Gravitational wave background from coalescing compact stars in eccentric orbits

Stochastic gravitational wave background produced by a stationary coalescing population of binary neutron stars in the Galaxy is calculated. This background is found to constitute a confusion limit within the LISA frequency band up to a limiting frequency \NUlim{}\sim 10^{-3} Hz, leaving the frequency window $\sim 10^{-3}$--$10^{-2}$ Hz open for the potential detection of cosmological stochastic gravitational waves and of signals involving massive black holes out to cosmological distances.Comment: 6 pages, 7 figure

Rapidly rotating neutron star progenitors

Rotating proto-neutron stars can be important sources of gravitational waves to be searched for by present-day and future interferometric detectors. It was demonstrated by Imshennik that in extreme cases the rapid rotation of a collapsing stellar core may lead to fission and formation of a binary proto-neutron star which subsequently merges due to gravitational wave emission. In the present paper, we show that such dynamically unstable collapsing stellar cores may be the product of a former merger process of two stellar cores in a common envelope. We applied population synthesis calculations to assess the expected fraction of such rapidly rotating stellar cores which may lead to fission and formation of a pair of proto-neutron stars. We have used the BSE population synthesis code supplemented with a new treatment of stellar core rotation during the evolution via effective core-envelope coupling, characterized by the coupling time, $\tau_c$. The validity of this approach is checked by direct MESA calculations of the evolution of a rotating 15 $M_\odot$ star. From comparison of the calculated spin distribution of young neutron stars with the observed one, reported by Popov and Turolla, we infer the value $\tau_c \simeq 5 \times 10^5$ years. We show that merging of stellar cores in common envelopes can lead to collapses with dynamically unstable proto-neutron stars, with their formation rate being $\sim 0.1-1\%$ of the total core collapses, depending on the common envelope efficiency.Comment: 10 pages, 4 figures, accepted for publication in MNRA

A young contracting white dwarf in the peculiar binary HD 49798/RX J0648.0--4418?

HD 49798/RX J0648.0--4418 is a peculiar X-ray binary with a hot subdwarf (sdO) mass donor. The nature of the accreting compact object is not known, but its spin period $P=13.2$~s and $\dot P =-2.15 \times 10^{-15}$s~s$^{-1}$, prove that it can be only either a white dwarf or a neutron star. The spin-up has been very stable for more than 20 years. We demonstrate that the continuous stable spin-up of the compact companion of HD 49798 can be best explained by contraction of a young white dwarf with an age $\sim 2$~Myrs. This allows us to interpret all the basic parameters of the system in the framework of an accreting white dwarf. We present examples of binary evolution which result in such systems. If correct, this is the first direct evidence for a white dwarf contraction on early evolutionary stages.Comment: 9 pages, accepted to MNRA

Potentials and Limitations of "Input-Output" Analysis (To the 60th Anniversary of Statistical Work in the Field of Intersectoral Research in the CIS Countries)

The article reveals the possibilities of using the Russian system of input-output tables and intersectoral models for analytical and forecasting purposes and substantiate managerial decisions in the fild of economic policy. It is shown how the input-output method's capabilities were implemented at three stages of the development of intersectoral research in Russia, taking into account the specifis of the problems being solved and the development of the statistical base. The primary attention authors paid to the current stage of developing the method and its use directions. A characteristic is given of the constraints objectively inherent in this method and the input-output tables' information system (IOT). The authors' position regarding their signifiance is expressed. A new direction in using data from the IOT system is considered — the analysis of the fial product's cost as accumulated value-added, which implies a full use of the analytical potential of modern input-output tables. Proposals are given for improving the intersectoral toolkit based on taking into account the links between production, the need for investment and the state of the production and technical base