共查询到20条相似文献，搜索用时 562 毫秒
1.
Probhas Raychaudhuri 《Astrophysics and Space Science》1972,19(2):297-301
The suggestion that the less massive star will reach the Main Sequence stage earlier than the massive star due to the effect of neutrino emission according to the photon-neutrino coupling theory is supported by the observed behaviour of H-R diagram of irregular nebular variables. After reaching the Main Sequence stage the star should pulsate with a period due to the effect of neutrino emission which may be a possible explanation of other properties of irregular nebular variables. 相似文献
2.
Sushen Kumar Saha 《Astrophysics and Space Science》1971,12(2):493-500
The neutrino bremsstrahlung process is studied here according to the photon-neutrino weak coupling theory by considering the electrons as relativistic and degenerate and by adding some lattice effects at high density. The neutrino energy loss rate due to the process is then compared with that obtained according to the current-current coupling theory. It is concluded that the process is important only in cases of high dense stars when the temperature is below 107K. 相似文献
3.
Probhas Ray Chaudhuri 《Astrophysics and Space Science》1971,12(2):325-328
The spectroscopic determination of the helium abundance in the oldest stars of the galaxy is supported by the theory of stellar evolution when neutrino emission is considered according to the photon-neutrino coupling theory, if it is assumed that the population II stars started their life with a low surface helium content.Receipt delayed by postal strike in Great Britain. 相似文献
4.
Probhas Raychaudhuri 《Astrophysics and Space Science》1972,18(2):425-436
It is pointed out that the magnetic field of a star is originated from dynamo action associated with the stellar evolution. The magnetic field of a star is related with how much nuclear energy is generated in its phase of evolution. From this we can explain why some stars possess a magnetic field high than that of the Sun. In our case the magnetic field of the star is a by-product of the stars evolution and it has no influence on the internal structure of the star but it does have influence on the flare, chromosphere and coronal activities of the star. Again it is stressed that to confirm the activities of the star, the details of evolution of stars should be calculated according to the photon-neutrino coupling theory. 相似文献
5.
Alexander Y. Potekhin Gilles Chabrier Dmitry G. Yakovlev 《Astrophysics and Space Science》2007,308(1-4):353-361
Strong (B?109 G) and superstrong (B?1014 G) magnetic fields profoundly affect many thermodynamic and kinetic characteristics of dense plasmas in neutron star envelopes. In particular, they produce strongly anisotropic thermal conductivity in the neutron star crust and modify the equation of state and radiative opacities in the atmosphere, which are major ingredients of the cooling theory and spectral atmosphere models. As a result, both the radiation spectrum and the thermal luminosity of a neutron star can be affected by the magnetic field. We briefly review these effects and demonstrate the influence of magnetic field strength on the thermal structure of an isolated neutron star, putting emphasis on the differences brought about by the superstrong fields and high temperatures of magnetars. For the latter objects, it is important to take proper account of a combined effect of the magnetic field on thermal conduction and neutrino emission at densities ρ?1010 g?cm?3. We show that the neutrino emission puts a B-dependent upper limit on the effective surface temperature of a cooling neutron star. 相似文献
6.
We present the results of numerical simulations of stationary, spherically outflowing, e ± pair winds, with total luminosities in the range 1034–1042 ergs s?1. In the concrete example described here, the wind injection source is a hot, bare, strange star, predicted to be a powerful source of e ± pairs created by the Coulomb barrier at the quark surface. We find that photons dominate in the emerging emission, and the emerging photon spectrum is rather hard and differs substantially from the thermal spectrum expected from a neutron star with the same luminosity. This might help distinguish the putative bare strange stars from neutron stars. 相似文献
7.
The constraints on the properties of neutron star matter from the mass of neutron star PSR J1614-2230 are examined in the framework of the relativistic mean field theory. We find that there are little differences between the σ potentials of large mass neutron star and those of canonnical mass neutron star. For potentials of ω, ρ, neutrons and electrons, the values corresponding to the large mass neutron star are larger than those to the canonnical mass neutron star as the baryon number density is more than a certain value. We also find that for the relative particle number density of electrons, muons, neutrons and protons and the pressure of the neutron star, the values corresponding to the large mass neutron star are far larger than those to the canonnical mass neutron star. For the relative particle number density of hyperons Λ, Σ?, Σ0, Σ+ and Ξ?, the values corresponding to the large mass neutron star are far smaller than those to the canonnical mass neutron star. These mean that the larger mass of neutron star is more advantageous to the production of protons but is not advantageous to the production of hyperons. 相似文献
8.
G. S. Sahakian 《Astrophysics》2000,43(1):111-126
The theory of pulsar radio emission has been developed in a series of our papers since 1992. It was shown that pulsar radio
emission is produced in the lower part of a channel of open magnetic field lines, in a region with a height h ≈ 1.1-107 μ
30
1/3
/P4/21 cm above a magnetic cap of the neutron star (P is the pulsar’s period and μ is the star’s magnetic moment). Here, owing to
vigorously occurring processes (the production of photons of curvature radiation and their annihilation into e+e- pairs), two ultrarelativistic particle fluxes are formed: an electron flux moving upward and a positron flux falling onto
the star’s magnetic cap. These main fluxes are accompanied by narrow strips of positron and electron fluxes of relatively
low energy, the curvature emission from which is a strong coherent radio source. The present paper is a review of earlier
papers, and important additions and refinements are also made. Equations are offered for the radio luminosity of a pulsar,
the solid angle of the radio beam, and the magnetic moment and moment of inertia of the pulsar’s neutron star.
Translated from Astrofizika, Vol. 43, No. 1, pp. 147-169, January–March, 2000. 相似文献
9.
It is suggested that recurrent and nonrecurrent geomagnetic disturbances which are related to the release of solar magnetic energy in the form of unipolar and bipolar magnetic regions respectively, are connected with the variations in the solar energy source. The true beginning of the solar cycle takes place when unipolar magnetic regions start to develop, i.e, when nuclear energy generation becomes dominant over the neutrino energy loss according to the photon-neutrino coupling theory. 相似文献
10.
Osmi Vilhu 《Astrophysics and Space Science》1974,27(2):513-515
The effect of the photon-neutrino coupling theory, developed by Bandyopadhyay (1968), on stellar structure is studied by constructing a chemically homogeneous model of one solar mass in thermal equilibrium, and taking into account the neutrinos according to the theory. As anticipated, the effect is large and leads to great difficulties in the understanding of stellar constitution. 相似文献
11.
The local correlation between far-infrared (FIR) emission and radio-continuum (RC) emission for the Small Magellanic Cloud (SMC) is investigated over scales from 3 kpc to 0.01 kpc. Here, we report good FIR/RC correlation down to ～15 pc. The reciprocal slope of the FIR/RC emission correlation (RC/FIR) in the SMC is shown to be greatest in the most active star forming regions with a power law slope of ～1.14 indicating that the RC emission increases faster than the FIR emission. The slope of the other regions and the SMC are much flatter and in the range of 0.63–0.85. The slopes tend to follow the thermal fractions of the regions which range from 0.5 to 0.95. The thermal fraction of the RC emission alone can provide the expected FIR/RC correlation. The results are consistent with a common source for ultraviolet (UV) photons heating dust and Cosmic Ray electrons (CRe?s) diffusing away from the star forming regions. Since the CRe?s appear to escape the SMC so readily, the results here may not provide support for coupling between the local gas density and the magnetic field intensity. 相似文献
12.
Leonard C. Rosen 《Astrophysics and Space Science》1969,5(2):150-170
The composition of neutron star atmospheres is calculated as a function of time including effects of diffusion, cooling and thermonuclear reactions. A seven-component nuclear reaction network with includes He4, C12, O16, Ne20, Mg24, Si28 and Fe56 is utilized. Neutron star models with different initial nuclear abundances are compared as to subsequent nucleosynthesis. It is found that the final abundances are independent of original composition assuming He4 as the major initial constituent. The final composition of the atmosphere is predominantly Fe56. Mass loss from an evolving neutron star is examined as a possible source of cosmic rays. It is found that a neutron star contributes only Fe56 significantly to the cosmic-ray spectrum. 相似文献
13.
A. E. Shtykovsky A. A. Lutovinov V. A. Arefiev S. V. Molkov S. S. Tsygankov M. G. Revnivtsev 《Astronomy Letters》2017,43(3):175-185
We present the results of the spectral and timing analysis of the X-ray pulsar LMC X-4 based on data from the NuSTAR observatory in the broad X-ray energy range 3–79 keV. Along with a detailed analysis of the source’s averaged spectrum, high-precision spectra corresponding to different phases of the neutron star spin cycle have been obtained for the first time. The Comptonization model is shown to describe best the source’s spectrum, and the evolution of its parameters as a function of the pulse phase has been traced. For all spectra (the averaged and phase-resolved ones) in the energy range 5–55 keV we have searched for the cyclotron absorption line. The derived upper limit on the optical depth of the cyclotron line τ ~ 0.15 (3σ) points to the absence of this feature in the given energy range, which provides a constraint on the magnetic field of the neutron star: B <3 × 1011 or >6.5 × 1012 G. The latter constraint is consistent with the magnetic field estimate obtained by analyzing the pulsar’s power spectrum, B ? 3 × 1013 G. Based on our analysis of the phase-resolved spectra, we have determined the delay between the emission peaks and the equivalent width of the fluorescent iron line. This delay depends on the orbital phase and is apparently associated with the travel time of photons between the emitting regions in the vicinity of the neutron star and the region where the flux is reflected (presumably in the inflowing stream or at the place of interaction between the stream and the outer edge of the accretion disk). 相似文献
14.
Qi Zhan-qiang Ding Wen-bo Zhang Cheng-min Hou Jia-wei 《Chinese Astronomy and Astrophysics》2018,42(1):69-80
By the relativistic mean field theory and relevant weak-interactional cooling theory, the relativistic cooling properties in the conventional and hyperonic neutron star matter are studied. Also a comparison between the relativistic and non-relativistic results after taking consideration of the gravity correction is performed. The results show that the relativistic effect of neutrino emission reduces the neutrino emissivity, luminosity, and the cooling rate of stellar objects, in comparison with the non-relativistic case. In the neutron star matter without hyperon, the amplitude of the cooling rate reduction caused by the relativistic effect is maximal after taking the gravity correction into consideration, it attains 56% for a 2 M⊙ neutron star composed of conventional neutron star matter, and in the hyperonic matter the amplitude of reduction is minimal, about 38%. 相似文献
15.
16.
T. N. Rengarajan 《Astrophysics and Space Science》1972,17(1):65-68
It is shown that radio emission from pulsars is unlikely to be of coherent synchrotron origin if the surface magnetic field of the central neutron star is greater than 108 G. 相似文献
17.
The source responsible for the soft x-ray excess in the emission spectrum of the pulsar RX J1037.5-5647 is associated with
a hot spot on the surface of the neutron star near the base of an accretion column. The intensity of the emission from this
source, however, only undergoes small (on the order of 15%) variations, while the intensity of the hard component varies substantially
with the rotation period of the neutron star. We show that this situation can occur if the angle between the axis of rotation
and the magnetic axis of the neutron star is no more than 8°. The variation in the intensity of the hard component of the
radiation in this case is interpreted in terms of an anisotropy in the directional diagram. In this scenario, the angle of
inclination of the orbit of the binary system is close to 10°. 相似文献
18.
Joseph D. Gelfand 《Astrophysics and Space Science》2007,308(1-4):39-42
On 27 December 2004, just the third giant flare was observed from a magnetar, in this case SGR 1806-20. This giant flare was
the most energetic of the three, and analysis of a Very Large Array observation of SGR 1806-20 after the giant flare revealed
the existence of a new, bright, transient radio source at its position. Follow-up radio observations of this source determined
that initially, this source underwent a mildly relativistic one-sided expansion which ceased at the same time as a temporary
rebrightening of the radio source. These observational results imply that the radio emission is powered by ∼1024 g of baryonic material which was ejected off the surface on the neutron star during the giant flare.
相似文献
19.
Huan-yu Jia Bao-xi Sun Jie Meng En-guang Zhao 《Chinese Astronomy and Astrophysics》2002,26(4):901-413
Neutron stars are studied in the framework of the relativistic mean field theory of interacting nucleons, hyperons, and mesons. Within the hadronic freedom, the cores of neutron stars are found to be dominated by hyperons when the density is sufficiently high. The influence of hyperon coupling constants on the transition from a neutron star to a hyperon-dominated strange neutron star is also investigated. It is found that the transition density gets its minimum value when the ratio of hyperon coupling constant to nucleon's takes the value of 0.65, and the calculated maximum mass of the neutron star is 1.4 M which lies within the range of the observational results. 相似文献
20.
The hypothesis of the relativistic beaming of pulsar emission is discussed in connection with objections advanced by Manchesteret al. (1973). It is shown that the same pulse duration of some pulsars with the non-power-law spectrum over a wide frequency interval may be associated either with large source sizes in longitude, or with location of the emitting source at various distances from the rotation axis of the neutron star (depending on the emission frequency). 相似文献