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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. 相似文献
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Y. Frémat P. Lampens H. Hensberge 《Monthly notices of the Royal Astronomical Society》2005,356(2):545-556
DG Leo is a spectroscopic triple system composed of three stars of late-A spectral type, one of which was suggested to be a δ Scuti star. Seven nights of observations at high spectral and high time-resolution at the Observatoire de Haute-Provence with the ELODIE spectrograph were used to obtain the component spectra by applying a Fourier transform spectral disentangling technique. Comparing these with synthetic spectra, the stellar fundamental parameters (effective temperature, surface gravity, projected rotation velocity and chemical composition) are derived. The inner binary consists of two Am components, at least one of which is not yet rotating synchronously at the orbital period though the orbit is a circular one. The distant third component is confirmed to be a δ Scuti star with normal chemical composition. 相似文献
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Observations of solar radio emission at 3 cm wavelength have been made at Japal-Rangapur Observatory for 1980–1981, the solar maximum year using the 3 m radio telescope. The correlation between microwave solar emissions and the sunspot activity on monthly basis has been found to be high during the maximum phase and in the high cm wavelength band. The basic component has been estimated statistically for successive solar rotations using the data obtained at Japal-Rangapur Observatory. Further, this was compared with the data obtained at other cm wavelengths during 1980–1981 and the solar minimum period 1975–1976 of the 21st cycle. The comparison showed pronounced dips in flux levels at different wavelengths during the summer months of the solar maximum year which may be attributed to the presence of coronal holes in the various levels of the solar atmosphere. The computed basic component values showed pronounced variation at high cm wavelengths for the solar maximum period with dissimilar variations at different wavelengths. During the solar minimum period the variations were negligibly small and showed more or less constant level of activity.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984. 相似文献
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We present relative astrometry and differential photometry measurements for a sample of nearby southern orbital binaries making use of the technique of Adaptive Optics. The observations were made in December 2000, with the ADONIS camera mounted at the 3.6‐m ESO telescope from La Silla Observatory, equipped with the broad‐band near‐infrared filters (J ‐, H ‐, K ‐passbands). Our sample contains stars which do not fit very well the empirical mean mass‐luminosity relation (according to our previous study), but for which accurate parallaxes (determined by the Hipparcos satellite) and high‐quality orbits were available thanks to many previous efforts. We derived accurate positions and J, H, K magnitudes of the individual components of those binaries. The individual stellar components have near‐infrared colour indices well grouped in those plots and are comparable to standard single stars. The data reduction procedure used for deriving those results is described in detail. It is based on a least‐squares fit of Moffat‐Lorentz profiles in direct imaging for well‐resolved systems and on Fourier analysis for very close pairs. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
5.
D. Mkrtichian S.-L. Kim A. V. Kusakin E. Rovithis-Livaniou P. Rovithis P. Lampens P. van Cauteren R. R. Shobbrook E. Rodriguez A. Gamarova E. C. Olson Y. W. Kang 《Astrophysics and Space Science》2006,304(1-4):169-171
We present a status report on the search for pulsations in primary componants of Algols systems (oEA stars). Analysis of 21 systems with A0-F2 spectral type primaries revealed pulsations in two systems suggesting that of the order of ten persent of Algols primaries in this range are actually pulsators. 相似文献
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In this study we present the new R and I light curve solutions for the eclipsing binary systems RW CrB and VZ Leo, which for
VZ Leo is the first one in the literature. Our new observations have been analyzed using the Wilson-Devinney code from which
new geometric and photometric elements are derived. The geometry of both stars is that of a semi-detached binary system where
the secondary component fills its Roche lobe while the primary component is well inside. In the case of RW CrB, asymmetry
in the light curve was explained by a spot model. The orbital period changes of both systems were studied and the results
indicated a period decrease which can be explained by angular momentum loss. We also investigated the possibility of pulsations
of the primary components since these systems are mentioned as candidates of δ Sct type pulsation. However, a time-series analysis of the residual curves in the filter I does not indicate any evidence
of periodic light variation for both systems. Finally, we compared the results obtained for both binary stars to those of
similar systems. 相似文献
7.
S. Hekker Y. Frémat P. Lampens P. De Cat E. Niemczura O. L. Creevey J. Zorec 《Monthly notices of the Royal Astronomical Society》2009,396(3):1689-1698
A variety of physical processes leading to different types of pulsations and chemical compositions are observed between A- and F-type stars. To investigate the underlying mechanisms responsible for these processes in stars with similar locations in the Hertzsprung–Russell diagram, an accurate abundance determination is needed, among others. Here, we describe a semi-automatic procedure developed to determine chemical abundances of various elements ranging from helium to mercury for this type of stars. We test our procedure on synthetic spectra, demonstrating that our procedure provides abundances consistent with the input values, even when the stellar parameters are offset by reasonable observational errors. For a fast-rotating star such as Vega, our analysis is consistent with those carried out with other plane-parallel model atmospheres. Simulations show that the offsets from the input abundances increase for stars with low inclination angle of about 4° . For this inclination angle, we also show that the distribution of the iron abundance found in different regions is bimodal. Furthermore, the effect of rapid rotation can be seen in the peculiar behaviour of the Hβ line. 相似文献
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Now that the HIPPARCOS satellite safely revolves on his degraded orbit - after the exploit of the ESA technicians to rescue it from the faulty ignition of its apogeum boost motor - and regularly provides the information needed for reaching the initial aim of the project, one may turn to examine the possible applications of the finalHipparcos Catalogue. In the present paper, we describe how double and multiple stars have been introduced in the Input Catalogue and what may be expected from their observation. We also try to evaluate how much the final HIPPARCOS data may influence future researches on these celestial bodies and what kind of ground-based observation programmes should be conducted in order to support the space results.This paper was presented at the IAU Colloquium No. 135 (Complementary Approaches to Double and Multiple Star Research) at Pine Mountain (Georgia, USA) in April 1992 by J. Dommanget and at the Ecole de Goutelas (HIPPARCOS: Une nouvelle donné pour l'astronomie) at Boën (France) in May 1992 by P. Lampens. Extended summaries will be published in both proceedings. 相似文献
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