Parameters of the apparent relative orbit of the third body in the SZ Cam system

A complete set of parameters of the apparent relative orbit of the third body in the SZ Cam system is determined for the first time based on new speckle-interferometric and photometric observations of the eclipsing binary SZ Cam made with the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences and 0.5-m telescope of the Astronomical Observatory of Ural State University and published data. The mass of the third body and the distance to SZ Cam are estimated at M ₃ = 23.4M _⊙ and d = 1125 kpc, respectively. The binary nature of the third body is confirmed. It is suggested that SZ Cam is possibly not a member of the open star cluster NGC 1502 onto whose center it projects. A total of 16 new times of minima of SZ Cam are reported.     

Analysis of the light curves of SZ Cam using automatized fourier techniques

UBV light curves of the early type close eclipsing binary system SZ Cam have been investigated using recently developed frequency-domain techniques. The combination of both minima in the analysis results in a distinct methodological improvement over the single minimum method discussed hitherto. This improvement has two aspects: (i) increased accuracy of the determined elements, (ii) agreement of the results of the two-minimum method with those of the single-minimum method provides a criterion whereby the self-consistency of the underlying model with its representation of the light curve in the regions between minima by a cosine series and the empirically determined coefficients of such a series may be assessed. Such a self-consistent solution is found, and a further step towards a realistic representation is made by including the photometric perturbations. It is confirmed from these three light curves that the less massive star is overluminous. A probable tendency for the limb-darkening coefficient of the more massive star to increase with decreasing wavelength is also noted.     

Spectrographic study of the eclipsing binary system SZ Camelopardalis

Thirteen high-dispersion spectrographs of the eclipsing binary star SZ Cam have been studied with a view of determining more accurate information on: (i) the spectral type and luminosity classifications, (ii) absolute parameters for the component stars, (iii) the stellar environment of SZ Cam. The main results in these categories are as follows: (i) O9.5 Vnk, (ii)m _g=19±2M _⊙,m _s=6.5±1M _⊙;r _g=9.7±3.6R _⊙,r _s=4.8±1.7R _⊙;T _e～30000 K,T _e～23000 K; (iii) there is a local concentration of absorbing material which may reach a density of 2M _⊙ pc^?3, and the distance of the star is found to be 600±150 pc. The determined overluminosity of the secondary star and the local concentration of absorbing material are two topics which provide the basis for a discussion section.     

The UV spectrum of the binary system SZ Psc

In this paper we study the far-UV as well as the UV spectrum of the spectroscopic binary system SZ Psc in the wavelength ranges 1235–1950 Å and 2710–3090 Å, respectively, from spectra obtained with the International Ultraviolet Explorer (IUE). The UV spectrum of SZ Psc is mainly an emission spectrum. The short wavelength region includes emission lines formed from the low chromosphere to the transition region (e.g., Siiv,Civ, andNv) and also a deep and broad absorption line of Feii.The Mgii[1] resonance doublet at about 2800 Å presents a P Cygni profile and a multiple structure with two emission and two absorption satellite components. We also present the emission measure diagram in the temperature region 4.4T _e <53.     

Galileo long-term dust monitoring in the jovian magnetosphere

The Galileo spacecraft was launched in 1989, and—between 1995 and 2003—was the first spacecraft in orbit about Jupiter. The in-situ dust instrument on board was a highly sensitive impact-ionisation dust detector which measured the speed, mass and impact direction of dust particles hitting a metal target. It provided a unique 12-year record of cosmic dust in interplanetary and circumjovian space. Degradation of the instrument electronics caused by the harsh radiation environment in the inner jovian magnetosphere was recognised in various ways: the sensitivity for dust detection dropped by a factor of 7.5 between 1996 and 2003 while the noise sensitivity decreased by up to a factor of 100. Shifts in the parameters measured during dust impacts and noise events (charge amplitudes and signal rise times, etc.) required a time-dependent algorithm for noise identification. After noise removal a total of 21 224 complete data sets for dust impacts (i.e. impact charges, signal rise times, impact direction, etc.) is available from the entire Galileo mission between 1989 and 2003 (18 340 data sets from the Jupiter mission after 1996). This homogeneous data set has been used in many investigations of jovian dust published already or ongoing. Electronics degradation prevents the application of the mass and speed calibration to data obtained after 2000. Only in cases where the impact speed of grains is known by other means can grain masses be derived for later measurements. The drop of the detection sensitivity also required a time-dependent correction for fluxes of jovian dust streams, reaching a factor of 20 in 2002. We use the derived homogeneous noise-removed data set for long-term monitoring of the jovian dust streams with Galileo. The derived fluxes of dust stream particles were highly variable by about five orders of magnitude, between 3×10^-3 and and exhibited strong orbit-to-orbit variability. This extensive and valuable data set is available for further detailed investigations.     

Ibvs and the long-term monitoring of behaviour of variable stars

Roles of the Information Bulletin on Variable Stars (IBVS) in servicing some of the information needs of observers of variable stars are briefly summarized.     

18 GHz SZ Measurements of the Bullet Cluster

We present 18 GHz observations of the Bullet cluster using the Austalia Telescope Compact Array (ATCA), which show structure in the Sunyaev–Zeldovich effect; in particular, a deep, compact feature which does not correspond to any bright feature in X-ray, optical or lensing maps. In general, the relatively deeper SZE features appear to avoid the regions with the most intense X-ray emission. SZE displaced from X-ray centres implies that modeling cluster dynamics is non-trivial. The SZE distribution in the western parts of the cluster are co-spatial with the radio halo indicative of a common origin for the hot and relativistic electrons in the turbulent wake of the Bullet.     

New spectrophotometry for SZ cam (the problem of a third component)

We present the results of our spectroscopic observations of the eclipsing binary SZ Cam performed with the 1-m (Zeiss-1000) and 6-m (BTA) telescopes at the Special Astrophysical Observatory of the Russian Academy of Sciences in 2000 and 2003. Based on our results and published data, we have calculated new values for the component mass ratio, q = 0.72 ± 0.02, the radial velocity of SZ Cam relative to the Solar system barycenter, V ₀ =?10.6 ± 2.0 km s^?1, and the semi-amplitudes of the radial velocity curves for both components, K ₁ = 192.0 ± 2.6 and K ₂ = 266.4 ± 2.5 km s^?1. The orbital semimajor axes and masses of the components have been determined: α₁ = 10.4R _⊙, α₂ = 14.5R _⊙, M ₁ = 16.7M _⊙, M ₂ = 12.0M _⊙. New light elements and parameters of the radial velocity curve for the third body have been obtained. The mass of the secondary component of the third body M ₂ ^3b is discussed. Its lower limit is estimated to be M ₂ ^3b = 1.4M _⊙.     

Spectrophotometric study of the cepheids DT Cyg and SZ Tau

The effective temperatures of the cepheids DT Cyg and SZ Tau have been determined from a comparison of their spectral scans with appropriate stellar model atmospheres. Using these temperatures and an independent Wesselink radius determination, the luminosities of the stars have been determined. The pulsation masses and the evolutionary masses of the stars have been discussed.     

A discussion of long-term numerical solutions of the Jupiter-Saturn-Sun system

A detailed discussion of recent numerical studies concerning the stability of the Jupiter-Saturn-Sun system is presented.     

Hα long-term monitoring of the Be star β Cephei Aa

Papers published in recent years have contributed to resolve the enigma of the hypothetical Be nature of the hot pulsating star β Cephei. This star shows variable emission in the Hα line, typical for Be stars, but its projected rotational velocity is very much lower than the critical limit, contrary to what is expected for a typical Be star. The emission has been attributed to the secondary component of the β Cephei spectroscopic binary system.
In this paper, using both our and archived spectra, we attempt to recover the Hα profile of the secondary component and to analyse its behaviour with time for a long period. To accomplish this task, we first derive the atmospheric parameters of the primary,   T _eff= 24 000 ± 250 K  and  log  g = 3.91 ± 0.10  , and then we use these values to compute its synthetic Hα profile, and finally we reconstruct the secondary's profile disentangling the observed one.
The secondary's Hα profile shows the typical two-peak emission of a Be star with a strong variability. We also analysed the behaviour versus time of some linewidth parameters: equivalent width, ratio of blue to red peak intensities, full width at half-maximum, peak separation and radial velocity of the central depression.
The projected rotational velocity  ( v sin  i )  of the secondary and the dimension of the equatorial surrounding disc have also been estimated.     

Internet access to the web resources of a geographically distributed system of near-and deep-space monitoring

The state and speed characteristics of Web access to the first five nodes of the projected geographically distributed system of scientific monitoring of near and deep space are analyzed. The possibility of developing an architecture involving user query redirection to a caching server is studied. This will make it possible to relieve hardware communication links substantially and speed up HTTP connection time, especially for nodes linked via heavily congested Internet links.     

Physical parameters of the massive multiple system eta Orionis

Summary The bright massive object η Orionis is at the same time a totally eclipsing system, a spectroscopic triple system, a speckle triple system and a visual binary. These circumstances offer an exceptional opportunity for determining the physical parameters of massive stars. Our observations show that the published elements are wrong. We present a new determination of several parameters of the multiple system and propose new visual observations. Based on observations collected with the Swiss Telescope at the European Southern Observatory, La Silla, Chile.     

BV photometry of the short-period variable UU Cam

First BV measures of the short period variable UU Cam are presented here. Though the GCVS classification of the star as an RR Lyr variable, based on the spectrographic measures of Bond (1978), is substantially confirmed, there remains some doubts about it, as suggested by the general aspect of theB-V colour index.     

Astronomical aspects of building a system for detecting and monitoring hazardous space objects

In order to meet the practical priority of the mass detection of hazardous celestial bodies (HCBs) during the creation of a system to counteract space hazards (asteroids, comet hazards and space debris), we need clear technical requirements for the detection instruments designed (created). Specially targeted astronomical investigations into the basic properties of the HCB ensemble were conducted to specify such requirements (limitations). The paper presents these findings. As to asteroid and comet hazards, quantitative limitations on the HCB size (50 m) have been introduced and quantitative definitions of threatening and collisional HCB orbits have been proposed for the first time. It is shown that at a lead time of 30 days, it is necessary to detect HCBs at distances of about 1 AU, which corresponds to a telescope’s resolving power of V ～ 23 ^m . This entails the necessity to design wide-angle large-aperture telescopes. For detecting and monitoring space debris objects and meteoroids in the near-earth space at a time scale of about several days, faster instruments with smaller apertures but larger vision fields are efficient. An example is given of a basic design of a space-based system that takes into account the astronomical requirements discussed.