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Ultraviolet to near-infrared continuum flux distribution in the active binary RS canum venaticorum
Fabregat, J.; Reglero, V.; Gimenez, A.
We present multifrequency observations of the active binary RS CVn. Ultraviolet observations were obtained from the IUE data bank. Optical observations were made at the Observatorio del Roque de los Muchachos (La Palma), while the infrared observations were obtained at the Observatorio del Teide (Tenerife). The continuum of RS CVn shows that both …
Asymmetric winds in be stars
de Freitas Pacheco, J. A.; de Araujo, F. X.
The CIV and SiIV resonance doublets of 43 Be stars are investigated. Measurements of the equivalent widths seem to reveal a correlation between the strenght of the lines and the projected rotational velocity (v sini). it is discussed whether this result indicate that the wind region is not spherically symmetric.
Cygnus X-3: The recent X-ray period measurements and gamma-ray astronomy
van der Klis, M.
Our knowledge about the nature of Cyg X-3 is briefly reviewed, with particular emphasis on the lack of observational basis for some common assumptions about the object. Some consequences for gamma-ray astronomy are considered of the X-ray period measurements with EXOSAT, which indicate the presence of a large second period-derivative. If the orbit…
The Structure of the Broad Line Region in FAIRALL:9
Zheng, Wei; O'Brien, Paul T.
We find that the profile changes observed for the UV emission lines Lα,CIV λ1549, and MgIII λ2798, in the Seyfert 1 galaxy Fairall 9 occur mainly near the line centre for Lα andCIV and in the wings for MgIII. These results indicate that the broad line region (BLR) has a complex structure, possibly with non-spherical components.
Searches in the COS-B Gamma Ray Data-Base for Pulsations from PSR 1951+32
D'Amico, N.; Bennett, K.; Buccheri, R. +3 more
TeV and MeV gamma-rays from binary systems
Carollo, C. M.; Raubenheimer, B. C.; Buccheri, R. +4 more
We report the third consecutive detection of Vela X-1 as a source of VHE gamma-rays ( Eγ > 1 TeV) with a 99.92 % significance. The pulsed emission shows a broad sinusoidal light curve at a period similar to the X-ray value, with a large negative period derivative over the 60 days of observation. We also report our observations on Cen…
PSR 1820-11 : A binary gamma-ray pulsar
Wu, Mei; Li, Ti-pei
Significant pulsation structure in phase distribution in the 50-6000MeV gamma-rays from the direction of the binary radio pulsar PSR 1820-11 in the COS-B data was obtained using the folding algorithm. Besides the period search, a spatial analysis was Bade and a clear point-like gamma-ray image was found at the pulsar's position.
Time variability of stellar coronal sources observed by EXOSAT
Schmitt, J. H. M. M.; Pallavicini, R.
We present an overview of time variability in stellar coronal sources as observed with the EXOSAT satellite. We focus on M dwarf flare stars and we discuss both quiescent and flaring emission. We also outline recent developments in the modelling of stellar flares.
The MG II H and K Interstellar Lines in the Spectrum of the G-Type Giant HD 156854
Kondo, Y.; Shore, Steven N.; Gurzadian, G. A. +2 more
The results of the measurements and analysis of the IUE observations of the 2800 Mg II doublet in the spectrum of HD 156854, a G9 III star, are presented. The relative power of the magnesium chromosphere, R(Mg) = 0.00001, is in agreement with the known data for giants of the same class. The emission profiles of this doublet present absorption core…
The radiation environment for earth-orbiting astronomical satellites
Tranquille, C.; Daly, E. J.
The near-earth radiation environment consists primarily of geomagnetically trapped and solar flare energetic electrons and protons, together with a component of galactic cosmic rays. These charged particles give rise to a variety of physical effects which can compromise the operation of the sensitive detectors and electronics currently used to mak…