Search Publications
The 1978-1995 variability of the symbiotic star AG Pegasi in the ultraviolet.
Altamore, A.; Cassatella, A.
In this paper we study in detail the variability of the symbiotic nova AG Peg in the IUE range during the period 1978-1995. We find that the luminosity of the hot component decreased steadily from about 1850Lsun_ in 1978 to 430Lsun_ in 1995 while its effective temperature remained nearly constant, 86500+/-1300K. At the same t…
Luminosity and related parameters of δ Scuti stars from HIPPARCOS parallaxes. General properties of luminosity.
Mantegazza, L.; Antonello, E.
The absolute magnitudes of δ Scuti stars derived from parallaxes measured by the Hipparcos astrometric satellite are discussed and compared with the previous estimates based on photometric uvbyβ indices. There are significant differences which are related to photometric effects of metallicity and rotational velocity, but the possible effect of a c…
Intense molecular emission from the Lagoon nebula, M8.
White, G. J.; McCaughrean, M. J.; Tothill, N. F. H. +3 more
The discovery is reported of the second strongest source of mm and submm wavelength CO line emission, towards M8, the Lagoon Nebula in Sagittarius. The ~31Msun_ molecular core has dimensions ~0.2x0.3pc and is centred on the O7V star Herschel 36 (H36), near the Hourglass Nebula in the core of M8. Emission from the CO line wings extends t…
The barium stars in the Hertzsprung-Russel diagram.
Bergeat, J.; Knapik, A.
We present absolute magnitudes for a sample of 52 barium stars observed by the HIPPARCOS satellite, and their location in the HR diagram. Our plot (Fig. 1) is restricted to stars with parallax accuracies better than 22%. The luminosity classes range from Ib supergiants down to V dwarfs on the main sequence, as expected from spectral classificaiton…
Correlation between variability time scale and X-ray spectral index in AGN.
Wilms, J.; Staubert, R.; Koenig, M.
We have analysed EXOSAT ME X-ray light curves of a sample of AGN assuming a stochastic process in these sources. The result is a significant anti-correlation between the relaxation timescale τ, derived from this stochastic model fit, and the photon index {GAMMA} of the X-ray spectrum. This establishes for the first time a relationship between vari…
An active K0 IV-V star and a hot white dwarf (EUVE J0702+129) in a wide binary.
Doyle, J. G.; Christian, D. J.; Mathioudakis, M. +1 more
We present far ultraviolet and optical spectroscopy of the Extreme Ultraviolet Explorer (EUVE) survey source EUVE J0702+129 revealing a composite K0 star plus DA white dwarf spectrum. The International Ultraviolet Explorer spectra show continuum emission from a hot white dwarf (Teff=30-40,000K) and a rising contribution from the K0 star at λ>25…
Wind variability of B supergiants. II. The two-component stellar wind of γ Arae.
Howarth, I. D.; Massa, D.; Prinja, R. K. +2 more
The stellar wind of the rapidly rotating early-B supergiant, γ Ara, is studied using time series, high-resolution IUE spectroscopy secured over ~6 days in 1993 March. Results are presented based on an analysis of several line species, including N V, C IV, Si IV, Si III, C II, and Al III. Comparisons of the time-averaged wind line morphology of γ A…
Astrometry of the globular cluster 47 Tucanae and possible optical identification of X-ray sources.
Koch-Miramond, L.; Auriere, M.; Geffert, M.
Positions of stars of 47 Tuc have been derived by the use of photographic plates and CCD frames (ESO La Silla) and data from the Hubble Space Telescope (HST). The positions have been determined with respect to the PPM, which is based on the FK5 system. We have compared the positions of variable and blue stars in the core of 47 Tuc with those of th…
Discovery of CI around 51 Ophiuchi.
Deleuil, M.; Ferlet, R.; Vidal-Madjar, A. +6 more
We present the discovery of cold CI in the 51 Oph environment, with a column density of N=5x10^13^cm^-2^ and temperature T=~20K. This is the first β Pic-like star other than β Pic with simultaneous detection of cold dust and gas. The CI/infrared continuum ratio and consequently the gas/dust ratio are similar to the β Pic ones. Since CI has a very …
Stellar activity and the Wilson-Bappu relation.
Engvold, O.; Elgaroy, O.; Joras, P.
The MgII h and k lines of 78 single stars observed with the International Ultraviolet Explorer (IUE) observatory have been analyzed. Stars of spectral classes F, G, K and M and luminosity classes I-V are represented in the sample. From these data it is shown that the Wilson-Bappu relation for the Mg II h and k lines is fulfilled over a range of 18…