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 $\psi_{pr}= 0$. It shows a peculiar shape characterized by a significant excess near the orbital phase $\phi_{orb}= 0.25$, 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 $\sim 0.25$ and $\sim 0.75$, 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 $\psi_{pr}= 0$ and weak but significant secondary maximum at $\psi_{pr}= 0.6$. 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 $0.5\gtrsim q\gtrsim 0.3$, 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 $q\sim 0.3$, 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 $1.5-2$) 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 $z\approx 0.5-1$ 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

TeV Flux modulation in PSR B1259-63/LS 2883

PSR B1259-63/LS 2883 is a binary system where a 48 ms pulsar orbits a massive Be star with a highly eccentric orbit (e=0.87) with a period of 3.4 years. The system exhibits variable, non-thermal radiation visible from radio to very high energies (VHE) around periastron passage. This radiation is thought to originate from particles accelerated in the shock region between the pulsar wind (PW) and stellar outflows. The consistency of the H.E.S.S. data with the inverse Compton (IC) scenario is studied in the context of dominant orbital phase dependent adiabatic losses. The dependence of the observed TeV flux with the separation distance is analyzed. Model calculations based on IC scattering of shock accelerated PW electrons and UV photons are performed. Different non-radiative cooling profiles are suggested for the primary particle population to account for the variable TeV flux. The TeV fluxes obtained with H.E.S.S. in the years 2004 and 2007 seem to be only dependent on the binary separation. The presented results hint at a peculiar non-radiative cooling profile around periastron dominating the VHE emission in PSR B1259-63. The location of the stellar disc derived from this non-radiative cooling profile is in good agreement with that inferred from radio observations.Comment: 6 pages, 5 figures, accepted for publication in A&A on 03/09/201