Yu. N. Gnedin

The appearance of polarization in radiation from hot stars due to the faraday rotation effect as a possible method of determining stellar magnetic fields

The effect of Faraday rotation is shown to lead to the appearance of linear polarization of stellar radiation scattered in an optically-thin circumstellar electron-magnetized shell, even in the case when the shell is spherical. The spectral dependence of the polarization degree is evaluated for scattering in (i) a spherically-symmetric magnetized shell with a power-law radial dependence of the electron density, and (ii) a non-spherical ellipsoidal uniform envelope. The position of maximum in the polarization spectrum permits us to determine the magnetic field magnitude on a star surface. If the rotational and magnetic axes do not coincide, the periodic variability of the polarization will be observed with the period of stellar rotation. Some Be-stars, such as γCas, 48 Lib, EW Lac, πAqr, HD 45677, X Per, are proposed as candidates to be investigated for magnetic fields, as well as some stars of the T Tau-type. This method may be also applied to supernovae shells.

INFRARED EMISSION FROM X-RAY SOURCES

The infrared emission from some X-ray sources is attributed to proton—cyclotron masering process operating near the polar regions of an accreting neutron star in a binary system.

Fourteen years of multifrequency-coordinated observations of the X-ray/Be system A 0535+26/HDE 245770

Within the framework of a very long multifrequency campaign of coordinated, and very often simultaneous, observations of the transient X-ray/Be system A 0535+26/HDE 245770, we present a summary of this large collection of data taken with IUE and ASTRON satellites as well as with many ground-based telescopes in optical and IR regions.In this paper we emphasize the study of the physics and dynamics of the mass transfer at periastron and subsequent X-ray flaring, which is a typical problem of the X-ray/Be binary system class.

Resonance Magnetic Conversion of Photons Into Massless Axions and Striking Feature in Quasar Polarized Light

The effect of massless Nambu-Goldstone bosons (massless axions) on the appearance of striking feature in QSO polarized light is suggested. This feature can be appeared in a result of resonance magnetic conversion of photons into massless axions. The resonance magnetic conversion can take place for mixture of electron plasma and neutral hydrogen gas into a magnetic field in the regions of Damped Ly-α systems. The QSOs with a noticeable Faraday rotation measures should be suitable targets for polarimetric observations.

Fast X-ray and IR variability of A 0535+262

X-ray bursts of the source A 0535+262 with a characteristic time-scale ∼ 5 min have been discovered using the observational data of the Soviet ‘Astron’ satellite obtained on 7 April, 1983. Similar temporal variations were observed in the IR range on 26 September, 1981, 26–27 October and 16–17 December, 1983. The presence of such bursts gives evidence of strong inhomogeneity in the electron shell around the optical component and an accreting flow of matter in the vicinity of the neutron star. The parameters of the inhomogeneities are estimated.

ASTRONOMICAL SEARCHES FOR NONBARIONIC DARK MATTER

Astronomical methods of searching for light Goldstone bosons (axions and arions), which are candidates for dark matter, are briefly discussed. Three processes for the coupling between axions and photons are considered: (a) the decay of axions into two photons; (b) the conversion of photons into axions in the magnetic fields of stars and interstellar and intergalactic media; (c) the inverse transformation of axions generated inside the cores of stars. The intergalactic light of clusters of galaxies and the brightness of the night sky are good candidates for searches for an emission line arising from the radiative decay of axions. The results of observations made with the 6 m telescope of the Special Astrophysical Observatory do not provide any evidence for the existence of the hadronic axion decay line. The best upper limit for the photon-axion coupling constant is derived from linear polarization observations of magnetic Ap stars.

Axion decay in a strong magnetic field and radio fluxes from magnetic white dwarfs

Radio emission of isolated magnetic white dwarfs due to invisible axions decay in a strong magnetic field is estimated. It is possible to reach theoretical limits on the abundance and coupling of cosmic axions provided that radiofluxes would be observed at the level ≲ 1 μJy.