105 research outputs found
Peculiarities in the orbital and precessional variability of SS433 from INTEGRAL observations
Based on multiyear INTEGRAL observations of SS433, a composite IBIS/ISGRI
18-60 keV orbital light curve is constructed around zero precessional phase
. It shows a peculiar shape characterized by a significant excess
near the orbital phase , which is not seen in the softer 2-10
keV energy band. Such a shape is likely to be due to a complex asymmetric
structure of the funnel in a supercritical accretion disk in SS433. The orbital
light curve at 40-60 keV demonstrates two almost equal bumps at phases and , most likely due to nutation effects of the accretion
disk. The change of the off-eclipse 18-60 keV X-ray flux with the precessional
phase shows a double-wave form with strong primary maximum at
and weak but significant secondary maximum at . A weak
variability of the 18-60 keV flux in the middle of the orbital eclipse
correlated with the disk precessional phase is also observed. The joint
analysis of the broadband (18-60 keV) orbital and precessional light curves
obtained by INTEGRAL confirms the presence of a hot extended corona in the
central parts of the supercritical accretion disk and constrain the binary mass
ratio in SS433 in the range , confirming the black
hole nature of the compact object. Orbital and precessional light curves in the
hardest X-ray band 40-60 keV, which is free from emission from thermal X-ray
jets, are also best fitted by the same geometrical model with hot extended
corona at , stressing the conclusions of the modeling of the
broad-band X-ray orbital and precessional light curves.Comment: 6 pages. 12 figures, LATeX, submitted to Proc. 9th INTEGRAL Workshop
(Paris, 15-19 October 2012). To be published in Proc. of Scienc
The evolution of relative frequencies of ONe and CO SNe Ia
In this population synthesis work we study a variety of possible origin
channels of supernovae type Ia (SNe Ia) Among them mergers of carbon-oxygen
(CO) and oxygen-neon (ONe) white dwarfs (WDs) under the influence of
gravitational waves are considered as the primary channel of SNe Ia formation.
We estimated frequencies of mergers of WDs with different chemical compositions
and distributions of masses of merging WDs. We computed the dependence of the
ratio of merger frequencies of ONe and CO WDs as primaries in corresponding
binaries on time. The scatter of masses of considered sources (up to the factor
) of SNe Ia is important and should be carefully studied with other
sophisticated methods from theoretical point of view. Our ``game of
parameters'' potentially explains the increased dimming of SNe Ia in the
redshift range by the changes in the ratio of ONe and CO WDs,
i.e., to describe the observed accelerated expansion of the Universe in terms
of the evolution of properties of SNe Ia instead of cosmological explanations.
This example shows the extreme importance of theoretical studies of problems
concerning SNe Ia, because evolutionary scenario and parameter games in nature
potentially lead to confusions in their empirical standardization and,
therefore, they can influence on cosmological conclusions.Comment: MNRAS, accepted, 12 pages, 4 figures, 1 tabl
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