SIGMA observations of two new hard X-ray and soft gamma-ray transients: GX 354-0 and Nova Persei

We report the first detection of two soft gamma ray transients GX 354-0 and Nova Persei (GRO J0422+32) by the coded-mask telescope SIGMA. Only preliminary results are presented with regard to Nova Persei while special emphasis is given to the data on GX 354-0 which has been monitored during the 1992 February–April survey of the Galactic Center. GX 354-0 underwent two flares of about two week duration and its average spectrum is well described by a thermal Bremsstrahlung model or a broken power law whereas the Nova Persei spectrum seems to be similar to the one observed for GRS 1124-684 in Musca.     

Experiments with injection of powerful plasma jet into the ionosphere

This paper describes two rocket experiments “Aelita” with high power lithium plasma injection. The results of onboard magnetometer, massspectrometer, photometer, plasma, corpuscular and ground radar measurements are given. Dynamics and structure of plasma formation are discussed.     

SIGMA observations of hard X-ray and soft gamma-ray emission from X-ray binaries

After more than two years of operation, the imaging γ-ray SIGMA telescope has accumulated several days of observation toward well known X-ray binaries. Four bright sources falling in this category have been detected so far: The pulsar GX 1+4 near the center of our galaxy, the stellar wind accreting system 4U 1700-377, and the black hole candidates Cygnus X-1 and GX 339-4. Moreover, SIGMA have observed three transients sources, which turned out to be also hard X-ray sources : The burster KS 1731-260, Tra X-1, and the Musca Nova. The properties of these systems in the SIGMA domain will be reviewed and a spectral distinction between black holes and neutron stars will be sketched.     

1E 1740.7-2942 revisited: Confirmation of its identification with the core of a double sided radio jet structure

After more than two years of successful in-orbit operations, the γ-ray coded aperture SIGMA telescope has accumulated 800 hours of live-time observations of the Galactic Center region, including the remarkable hard source identified with the X-ray source 1E 1740.7–2942. The long-term behavior of the soft γ-ray emission of 1E 1740.7–2942, as determined from the SIGMA survey, supplemented with previously available soft γ-ray data, leads to its identification with a singular radio source, which consists of a double sided radio jet emanating from a compact variable core whose variability is correlated with that of the soft γ-ray source. The compact radio core, which lies well inside the improved soft γ-ray (40–150 keV) error circle (27″ radius) derived from the high-resolution SIGMA survey, is also inside the ROSAT and TTM error circle derived respectively in the soft and hard X-ray bands.     

Numerical modeling of RadioAstron SRT temperature deformations

The results of modeling the thermal deformations of a space radio telescope’s reflecting surface are presented in the paper. Calculations were performed for the versions of the most unfavorable telescope illumination by the Sun.     

Simultaneous investigation of magnetospheric plasma and spacecraft charging

The results of magnetospheric plasma fluxes measurement in geosynchronous orbit are presented. The measurements were done onboard the geosynchronous Russian “Electro” spacecraft (SC) in 1995–1997 years. The diurnal variations of the plasma density and temperature were observed at various levels of geomagnetic activity.     

High angular resolution observations in the soft gamma-ray band with sigma

The launch in December 1989, of SIGMA, one of the main devices aboard the GRANAT spacecraft, has provided high-energy astronomers for the first time with a telescope whose imaging properties in the soft γ-ray regime match those of instruments operating in the hard X-ray band. Having examined 300 celestial fields during more than two years of successful in-orbit operations, this coded-aperture telescope, sensitive to radiation in the energy range 35 keV to 1.3 MeV, has succeeded both in disentangling severe source confusion problems and in providing firm identifications and reliable spectra of sources at soft γ-ray wavelengths. A selection of the salient scientific results obtained so far is presented, with intent to emphasize the unique contribution of a coded-mask telescope able to perform accurate images of the sky in the soft γ-ray domain.     

Formation and economic effectiveness estimation of management-engineering systems for spacecraft development

Various management-engineering systems (MES) participate in the process of conducting research and development on the creation of space vehicles and systems. They display certain generality of structure, relationships and principles of control, that enables us to transfer principles of formation and control from one system onto another. The methods proposed for investigation permit one to formulate general and specific principles of MES formation and, inferring from the analysis of network schedule of design works, obtain the algorithmic structure of automated design of space system objects. In order to increase quality and effectiveness of design works we propose to conduct studies at different stages of research and development with the account of uncertainties occurred.     

Dynamics of a rigid rotor in the NK-14ST-10 engine free power turbine with sliding bearings

A problem of increasing free power turbine (FPT) service life at the expense of a change to sliding bearings is considered. The differential equations for the rotor motion are derived with account for its design features. Also presented are the calculated data on forced vibrations of the system and the utility of FPT support updating is analyzed.     

SIGMA/GRANAT observations of hard X-ray emission from type I X-ray bursters

Unlike black hole candidate systems, accreting neutron stars seem to encounter appreciable difficulties in emitting strong hard X-ray fluxes. However, in the catalogue of the hard X-ray sources detected by SIGMA, three sources are associated with type I X-ray bursters. In this paper, we review the present status of the SIGMA observations of these three X-ray burst sources, namely X 1724-308 in the globular cluster Terzan II, KS 1731-260, and GX 354+0.