New evidence of the relic nature of the general magnetic fields of
As a result of the analysis of long-term observations carried out on the 6-m telescope and the published data, we have obtained new evidence that the strongest and most complex magnetic fields in CP-stars are observed only among the relatively young objects of this group. This indicates the relic mechanism of their formation and the absence of field generation when these objects are in the Main Sequence.
(Contact - I.I.Romanyuk)
Published: Astrophysical Bulletin, 2012, Volume 67, Issue 2, and other publications
On the role of the reflection of the emission of white dwarfs on
the surfaces of their cool companions in cataclysmic systems
Using the methods of modeling of the photometric light curves and the moderate-resolution spectra obtained at the 6-m telescope, the 1-m telescope Ceiss-1000, and the 1.5-m Russian-Turkish telescope, we have studied three pre-cataclysmic variables at different stages of their evolution (from 30 thousand to 6 million years after the common-envelope stage). We refined the fundamental parameters of the components, the orbital periods, and the conditions of photospheric heating of the secondary component by the ultraviolet radiation of the hot component. It was shown that the amplitude of the photometric variability of the systems and the formation of emission spectra are caused mostly by the reflection of the radiation emitted by white dwarfs on the surfaces of their cool companions under conditions close to local thermodynamic equilibrium. Individual properties of the studied systems are determined by the effects of turbulent motions and the spottedness of the atmospheres of the secondary components.
In collaboration with KFU
(Contact - N.V.Borisov)
Published: Astronomy Reports, 2012, Vol.56, Issue 6, pp.456-462; Vol.56, Issue 6, pp.441-455; Vol.56, Issue 11, pp.867-877
Physical parameters and dynamical properties of the multiple system i UMa
One of the multiple systems suspected of instability is the quadruple star i Uma, for which a set of speckle interferometric observations was carried out on the 6-m telescope. The orbital parameters of the subsystems, the spectral types, the absolute magnitudes and the masses of the components were refined. The companion in the close subsystem Aa is most likely a white dwarf. The Aa subsystem has a probable period of 12.2 years and eccentricity of about 0.6. The orbital parameters of the subsystem BC with a 39.7 year period and 0.3 eccentricity need to be updated, although they are unlikely to change much. The outer subsystem Aa-BC seems to have a period of no less than 2000 years and a rather elongated orbit with an eccentricity of about 0.9. The most likely value of the period, 2084 years, may be refined in the next 10-20 years, when the system passes through periastron. We have simulated the dynamical evolution, both analytically, using the stability criteria, and numerically within the framework of the four-body problem. The conclusion about a possible instability was confirmed.
In collaboration with KFU
(Contact - E.V.Malogolovets)
Discovery of fast variability of the OH masers in W3
The analysis of the observational data for the well-known star formation region W3 (OH) obtained on the 32-m antenna of the "Svetloe" observatory in both circular polarizations has shown that practically all the profile features do not have a Gaussian shape (which implies an "unsaturated" regime of the interstellar OH masers). Most Zeeman pairs vary greatly in intensity and are quite often uncorrelated in variability. For the feature at -46 km/s, almost a sixfold increase in the intensity of the right-hand circularly polarized signal was observed on January 23, 2012 over a period of about 150s, whereas the left-hand polarized signal changed by no more than 15%. This phenomenon was not observed in masers previously. An estimate of the brightness temperature of this feature yields the maser amplification factor 4x107, which corresponds to an optical depth of 17.5. The more detailed data depend on the adopted maser "pump" model. Unfortunately, there is no unambiguity, and therefore more extensive studies are needed.
In collaboration with the Institute of Applied Astronomy of RAS
(Contact - I.V.Gosachinskij)
Optical detection of the process of the emergence of a super
soft x-ray source (SSS) in the classical nova V2468 Cygni
The process of the emergence of a super soft x-ray source (SSS) in the classical nova V2468 Cyg was recorded in the optical range. Observational evidence of stable thermonuclear burning on the white dwarf in this nova was obtained and spectroscopically confirmed. The emission modulation period was determined. Coronal lines are visible in the optical spectra during the ignition of the thermonuclear source on the surface of the white dwarf, which indicates a high temperature of the ionization source.
In collaboration with SAI MSU
(Contact - E.A.Barsukova)
On the nature of ultraluminous X-ray sources and their association
with young clusters
The observations of the star clusters associated with ultra-luminous x-ray sources (ULXs) in four galaxies on the 6-meter and VLT telescopes have shown that all the ULXs are located within 200pc of very young star clusters (younger than 5 million years). The probability of random associations of ULXs with clusters is very small (0.0000001), and is even smaller for the young stellar clusters. A conclusion was made that the progenitors of ULXs are close binary systems with the masses of the components at least 50-100 Solar masses. ULXs are "stellar mass" black holes at the stage of supercritical disk accretion. It is shown that the progenitors of ULXs were ejected from the clusters. The ejection of stars due to supernova explosions does not explain the observed ULXs, since there is insufficient time for the evolution of the stars and their transfer out of the cluster. The ejection is a result of the mechanism of multiple (3x - 4x) encounters of the stars in the cores of the clusters at the very first stages of cluster formation. The modern concepts of stellar cluster formation have been confirmed. This mechanism explains the well-known problem of the "runaway" stars in our Galaxy.
In collaboration with the University of Oulu, Finland
(Contact - S.N.Fabrika)