for fluorescence emissions and a ~20% increase (~100 counts) in fluorescence intensity. Spectral analyses verified a shift of 5 and 10 nm, equivalent to ~1.5 × 10-20 J “periodicity” across the measured wavelengths, which could reflect a change in the an intrinsic energy as predicted by Del Giudice and Preparata and could correspond to two lengths of O-H bonds. Wrapping the water sample containers during exposure with copper foil, aluminum foil, or plastic altered these fluorescent profiles. The most conspicuous effect was the elimination of a ~280 nm peak in the UV-VIS emission spectra only for samples wrapped with copper foil but not aluminum or plastic. These results suggest that weak magnetic fields produce alterations in the water-ionic complexes sufficient to be reliably measured by spectrophotometry. Because the effect was most pronounced when the spring water was exposed in darkness and was not disturbed the role of thixotropic phenomena and Del Giudice entrapment of magnetic fields within coherent domains of Pollack virtual exclusion zones (EZ) may have set the conditions for subsequent release of the energy as photons.展开更多
Pulsars play a crucial astrophy sical role as highly energetic compact radio, X-ray and gammaray sources. Our previous works show that radio pulsars identified as pulsing gamma-ray sources by the Large Area Telescope(...Pulsars play a crucial astrophy sical role as highly energetic compact radio, X-ray and gammaray sources. Our previous works show that radio pulsars identified as pulsing gamma-ray sources by the Large Area Telescope(LAT) on board the Fermi Gamma-Ray Space Telescope have high values of magnetic field near the light cylinder, two-three orders of magnitude stronger compared with the magnetic fields of radio pulsars: log B_(lc)(G) are 3.60-3.95 and 1.75 correspondingly. Moreover,their losses of rotational energy are also three orders higher than the corresponding values for the main group of radio pulsars on average: log E(erg s^(-1)) = 35.37-35.53 and 32.64. The correlation between gammaray luminosities and radio luminosities is found. It allows us to select those objects from all sets of known radio pulsars that can be detected as gamma-ray pulsars with high probability. We provide a list of such radio pulsars and propose to search for gamma emission from these objects. On the other hand,the known catalog of gamma-ray pulsars contains some sources which are not currently identified as radio pulsars. Some of them have large values of gamma-ray luminosities and according to the obtained correlation, we can expect marked radio emission from these objects. We give the list of such pulsars and expected flux densities to search for radiation at frequencies 1400 and 111 MHz.展开更多
Fast radio bursts(FRBs) are a type of newly-discovered transient astronomical phenomenon.They have short durations, high dispersion measures and a high event rate. However, due to unknown distances and undetected elec...Fast radio bursts(FRBs) are a type of newly-discovered transient astronomical phenomenon.They have short durations, high dispersion measures and a high event rate. However, due to unknown distances and undetected electromagnetic counterparts at other wavebands, it is difficult to further investigate FRBs. Here we propose a method to study their environmental magnetic field using an indirect method.Starting with dispersion measures and rotation measures(RMs), we try to obtain the parallel magnetic field component ■ which is the average value along the line of sight in the host galaxy. Because both RMs and redshifts are now unavailable, we demonstrate the dependence of ■ on these two separate quantities.This result, if the RM and redshift of an FRB are measured, would be expected to provide a clue towards understanding an environmental magnetic field of an FRB.展开更多
Disks originating from supernova fallback have been suggested to surround young neutron stars. Interaction between the disk and the magnetic field of the neutron star may considerably influence the evolution of the st...Disks originating from supernova fallback have been suggested to surround young neutron stars. Interaction between the disk and the magnetic field of the neutron star may considerably influence the evolution of the star through the so called propeller effect. There are many controversies about the efficiency of the propeller mechanism proposed in the literature. We investigate the fallback diskinvolved spin-down of young pulsars. By comparing the simulated and measured results of pulsar evolution, we present some possible constraints on the propeller torques exerted by the disks on neutron stars.展开更多
According to two estimated relations between the initial period andthe dynamo-generated magnetic dipole field of pulsars, we calculate the statisticaldistributions of pulsar initial periods. It is found that proto-pul...According to two estimated relations between the initial period andthe dynamo-generated magnetic dipole field of pulsars, we calculate the statisticaldistributions of pulsar initial periods. It is found that proto-pulsars are very likelyto have rotation periods between 20 ms and 30 ms, and that most of the pulsarsrotate initially at a period < 60 ms. Our result supports the asymmetric neutrinoemission model for pulsar kick.展开更多
We analyze sunspot rotation and magnetic transients in NOAA AR 11429 during two X-class(X5.4 and X1.3)flares using data from the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory.A large leading...We analyze sunspot rotation and magnetic transients in NOAA AR 11429 during two X-class(X5.4 and X1.3)flares using data from the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory.A large leading sunspot with positive magnetic polarity rotated counterclockwise.As expected,the rotation was significantly affected by the two flares.Magnetic transients induced by the flares were clearly evident in the sunspots with negative polarity.They were moving across the sunspots with speed of order 3-7 km s^(-1).Furthermore,the trend of magnetic flux evolution in these sunspots exhibited changes associated with the flares.These results may shed light on understanding the evolution of sunspots.展开更多
The inner vacuum gap model has become the foundation stone of most theories on pulsar radio emission. The fundamental picture of this model is the sparking, which was conjectured to be induced by magnetic absorption o...The inner vacuum gap model has become the foundation stone of most theories on pulsar radio emission. The fundamental picture of this model is the sparking, which was conjectured to be induced by magnetic absorption of background gamma photons. However, a question is, can the sparking be triggered in the millisecond pulsars (MSPs) with magnetic fields (B) only about 10s G? We investigate this problem by including the pair production above the inner gap. Under the assumption that the magnetic field is dipolar, our results show the background gamma-ray emission can not be the key factor that triggers the sparking, at least not in MSPs with B ~ 108 G, if the temperature in the polar cap region is only so high as is observed (< 4 × 106 K). Some other mechanisms are required.展开更多
The Five-hundred-meter Aperture Spherical radio Telescope(FAST)is the most sensitive radio telescope for pulsar observations.We make polarimetric measurements of a large number of faint and distant pulsars using the F...The Five-hundred-meter Aperture Spherical radio Telescope(FAST)is the most sensitive radio telescope for pulsar observations.We make polarimetric measurements of a large number of faint and distant pulsars using the FAST.We present the new measurements of Faraday rotation for 134 faint pulsars in the Galactic halo.Significant improvements are also made for some basic pulsar parameters for 15 of them.We analyse the newly determined rotation measures(RMs)for the Galactic magnetic fields by using these 134 halo pulsars,together with previously available RMs for pulsars and extragalactic radio sources and also the newly determined RMs for another 311 faint pulsars which are either newly discovered in the project of the Galactic Plane Pulsar Snapshot(GPPS)survey or previously known pulsars without RMs.The RM tomographic analysis in the first Galactic quadrant gives roughly the same field strength of around 2μG for the large-scale toroidal halo magnetic fields.The scale height of the halo magnetic fields is found to be at least 2.7±0.3 kpc.The RM differentiation of a large number of pulsars in the Galactic disk in the Galactic longitude range of 26°<l<90°gives evidence for the clockwise magnetic fields(viewed from the north Galactic pole)in two interarm regions inside the Scutum arm and between the Scutum and Sagittarius arm,and the clockwise fields in the Local-Perseus interarm region and field reversals in the Perseus arm and beyond.展开更多
Average pulse profiles of pulsar signals are analyzed using the bispectrum tech-nique. The result shows that there are nonlinear phase couplings between the two frequency axes of the bispectrum charts, which indicate ...Average pulse profiles of pulsar signals are analyzed using the bispectrum tech-nique. The result shows that there are nonlinear phase couplings between the two frequency axes of the bispectrum charts, which indicate nonlinear factors in the generation and prop-agation of pulsar signals. Bispectra can be used as feature vectors of pulsar signals because of their being translation invariant. A one-dimension selected line spectrum algorithm for ex-tracting pulsar signal characteristic is proposed. Compared with selected bispectra, the pro-posed selected line spectra have the maximum interclass separability measurements from the point of view of the whole one-dimension feature vector. Recognition experiments on several pulsar signals received at several frequency bands are carried out. The result shows that the selected line spectrum algorithm is suitable for extracting pulsar signal characteristics and has a good classification performance.展开更多
We employ the supernova fallback disk model to simulate the spin evolution of isolated young neutron stars(NSs). We consider the submergence of the NS magnetic fields during the supercritical accretion stage and its s...We employ the supernova fallback disk model to simulate the spin evolution of isolated young neutron stars(NSs). We consider the submergence of the NS magnetic fields during the supercritical accretion stage and its succeeding reemergence. It is shown that the evolution of the spin periods and the magnetic fields in this model is able to account for the relatively weak magnetic fields of central compact objects and the measured braking indices of young pulsars. For a range of initial parameters, evolutionary links can be established among various kinds of NS sub-populations including magnetars, central compact objects and young pulsars. Thus, the diversity of young NSs could be unified in the framework of the supernova fallback accretion model.展开更多
We model the evolution of the spin frequency's second derivative ν¨ and the braking index n of radio pulsars with simulations within the phenomenological model of their surface magnetic field evolution, whic...We model the evolution of the spin frequency's second derivative ν¨ and the braking index n of radio pulsars with simulations within the phenomenological model of their surface magnetic field evolution, which contains a long-term power-law decay modulated by short-term oscillations. For the pulsar PSR B0329+54, a model with three oscillation components can reproduce its ν¨ variation. We show that the "averaged" n is different from the instantaneous n, and its oscillation magnitude decreases abruptly as the time span increases, due to the "averaging" effect. The simulated timing residuals agree with the main features of the reported data. Our model predicts that the averaged ν¨ of PSR B0329+54 will start to decrease rapidly with newer data beyond those used in Hobbs et al. We further perform Monte Carlo simulations for the distribution of the reported data in |ν¨| and |n| versus characteristic age τcdiagrams.It is found that the magnetic field oscillation model with decay index α = 0 can reproduce the distributions quite well. Compared with magnetic field decay due to the ambipolar diffusion(α = 0.5) and the Hall cascade(α = 1.0), the model with no long term decay(α = 0) is clearly preferred for old pulsars by the p-values of the two-dimensional Kolmogorov-Smirnov test.展开更多
Since there is a large population of massive O/B stars and putative neutron stars(NSs) located in the vicinity of the Galactic Center(GC),intermediate-mass X-ray binaries(IMXBs) constituted by an NS and a B-type star ...Since there is a large population of massive O/B stars and putative neutron stars(NSs) located in the vicinity of the Galactic Center(GC),intermediate-mass X-ray binaries(IMXBs) constituted by an NS and a B-type star probably exist there.We investigate the evolutions of accreting NSs in IMXBs(similar to M82 X-2) with a ~ 5.2 M⊙companion and orbital period■ 2.53 d.By adopting a mildly super-Eddington rate M= 6 × 10^(-8) M⊙yr^(-1) for the early Case B Roche-lobe overflow(RLOF)accretion,we find that only in accreting NSs with quite elastic crusts(slippage factor s = 0.05) can the toroidal magnetic fields be amplified within 1 Myr,which is assumed to be the longest duration of the RLOF.These IMXBs will evolve into NS+white dwarf(WD) binaries if they are dynamically stable.However,before the formation of NS+WD binaries,the high stellar density in the GC will probably lead to frequent encounters between the NS+ evolved star binaries(in post-early Case B mass transfer phase)and NSs or exchange encounters with other stars,which may produce single NSs.These NSs will evolve into magnetars when the amplified poloidal magnetic fields diffuse out to the NS surfaces.Consequently,our results provide a possible explanation for the origin of the GC magnetar SGR 1745–2900.Moreover,the accreting NSs with s > 0.05 will evolve into millisecond pulsars(MSPs).Therefore,our model reveals that the GC magnetars and MSPs could both originate from a special kind of IMXB.展开更多
Fast radio bursts (FRBs) at cosmological distances still hold concealed physical origins. Previously Liu (2018) proposes a scenario that the collision between a neutron star (NS) and a white dwarf (WD) can be one of t...Fast radio bursts (FRBs) at cosmological distances still hold concealed physical origins. Previously Liu (2018) proposes a scenario that the collision between a neutron star (NS) and a white dwarf (WD) can be one of the progenitors of non-repeating FRBs and notices that the repeating FRBs can also be explained if a magnetar formed after such NS-WD merger. In this paper, we investigate this channel of magnetar formation in more detail. We propose that the NS-WD post-merger, after cooling and angular momentum redistribution, may collapse to either a black hole or a new NS or even remains as a hybrid WDNS, depending on the total mass of the NS and WD. In particular, the newly formed NS can be a magnetar if the core of the WD collapsed into the NS while large quantities of degenerate electrons of the WD compressed to the outer layers of the new NS. A strong magnetic field can be formed by the electrons and positive charges with different angular velocities induced by the differential rotation of the newborn magnetar. Such a magnetar can power the repeating FRBs by the magnetic reconnections due to the crustal movements or starquakes.展开更多
基金supported by the National Natural Science Foundation of China(12130342,12273030 and U1938107)。
文摘A pulsating ultraluminous X-ray source(PULX)is a new kind of pulsar(PSR)whose characteristics are different from all known neutron stars.The magnetic field of PULX is suspected to be the main reason to support its supper Eddington luminosity of PULX.NGC 7793 P13,which is the second confirmed PULX,can be easily studied due to its nearby position and isolation from other sources in its host galaxy.In this paper,we calculate its magnetic field to be∼1.0×10^(12) G based on the continued observations from 2016 to 2020.The magnetic field evolution of NGC 7793 P13 is analyzed,which shows that the source has spent about 10^(4) yr for the field decaying from the simulated initial strength 4.0×10^(14) G to the present value.In case of an assumed constant accretion and the limitation of the companion mass,it will be a recycled PSR whose magnetic field is ∼10^(9) G and spin period is a few hundred milliseconds.We estimate the field strength of the other confirmed PULXs and find main range is 10^(13)-10^(14) G.Their positions of the magnetic field and spin period are around or below the magnetars.This is because these PULXs are in the binary systems and are with the spin-up rate that are 2-3 orders higher than the normal binary pulsars.We suggest that PULXs are the accreting magnetars whose multi-pole strong magnetic field can support the supper Eddington luminosity.They would be helpful for studying the evolution of the magnetars,the formation of the binary PSRs above the Eddington spin-up line,and the millisecond PSRs with the magnetic field stronger than ∼10^(9) G.
文摘Data from a recently discovered long Gamma Ray Burst (GRB 090102) by NASA’s Swift satellite revealed that such GRBs may not be fireballs as usually presumed, but instead they are powered and collimated by organized strong magnetic fields (≧ 1015 G) generated by the compact object, a neutron star (NS) created at the core of the associated supernova explosion (SNeII). A mechanism for the generation of such strong surface magnetic fields where power NSs result from the deaths of massive progenitor stars is described based on a non-conventional model for pulsar magnetic fields, namely, spinning polarization charge that I recently developed in [1]. I show that this could give rise to scenarios involving long GRB events as the one captured by the Swift satellite during GRB 090102 in January 2, 2009. The model predicts that the magnetic moment of a NS has a dynamical feature which makes it different from that of a simple pulsar. I show this could have serious consequences on the statistics of observing long GRBs and also help explain such scenarios as the steep decline in the photon count-rate and the subsequent shutoff in the Swift/XRT X-ray data from GRB 070110.
文摘In multiple experiments plates of melanoma cells separated by either 3 m or 1.7 km were placed in the centers of toroids. A specific protocol of changing, angular velocity, pulsed magnetic fields that has been shown to produce excess correlation in photon durations and shift in proton concentrations (pH) in spring water were generated around both plates of cells. Serial injections of 50 μL of standard concentrations of hydrogen peroxide into the “local” plates of cells during the 12 min of field activation produced conspicuous cell death (reduction of viable cells by about 50%) with comparable diminishments of cell numbers in the non-local plates of cells within 24 hr but only if both loci separated by either 3 m or 1.7 km had shared the “excess correlation” magnetic field sequence. The non-local effect did not occur if the magnetic fields had not been present. Higher or lower concentrations of peroxide or concentrations that eliminated all of the cells or very few cells in the local dishes were associated with no significant diminishment of non-local cell growth. The data indicate that there must be a critical number of cells remaining viable following the local chemical reaction for the excess correlation to be manifested in the non-local cells. We suggest that this specific spatial-temporal pattern of fields generated within the paired toroidal geometries promotes transposition of virtual chemical reactions as an information field. Calculations of the energy available per cell and per volume of the quantity of reactants injected into the local space from the intensity of the changing velocity toroidal magnetic field support previous measurements and derivations that the units of information transposition may involve discrete quantities that represent equivalents of photons, electrons and protons.
文摘Magnetic fields are observed everywhere in the universe.In this review,we concentrate on the observational aspects of the magnetic fields of Galactic and extragalactic objects.Readers can follow the milesones in the observations of cosmic magnetic fields obtained from the most important tracers of magnetic fields,namely,the star-light polarization,the Zeeman effect,the rotation measures9RMs, hereafter) of extragalactic radio sources,the pulsar RMs, radio polarization observations as well as the newly implemented sub-mm and mm polarization capabilities.The magnetic field of the Galaxy was first discovered in 1949 by optical polarization observations.The local magnetic fields within one or two kpc have been well delineated by starlight polarization data.The polarization observations of diffuse Galactic radio background emission in 1962 confirmed unequivocally the existence of a Galactic magnetic field.The bulk of the present information about the magnetic fields in the Galaxy comes from analysis of rotation measures of extragalactic radio sources and pulsars,which can be used to construct the 3-D magnetic field structure in the Galactic halo and Galactic disk.Radio synchrotron spurs in the Galactic center show a poloidal field,and the polarization mapping of dust emission and Zeeman observation in the central molecular zone reveal a toroidal magnetic field parallel to the Galactic plane.For nearby galaxies,both optical polarization and multifrequency radio polarization data clearly show the large-scale magnetic field following the spiral arms or dust lanes.For more distant objects,radio polarization is the only approach available to show the magnetic fields in the jets or lobes of radio galaxies or quasars.Clusters of galaxies also contain widely distributed magnetic fields,which are reflected by radio halos or the RM distribution of background objects.The intergalactic space could have been magnetized by outflows or galactic superwinds even in the early universe.The Zeeman effect and polarization of sub-mm and mm emission can be used for the study of magnetic fields in some Galactic molecular clouds but it is observed only at high intensity.Bot approaches together can clearly show the role that magnetic fields play in star formation and cloud structure,which in principle would be analogous to galaxy formation from protogalactic clouds.The origin of the cosmic magnetic fields is an active field of research.A primordial magnetic field has not been as yet directly detected,but its existence must be considered to give the seed field necessary for many amplification processes that have been developed.Possibly,the magnetic fields were generated in protogalactic plasma clouds by the dynamo process,and maintained again by the dynamo after galaxies were formed.
文摘Spring water but not double-distilled water was exposed, in darkness, to a temporally patterned weak magnetic field that has been shown to affect planarian behavior and slow the rate of cancer cell proliferation. Exposure to the magnetic field caused a reliable shift in the peak (longer) wave-length of ~10 nm for fluorescence emissions and a ~20% increase (~100 counts) in fluorescence intensity. Spectral analyses verified a shift of 5 and 10 nm, equivalent to ~1.5 × 10-20 J “periodicity” across the measured wavelengths, which could reflect a change in the an intrinsic energy as predicted by Del Giudice and Preparata and could correspond to two lengths of O-H bonds. Wrapping the water sample containers during exposure with copper foil, aluminum foil, or plastic altered these fluorescent profiles. The most conspicuous effect was the elimination of a ~280 nm peak in the UV-VIS emission spectra only for samples wrapped with copper foil but not aluminum or plastic. These results suggest that weak magnetic fields produce alterations in the water-ionic complexes sufficient to be reliably measured by spectrophotometry. Because the effect was most pronounced when the spring water was exposed in darkness and was not disturbed the role of thixotropic phenomena and Del Giudice entrapment of magnetic fields within coherent domains of Pollack virtual exclusion zones (EZ) may have set the conditions for subsequent release of the energy as photons.
基金financial support of Basic Research Program of the Presidium of the Russian Academy of Sciences"Transitional and Explosive Processes in Astrophysics(P-41)"Russian Foundation for Basic Research(grant 16–02–00954)
文摘Pulsars play a crucial astrophy sical role as highly energetic compact radio, X-ray and gammaray sources. Our previous works show that radio pulsars identified as pulsing gamma-ray sources by the Large Area Telescope(LAT) on board the Fermi Gamma-Ray Space Telescope have high values of magnetic field near the light cylinder, two-three orders of magnitude stronger compared with the magnetic fields of radio pulsars: log B_(lc)(G) are 3.60-3.95 and 1.75 correspondingly. Moreover,their losses of rotational energy are also three orders higher than the corresponding values for the main group of radio pulsars on average: log E(erg s^(-1)) = 35.37-35.53 and 32.64. The correlation between gammaray luminosities and radio luminosities is found. It allows us to select those objects from all sets of known radio pulsars that can be detected as gamma-ray pulsars with high probability. We provide a list of such radio pulsars and propose to search for gamma emission from these objects. On the other hand,the known catalog of gamma-ray pulsars contains some sources which are not currently identified as radio pulsars. Some of them have large values of gamma-ray luminosities and according to the obtained correlation, we can expect marked radio emission from these objects. We give the list of such pulsars and expected flux densities to search for radiation at frequencies 1400 and 111 MHz.
基金supported by the National Basic Research Program ("973" Program) of China (Grant No. 2014CB845800)the National Natural Science Foundation of China (Grant No. 11033002)
文摘Fast radio bursts(FRBs) are a type of newly-discovered transient astronomical phenomenon.They have short durations, high dispersion measures and a high event rate. However, due to unknown distances and undetected electromagnetic counterparts at other wavebands, it is difficult to further investigate FRBs. Here we propose a method to study their environmental magnetic field using an indirect method.Starting with dispersion measures and rotation measures(RMs), we try to obtain the parallel magnetic field component ■ which is the average value along the line of sight in the host galaxy. Because both RMs and redshifts are now unavailable, we demonstrate the dependence of ■ on these two separate quantities.This result, if the RM and redshift of an FRB are measured, would be expected to provide a clue towards understanding an environmental magnetic field of an FRB.
基金Supported by the National Natural Science Foundation of China.
文摘Disks originating from supernova fallback have been suggested to surround young neutron stars. Interaction between the disk and the magnetic field of the neutron star may considerably influence the evolution of the star through the so called propeller effect. There are many controversies about the efficiency of the propeller mechanism proposed in the literature. We investigate the fallback diskinvolved spin-down of young pulsars. By comparing the simulated and measured results of pulsar evolution, we present some possible constraints on the propeller torques exerted by the disks on neutron stars.
基金This work is supported by National Nature Sciences Foundation ofChina (10173002)the Special Funds for Major State Basic Research Projects of China (G2000077602)RXX wishes to sincerely acknowledge Mrs. S. Z. Peng for her help in preparing pulsar dat
文摘According to two estimated relations between the initial period andthe dynamo-generated magnetic dipole field of pulsars, we calculate the statisticaldistributions of pulsar initial periods. It is found that proto-pulsars are very likelyto have rotation periods between 20 ms and 30 ms, and that most of the pulsarsrotate initially at a period < 60 ms. Our result supports the asymmetric neutrinoemission model for pulsar kick.
基金supported by the National Natural Science Foundation of China (41231068, 41374187, 41531073 and 41674147)
文摘We analyze sunspot rotation and magnetic transients in NOAA AR 11429 during two X-class(X5.4 and X1.3)flares using data from the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory.A large leading sunspot with positive magnetic polarity rotated counterclockwise.As expected,the rotation was significantly affected by the two flares.Magnetic transients induced by the flares were clearly evident in the sunspots with negative polarity.They were moving across the sunspots with speed of order 3-7 km s^(-1).Furthermore,the trend of magnetic flux evolution in these sunspots exhibited changes associated with the flares.These results may shed light on understanding the evolution of sunspots.
基金Supported by the National Natural Science Foundation of China
文摘The inner vacuum gap model has become the foundation stone of most theories on pulsar radio emission. The fundamental picture of this model is the sparking, which was conjectured to be induced by magnetic absorption of background gamma photons. However, a question is, can the sparking be triggered in the millisecond pulsars (MSPs) with magnetic fields (B) only about 10s G? We investigate this problem by including the pair production above the inner gap. Under the assumption that the magnetic field is dipolar, our results show the background gamma-ray emission can not be the key factor that triggers the sparking, at least not in MSPs with B ~ 108 G, if the temperature in the polar cap region is only so high as is observed (< 4 × 106 K). Some other mechanisms are required.
基金supported by the National Natural Science Foundation of China(Grant Nos.11988101,11833009,and U2031115)the Key Research Program of the Chinese Academy of Sciences(Grant No.QYZDJSSW-SLH021)+2 种基金the National SKA Program of China(Grant No.2022SKA0120103)supported by the National Natural Science Foundation of China(Grant Nos.11873058,and 12133004)the National SKA Program of China(Grant No.2020SKA0120200)。
文摘The Five-hundred-meter Aperture Spherical radio Telescope(FAST)is the most sensitive radio telescope for pulsar observations.We make polarimetric measurements of a large number of faint and distant pulsars using the FAST.We present the new measurements of Faraday rotation for 134 faint pulsars in the Galactic halo.Significant improvements are also made for some basic pulsar parameters for 15 of them.We analyse the newly determined rotation measures(RMs)for the Galactic magnetic fields by using these 134 halo pulsars,together with previously available RMs for pulsars and extragalactic radio sources and also the newly determined RMs for another 311 faint pulsars which are either newly discovered in the project of the Galactic Plane Pulsar Snapshot(GPPS)survey or previously known pulsars without RMs.The RM tomographic analysis in the first Galactic quadrant gives roughly the same field strength of around 2μG for the large-scale toroidal halo magnetic fields.The scale height of the halo magnetic fields is found to be at least 2.7±0.3 kpc.The RM differentiation of a large number of pulsars in the Galactic disk in the Galactic longitude range of 26°<l<90°gives evidence for the clockwise magnetic fields(viewed from the north Galactic pole)in two interarm regions inside the Scutum arm and between the Scutum and Sagittarius arm,and the clockwise fields in the Local-Perseus interarm region and field reversals in the Perseus arm and beyond.
基金the National Natural Science Foundation of China.
文摘Average pulse profiles of pulsar signals are analyzed using the bispectrum tech-nique. The result shows that there are nonlinear phase couplings between the two frequency axes of the bispectrum charts, which indicate nonlinear factors in the generation and prop-agation of pulsar signals. Bispectra can be used as feature vectors of pulsar signals because of their being translation invariant. A one-dimension selected line spectrum algorithm for ex-tracting pulsar signal characteristic is proposed. Compared with selected bispectra, the pro-posed selected line spectra have the maximum interclass separability measurements from the point of view of the whole one-dimension feature vector. Recognition experiments on several pulsar signals received at several frequency bands are carried out. The result shows that the selected line spectrum algorithm is suitable for extracting pulsar signal characteristics and has a good classification performance.
基金supported by theNational Key Research and Development Program ofChina (2016YFA0400803)the National Natural Science Foundation of China (NSFC) (Grant Nos. 11333004,11773015 and 11573016)+1 种基金Project U1838201 supported by NSFC and CASthe Program for Innovative Research Team (in Science and Technology) at the University of Henan Province
文摘We employ the supernova fallback disk model to simulate the spin evolution of isolated young neutron stars(NSs). We consider the submergence of the NS magnetic fields during the supercritical accretion stage and its succeeding reemergence. It is shown that the evolution of the spin periods and the magnetic fields in this model is able to account for the relatively weak magnetic fields of central compact objects and the measured braking indices of young pulsars. For a range of initial parameters, evolutionary links can be established among various kinds of NS sub-populations including magnetars, central compact objects and young pulsars. Thus, the diversity of young NSs could be unified in the framework of the supernova fallback accretion model.
基金Supported by the National Natural Science Foundation of China
文摘We model the evolution of the spin frequency's second derivative ν¨ and the braking index n of radio pulsars with simulations within the phenomenological model of their surface magnetic field evolution, which contains a long-term power-law decay modulated by short-term oscillations. For the pulsar PSR B0329+54, a model with three oscillation components can reproduce its ν¨ variation. We show that the "averaged" n is different from the instantaneous n, and its oscillation magnitude decreases abruptly as the time span increases, due to the "averaging" effect. The simulated timing residuals agree with the main features of the reported data. Our model predicts that the averaged ν¨ of PSR B0329+54 will start to decrease rapidly with newer data beyond those used in Hobbs et al. We further perform Monte Carlo simulations for the distribution of the reported data in |ν¨| and |n| versus characteristic age τcdiagrams.It is found that the magnetic field oscillation model with decay index α = 0 can reproduce the distributions quite well. Compared with magnetic field decay due to the ambipolar diffusion(α = 0.5) and the Hall cascade(α = 1.0), the model with no long term decay(α = 0) is clearly preferred for old pulsars by the p-values of the two-dimensional Kolmogorov-Smirnov test.
基金supported by the National Natural Science Foundation of China(Grant Nos.11133002 and 11178001)
文摘Since there is a large population of massive O/B stars and putative neutron stars(NSs) located in the vicinity of the Galactic Center(GC),intermediate-mass X-ray binaries(IMXBs) constituted by an NS and a B-type star probably exist there.We investigate the evolutions of accreting NSs in IMXBs(similar to M82 X-2) with a ~ 5.2 M⊙companion and orbital period■ 2.53 d.By adopting a mildly super-Eddington rate M= 6 × 10^(-8) M⊙yr^(-1) for the early Case B Roche-lobe overflow(RLOF)accretion,we find that only in accreting NSs with quite elastic crusts(slippage factor s = 0.05) can the toroidal magnetic fields be amplified within 1 Myr,which is assumed to be the longest duration of the RLOF.These IMXBs will evolve into NS+white dwarf(WD) binaries if they are dynamically stable.However,before the formation of NS+WD binaries,the high stellar density in the GC will probably lead to frequent encounters between the NS+ evolved star binaries(in post-early Case B mass transfer phase)and NSs or exchange encounters with other stars,which may produce single NSs.These NSs will evolve into magnetars when the amplified poloidal magnetic fields diffuse out to the NS surfaces.Consequently,our results provide a possible explanation for the origin of the GC magnetar SGR 1745–2900.Moreover,the accreting NSs with s > 0.05 will evolve into millisecond pulsars(MSPs).Therefore,our model reveals that the GC magnetars and MSPs could both originate from a special kind of IMXB.
文摘Fast radio bursts (FRBs) at cosmological distances still hold concealed physical origins. Previously Liu (2018) proposes a scenario that the collision between a neutron star (NS) and a white dwarf (WD) can be one of the progenitors of non-repeating FRBs and notices that the repeating FRBs can also be explained if a magnetar formed after such NS-WD merger. In this paper, we investigate this channel of magnetar formation in more detail. We propose that the NS-WD post-merger, after cooling and angular momentum redistribution, may collapse to either a black hole or a new NS or even remains as a hybrid WDNS, depending on the total mass of the NS and WD. In particular, the newly formed NS can be a magnetar if the core of the WD collapsed into the NS while large quantities of degenerate electrons of the WD compressed to the outer layers of the new NS. A strong magnetic field can be formed by the electrons and positive charges with different angular velocities induced by the differential rotation of the newborn magnetar. Such a magnetar can power the repeating FRBs by the magnetic reconnections due to the crustal movements or starquakes.