Peng Qiu-he

A possible mechanism for magnetar soft X-ray/γ-ray emission

Once the energies of electrons near the Fermi surface obviously exceed the threshold energy of the inverse beta decay, electron capture (EC) dominates inside the magnetar. Since the maximal binding energy of the P-3(2) neutron Cooper pair is only about 0.048 MeV, the outgoing high-energy neutrons (E-k(n) > 60 MeV) created by the EC can easily destroy the P-3(2) neutron Cooper pairs through the interaction of nuclear force. In the anisotropic neutron superfluid, each P-3(2) neutron Cooper pair has magnetic energy 2 mu B-n in the applied magnetic field B, where mu(n) = 0.966 x 10(-23) erg(.)G(-1) is the absolute value of the neutron abnormal magnetic moment. While being destroyed by the high-energy EC neutrons, the magnetic moments of the P-3(2) Cooper pairs are no longer arranged in the paramagnetic direction, and the magnetic energy is released. This released energy can be transformed into thermal energy. Only a small fraction of the generated thermal energy is transported from the interior to the surface by conduction, and then it is radiated in the form of thermal photons from the surface. After highly efficient modulation within the stars magnetosphere, the thermal surface emission is shaped into a spectrum of soft X-ray/gamma-rays with the observed characteristics of magnetars. By introducing related parameters, we calculate the theoretical luminosities of magnetars. The calculation results agree well with the observed parameters of magnetars.

Disk Stability of the Milky Way Near the Sun

By solving Poissons equation for logarithmic density disturbance in three-dimensional (3D) spiral galaxies, the disturbed potential can be given on the disk. Combining it with the corresponding dispersion relation, the local gravitational stability of our galaxy is discussed here. We have generalized the Toomres stability criterion to the more realistic 3D galaxy models. The generalized Toomres parameter Q near the sun is 2.08 or 2.20 for two or four armed spiral galaxy models, respectively.

A Hybrid Spin-Down Model and its Application to the Radio Quiet X-Ray Pulsar 1E 1207.4-5209

A series of newly published papers are focusing on the formation of the absorption features discovered by Chandra and XMM-Newton from the young radio quiet x-ray pulsar 1E 1207.4-5209. We try to interpret it as cyclotron absorption lines since this possibility could not be ruled out. With new development and application of a hybrid model, i.e., the magnetic dipole spin-down model combined with the neutrino cyclotron radiation spin-down model, we can easily avoid the contradiction between the normal rotation energy loss rate and the relatively lower magnetic field, and then we obtain the possible initial spin period (~0.420 s). We suppose that the progenitor of 1E 1207.4-5209 may be a white dwarf.

A New Method to Determine the Thickness of Spiral Galaxies: Apply to M31

A new method is presented to determine the thickness of spiral galaxies. Based on the rigorous solution of the Poisson equation for logarithmic density disturbance in three-dimensional spiral galaxies, we have derived an accurate dispersion relation for the stellar and gaseous disk with a finite thickness. From this relation, a new method is put forward here for determining the thickness of galaxies. We apply this way to M31 and get the thickness of about 0.7 kpc, which is in good agreement with the previous results.

The observed evidence of both invalidating black hole model at the galactic center and magnetic monopole existence

According to an abnormally strong radial magnetic field near the GC detected in 2013, we first demonstrate that the radiations observed from the region neighbor of the Galactic Center (GC) are hardly emitted by the gas of accretion disk which is prevented from approaching to the GC by the abnormally strong radial magnetic field. These radiations cannot be produced by the black hole at the center. Secondly, we demonstrate that the abnormally strong radial magnetic field near the GC discovered in 2013 is hardly produced by the α -turbulence dynamo mechanism which is the known most effective dynamo mechanism up to now. The dilemmas of both the black hole model at the GC and the discovery that very strong radial magnetic field in the neighbor of the GC are naturally solved in our model of supermassive object with magnetic monopoles (SMOM) proposed by Peng and Chou at 2001, in which five predictions had been proposed. Three of these predictions are quantitatively confirmed by later astronomical observations. Thus, we believe that the discovery of abnormally strong radial magnetic field near the GC is probably just the astronomical observational evidence for magnetic monopole existence which is predicted in particle physics. The conclusions of the paper are: (1) It could be an astronomical observational evidence of the existence of magnetic monopoles which it predicated in particle physics; (2) The black hole model of the GC is invalid; (3) The radiations emitted from the region near the GC may be naturally explained by our model and then our model containing magnetic monopoles could be a reasonable one.

A Possible Mechanism for the Origin of Ultrastrong Magnetic Field of Magnetars

Growing observations reveal that soft gamma-ray repeaters and anomalous x-ray pulsars are magnetars. Their magnetic fields may achieve 1014−1015 G. We explore the origin of the superstrong magnetic field by considering the magnetization of the 3P2 superfluid neutrons inside neutron stars (NSs). By solving the Tolman–Oppenheimer–Volkov equations together with the equation of state adopted by Elgaroy et al. [Phys. Rev. Lett. 77 (1996) 1428] in the calculation of the neutron pairing gap, we specifically calculate the NS internal structure, the permissible region for 3P2 superfluid neutrons inside the NS, and the total magnetic moment contributed by the orderly arranged neutron vortexes. The result shows that the induced magnetic field may cover a wide range, which is consistent with the magnetic field predicted by the standard magnetic dipole radiation for pulsar spindown.

Electron capture in fp shell at presupernova stage

The electron capture of neutron-rlch nuclei in fp shell in massive stars at presupernova stage is discussed based on the nuclear shell model. The Gamow-Teller resonance transition strength is modified by introducing a Gaussian function. As a result, the electron capture rate in high density is evidently larger than the previous results given by some authors.The electron capture of neutron-rich nuclei in fp shell in massive stars at presupernova stage is discussed based on the nuclear shell model. The Gamow-Teller resonance transition strength is modified by introducing a Gaussian function. As a result, the electron capture rate in high density is evidently larger than the previous results given by some authors.

On the Stability of a Magnetized Disk with a Massive Corotating Halo

The effects of magnetic fields on the stability of a differentially rotating disk are considered in the shearing sheet approximation. An explicit stability criterion is derived in terms of Toomres Q value and the field strength. The combined effects of both magnetic fields and a corotating dark matter halo are briefly discussed.

The influence of electron screening on electron capture at the presupernova stage

Abstract The influence of electron screening on electron capture in the shell model for the most important nuclei of electron fraction change in pre-supernovae is discussed. The decreasing rate of electron fraction is multiplied by a factor of about 0.8 ∼ 0.9 due to the electron screening.

Group Velocity of the Density Waves in Galactic Disks

This letter is emphasized on the discussion of the group velocity of disturbed galactic density waves (GDW), which is one of the two most insurmountable problems in the density waves theory. In our calculation, we find that the galactic thickness has an important effect on the GDW. The dynamic time scale of GDW in our three-dimensional model can be prominently prolonged, from 36% to 60% contrasting to that of two-dimensional galactic model. However, it is still less than the lifetime of our Galaxy, which means that it is necessary to seek some other physical mechanisms to excite and sustain the GDW.