Effect of superstrong magnetic fields on thermonuclear reaction rates on the surface of magnetars

A simple and efficient screening model for studying the effects of superstrong magnetic fields （such as those of magnetars） on thermonuclear reaction rates on magnetar surfaces is proposed in this paper. The most interesting thermonuclear reactions, including hydrogen burning by the CNO cycle and helium burning by the triple alpha reaction, are investigated on the surface ofmagnetars. We find that the superstrong magnetic fields can increase the thermonuclear reaction rates by many orders of magnitude. The enhancement may have a dramatic effect on the thermonuclear runaways and bursts on the surfaces of magnetars.     

Nuclear energy generation rates on magnetar surfaces

Based on the new screening model, this paper discusses the influence of superstrong magnetic fields on nuclear energy generation rates on the surface of magnetars. The obtained result shows that the superstrong magnetic fields can increase the nuclear energy generation rates by many orders of magnitude. The enhancement may have a significant influence for further study of the magnetars, especially for the cooling, the x-ray luminosity observation and the evolution of the magnetars.     

超强磁场对中子星外壳层核素56Fe,56Co,56Ni,56Mn和56Cr电子俘获过程中微子能量损失的影响

研究了超强磁场对中子星外壳层核素⁵⁶Fe,⁵⁶Co,⁵⁶Ni,⁵⁶Mn和⁵⁶Cr电子俘获过程中微子能量损失的影响.结果表明,就大部分中子星表面的磁场B<10¹³G,超强磁场对中微子能量损失率的影响很小.对于一些磁场范围为10¹³—10¹⁵G的超磁星,超强磁场可使中微子能量损失率大大降低,甚至超过5个数量级.     

Effect of Superstrong Magnetic Fields on Nuclear Energy Generation Rate in the Crust of Neutron Stars

This paper shows that superstrong magnetic fields （such as those of magnetars） can increase the energy generation rate many times in the crust of neutron stars. This result undoubtedly not only influences the cooling of neutron stars and the X-ray luminosity observed of neutron stars but also the evolution of neutron stars.     

Electron capture of nuclides 52,53,54, 55, 56Fe in magnetars

Based on the theory of relativity in superstrong magnetic fields (SMFs), we have carried out an estimation on electron capture (EC) rates of nuclides ^{52,53,54,55,56}Fe in the SMFs in magnetars. The rates of change of electronic fraction (RCEF) in the EC process are also discussed. The results show that the EC rates increase greatly and even exceeds by 4 orders of magnitude (e.g. ⁵⁴Fe, ⁵⁵Fe and ⁵⁶Fe) in SMF. On the contrary, the RCEF decreases largely and even exceeds by 5 orders of magnitude in the SMF.     

Hydrogen-like atom in a superstrong magnetic field: Photon emission and relativistic energy level shift

Following our previous work, additional arguments are presented that in superstrong magnetic fields B ? (Zα)² B ₀, B ₀ = m ² c ³/e? ≈ 4.41 × 10¹³ G, the Dirac equation and the Schrödinger equation for an electron in the nucleus field following from it become spatially one-dimensional with the only z coordinate along the magnetic field, “Dirac” spinors become two-component, while the 2 × 2 matrices operate in the {0; 3} subspace. Based on the obtained solution of the Dirac equation and the known solution of the “onedimensional” Schrödinger equation by ordinary QED methods extrapolated to the {0; 3} subspace, the probability of photon emission by a “one-dimensional” hydrogen-like atom is calculated, which, for example, for the Lyman-alpha line differs almost twice from the probability in the “three-dimensional” case. Similarly, despite the coincidence of nonrelativistic energy levels, the calculated relativistic corrections of the order of (Zα)⁴ substantially differ from corrections in the absence of a magnetic field. A conclusion is made that, by analyzing the hydrogen emission spectrum and emission spectra at all, we can judge in principle about the presence or absence of superstrong magnetic fields in the vicinity of magnetars (neutron stars and probably brown dwarfs). Possible prospects of applying the proposed method for calculations of multielectron atoms are pointed out and the possibility of a more reliable determination of the presence of superstrong magnetic fields in magnetars by this method is considered.     

速度分群情况下氘氚热核反应率的模拟与分析

研究两种原子核粒子参与反应的热核聚变,假定一种原子核粒子处于热动平衡状态,对另一种原子核粒子速度分布进行分群,推导分群热核反应率以及平均热核反应率,编制相应计算程序;以氘氚热核聚变反应为例计算分群热核反应率和相应的平均热核反应率,并与直接积分结果进行对比;同时,细致研究平均热核反应率与速度分群数目的关系.     

Magnetic collapse of a neutron gas: Can magnetars indeed be formed?

A relativistic degenerate neutron gas in equilibrium with a background of electrons and protons in a magnetic field exerts its pressure anisotropically, having a smaller value perpendicular to than along the magnetic field. For critical fields the magnetic pressure may produce the vanishing of the equatorial pressure of the neutron gas. Taking this as a model for neutron stars, the outcome could be a transverse collapse of the star. This fixes a limit to the fields to be observable in stable neutron star pulsars as a function of their density. The final structure left over after the implosion might be a mixed phase of nucleons and a meson condensate, a strange star, or a highly distorted black hole or black ”cigar”, but not a magnetar, if viewed as a superstrongly magnetized neutron star. However, we do not exclude the possibility of superstrong magnetic fields arising in supernova explosions which lead directly to strange stars. In other words, if any magnetars exist, they cannot be neutron stars. Received: 25 November 2002 / Revised version: 25 February 2003 / Published online: 5 May 2003     

Resonant nuclear reaction ~(23)Mg(p,γ) ~(24)Al in strongly screening magnetized neutron star crust

Based on the relativistic theory of superstrong magnetic fields(SMF), by using three models those of Lai(LD), Fushiki(FGP), and our own(LJ), we investigate the influence of SMFs due to strong electron screening(SES) on the nuclear reaction ~(23)Mg(p,γ) ~(24)Al in magnetars. In a relatively low density environment(e.g., ρ_7 0.01)and 1 B_(12) 10~2, our screening rates are in good agreement with those of LD and FGP. However, in relatively high magnetic fields(e.g., B_(12) 10~2), our reaction rates can be 1.58 times and about three orders of magnitude larger than those of FGP and LD, respectively(B_(12), ρ~7 are in units of 10~(12)G, 10~7 g cm~(-3)). The significant increase of strong screening rate can imply that more ~(23)Mg will escape from the Ne-Na cycle due to SES in a SMF. As a consequence,the next reaction, ~(24)Al(+β, ν) ~(24)Mg, will produce more ~(24)Mg to participate in the Mg-Al cycle. Thus, it may lead to synthesis of a large amount of A20 nuclides in magnetars.     

Effect of strong magnetic field on electron capture of iron group nuclei in crusts of neutron stars

In this paper electron capture on iron group nuclei in crusts of neutron stars in a strong magnetic field is investigated. The results show that the magnetic fields have only a slight effect on electron capture rates in a range of 10$^{8}-10^{13}$G on surfaces of most neutron stars, whereas for some magnetars the magnetic fields range from 10$^{13}$ to 10$^{18}$~G. The electron capture rates of most iron group nuclei are greatly decreased, reduced by even four orders of magnitude due to the strong magnetic field.     

Letter: Nonlinear Gravitational-Electromagnetic Bending of the Rays of Weak Electromagnetic Waves in the Fields of Pulsars and Magnetars

The eikonal equation is constructed for a weak electromagnetic wave that propagates by the laws of parameterized post-Maxwellian electrodynamics of vacuum in the magnetic dipole and gravitational fields of pulsars and magnetars. An approximate solution has been found for the equation for the rays, along which two mutually perpendicular normal modes of electromagnetic wave are propagating. The ray bending angles and time delay of the first normal mode relatively the second normal mode of the electromagnetic waves polarization states are determined as resultant from the nonlinear effect of the gravitational and magnetic dipole fields of neutron stars on the rays.     

α Decays in Superstrong Static Electric Fields

Superstrong static electric fields could deform Coulomb barriers between α clusters and daughter nuclei, and bring up the possibility of speeding up α decays. We adopt a simplified model for the spherical α emitter ²¹²Po and study its responses to superstrong static electric fields. We find that superstrong electric fields with field strengths|E|~ 0:1 MV/fm could turn the angular distribution of α emissions from isotropic to strongly anisotropic, and speed up α decays by more than one order of magnitude. We also study the influences of superstrong electric fields along the Poisotope chains, and discuss the implications of our studies on α decays in superstrong monochromatic laser fields. The study here might be helpful for future theoretical studies of α decay in realistic superstrong laser fields.     

Cold neutral plasma in a quantizing magnetic field

The chemical potential of a relativistic and an ultrarelativistic electron gas and the energy of an ultrarelativistic electron gas at T = 0 are expressed analytically as functions of the magnetic field. The possible application of these expressions to the investigation of super-compressed matter in the presence of superstrong magnetic fields is discussed.     

Neutrino energy loss by electron capture in magnetic field at the crusts of neutron stars

Based on the p-f shell model,the effect of strong magnetic field on neutrino energy loss rates by electron capture is investigated.The calculations show that the magnetic field has only a slight effect on the neutrino energy loss rates in the range of 108-1013 G on the surfaces of most neutron stars.But for some magnetars,the range of the magnetic field is 1013-1018 G,and the neutrino energy loss rates are greatly reduced,even by more than four orders of magnitude due to the strong magnetic field.     

Stellar structure of magnetars

Magnetars are strong magnetized neutron stars which could emit quiescent X-ray, repeating burst of soft gamma ray, and even the giant flares. We investigate the effects of magnetic fields on the structure of isolated magnetars. The stellar structure together with the magnetic field configuration can be obtained at the same time within a self-consistent procedure. The magnetar mass and radius are found to be weakly enhanced by the strong magnetic fields. Unlike other previous investigations, the magnetic field is unable to violate the mass limit of the neutron stars.     

Neutrino energy loss by electron capture in magnetic field at the crusts of neutron stars

Based on the p-f shell model, the effect of strong magnetic field on neutrino energy loss rates by electron capture is investigated. The calculations show that the magnetic field has only a slight effect on the neutrino energy loss rates in the range of 10⁸—10¹³G on the surfaces of most neutron stars. But for some magnetars, the range of the magnetic field is 10¹³—10¹⁸G, and the neutrino energy loss rates are greatly reduced, even by more than four orders of magnitude due to the strong magnetic field.     

Color superconducting matter in a magnetic field

We investigate the effect of a magnetic field on cold dense quark matter using an effective model with four-Fermi interactions. We find that the gap parameters representing the predominant pairing between the different quark flavors show oscillatory behavior as a function of the magnetic field. We point out that due to electric and color neutrality constraints the magnetic fields as strong as presumably existing inside magnetars might induce significant deviations from the gap structure at a zero magnetic field.     

Electron capture rates for iron group nuclei at the surface of magnetar

Effects of an ultra-strong magnetic field on electron capture rates for 55Co are analyzed in the nuclear shell model and under the Landau energy levels quantized approximation in the ultra-strong magnetic field, and the electron capture rates on 10 abundant iron group nuclei at the surface of a magnetar are given. The results show that electron capture rates on 55Co are increased greatly in the ultra-strong magnetic field, by about 3 orders of magnitude generally. These conclusions play an important role in future study of the evolution of magnetars.