Search Publications
Soft and hard X-ray variability from the accretion disk of NGC 5548.
Kaastra, J. S.; Barr, P.
EXOSAT observations of the Seyfert galaxy NGC 5548 confirm previous detections of a soft X-ray excess above a power law component. Both components show correlated variability on a typical time scale of half a day. There is evidence for a delay of the hard X-rays with respect to the soft X-rays of 1-2h. The spectral data can be explained in terms o…
Magnetic structure in cool stars. XVI. Emissions from the outer atmospheres of M-type dwarfs.
Mewe, R.; Rutten, R. G. M.; Schrijver, C. J. +2 more
Consideration is given to emission from the outer atmospheres of M-type dwarfs in several spectral lines originating from the chromosphere, the transition-region, and the soft X-ray emission from the corona. It is shown that M-type dwarfs systematically deviate from relations between flux densities in soft X-rays and chromospheric and transition-r…
The circumstellar gas around beta Pictoris. VIII. Evidence for a clumpy structure of the infalling gas.
Ferlet, R.; Vidal-Madjar, A.; Beust, H. +1 more
In a recent paper, the variable and redshifted circumstellar lines of ionized elements in the UV spectrum of Beta Pictoris were studied. The Al III doublet has been investigated, using both archival and recent IUE spectra of Beta Pic. This larger set of data is used to derive some general characteristics of the variable Al III lines. In particular…
High-Resolution Observations of Interstellar NA i and CA II Absorption Lines toward the Scorpius OB1 Association
Barlow, M. J.; Blades, J. C.; Crawford, I. A.
Observations of Na I and Ca II in absorption toward 22 stars in the Sco OB1 region, obtained at resolution R = 100,000 with a coude echelle spectrograph and 3.3-m camera on the 1.9-m telescope at Mt. Stromlo Observatory during 1986, are reported. The data are presented in extensive tables and graphs and analyzed in detail. Features discussed inclu…
IUE-ULDA/USSP - The on-line low resolution spectral data archive of the International Ultraviolet Explorer
Pasian, F.; Talavera, A.; Wamsteker, W. +8 more
The on-line IUE Uniform Low Dispersion Archive (ULDA) and the associated ULDA Support Software Package (USSP) are described. The underlying philosophy, the detailed corrections made to the data and the implementation details are summarized. The low-resolution data are made available for direct access to the astronomical community through the exist…
Evidence for a Cool Wind from the K2 Dwarf in the Detached Binary V471 Tauri
Carpenter, K. G.; Mullan, D. J.; Bruhweiler, F. C. +1 more
Evidence for mass loss from the K2 dwarf in V471 Tauri is found in the form of discrete absorption features in lines of various elements (Mg, Fe, Cr, Mn) and ionization stages (Mg I, Mg II, Fe I, Fe II). Resonant Mg II absorption indicates a mass loss rate of at least 10 to the -11th solar masses per year. The wind appears to be cool (no more than…
Rotational modulation and flares on RS Canum Venaticorum and BY Draconis.stars. X. The 1981 October 3 flare on V711 Tauri (= HR 1099).
Linsky, J. L.; Simon, T.; Neff, J. E. +5 more
We present a unique set of high resolution spectra of V71 1 Tauri = HR 1099 (G5 V + K1 IV) obtained with both the SWP and LWR cameras of lUE, together with simultaneous 6.4 GHz microwave emission and optical photometry, during a bright flare on 3 October 1981. The electron density of the flaring plasma at 6 104K was about 11011
The Active Chromosphere Binary HD 17433 (VY Arietis)
Saar, Steven H.; Barden, Samuel C.; Bopp, Bernard W. +4 more
The sixth-magnitude K star HD 17433 (VY Ari) is shown to be an active-chromosphere binary with an orbital period of 13.198 days. A photometric (rotational) period of 17.4 days is indicated by the existing photometry, implying that HD 17433 is not in synchronous rotation. In the optical, H-alpha is seen in emission, with variable profile and intens…
The absolute magnitudes of RR Lyrae stars - I. X Arietis.
Jameson, R. F.; Fernley, J. A.; Kilkenny, D. +4 more
A Baade-Wesselink analysis based on the infrared flux method of Blackwell and Shallis (1977) is used to estimate the temperature and angular diameter of X Ari at all phases of the pulsational cycle. These results are then used to determine the radius, distance, and absolute magnitude. New UV, optical and IR observations for this metal-poor star ar…
Ultraviolet flares on II Pegasi.
Doyle, J. G.; Byrne, P. B.; van den Oord, G. H. J.
UV spectroscopic observations of the RS CVn star, II Peg, were obtained in February 1983. The observations show evidence for flare activity in greatly enhanced chromospheric and transition region emission lines. The flare radiation is isolated and the electron pressures of the mean quiescent atmosphere and the two flares are derived from the inter…