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A population synthesis model for the ultraviolet spectrum of the peculiar galaxy NGC 1672
Terlevich, Elena; Diaz, A. I.; Garcia-Vargas, M. L. +1 more
We present a stellar population synthesis model for the UV spectrum of the peculiar galaxy NGC 1672, computed with the use of theIUE Atlas Library of Stellar Spectra.
IUE observations of GL 644 AB (=Wolf 630) in the wavelength region 1150-1950 A, in June 1981.
Doyle, J. G.; Mathioudakis, M.
IUE short wavelength observations of the flare star Gl 644, obtained in June 1981 are presented. A flare was detected in one of the spectra as a strong increase in C IV, He II, and continuum fluxes. The electron density of the flaring plasma, determined using line ratio techniques, is 4 x 10 to the 10th/cu cm, which is an increase by a factor of 2…
UBVRI photometry of G, K, M HIPPARCOS stars.
Jordi, C.; Figueras, F.; Torra, J. +1 more
UBVRI data are presented for a set of 229 late-type stars, most of them being high proper motion stars. All these data are part of the Input Catalog planned observations for the Hipparcos mission.
EXOSAT Observations of the Rapidly Rotating Flare Star Gliese 890
Singh, K. P.; Rao, A. R.
This paper presents the first X-ray observations of the late-type dwarf flare star Gliese 890 using the low-energy (LE) and the medium energy (ME) detectors of the Exosat Observatory. A steady X-ray emission, most probably of coronal origin, is detected. No flaring activity is observed in X-ray observations. A combined spectral fit to the LE and M…
On the Interpretation of the EXOSAT Photometry of Two Hot DA White Dwarfs
Petre, Robert; Vennes, Stephane; Shipman, Harry L.
Exosat photometric observations of the hot DA white dwarfs GD 2 and EG 70 are presented and analyzed using model atmosphere and synthetic spectrum calculations. The numerical accuracy of the calculations and their impact on the reliability of the results are addressed. The optimum atmospheric parameters that explain the complete spectral coverage …
Signal-to-Noise Ratios in IUE SWP-LO Spectra of Chromospheric Emission-Line Sources
Ayres, Thomas R.
The short-wavelength-prime (SWP) detector of the International Ultraviolet Explorer should operate near the photon-counting limit, but the noise levels in flat-field images are several times higher. The exaggerated noise can be traced to the incomplete removal of the pixel-to-pixel granularity of the television frames by the prevailing spectral im…
Deviation from the Wilson-Bappu relationship in faint red dwarf stars.
Carlsson, M.; Engvold, O.; Elgaroy, O.
New observations of the Mg II h and k lines on red dwarf stars have been carried out with the International Ultraviolet Explorer observatory. It is found that several of the dwarf stars in the sample have Mg II h and k lines which are narrower than expected from the Wilson-Bappu relationship, that is established for stars brighter than M(v) about …
Activity in late-type stars. VI. Optical photometry and UV spectroscopy of the active dMe star, FK Aquarii in late 1983.
Lyons, M. A.; Butler, C. J.; Byrne, P. B.
Optical photometry and UV spectroscopy are reported for the flare/BY Dra star FK Aqr from 1983. These data are used to derive the rate of optical energy release in U-band flaring and compare it to four previous epochs. No conclusive evidence of any variation in this rate over an 8-yr interval has been found. No measurable BY Dra variations were pr…
WW Horologii : revised period and X-ray light curve.
Tagliaferri, G.; Beuermann, K.; Giommi, P. +2 more
An improved orbital period of the eclipsing AM Herculis binary WW Hor is reported, which allows the relative phasing of 1983 EXOSAT X-ray and the 1986-89 optical light curves to be established. It is found that X-rays and optical cyclotron continuum are produced by the same accreting pole on the magnetic white dwarf. In 1984, WW Hor was not detect…
Particle observations by EPA/EPONA during the outbound pass of Giotto from comet Halley and their relationship to large scale magnetic field irregularities.
Neubauer, F. M.; Ip, W. -H.; Daly, P. +5 more
The acceleration processes producing spikes seen superimposed on the general intensity time profile of energetic particles obtained with EPA/EPONA during the outbound pass of Giotto on 14/15 March 1986, are studied using complementary magnetic field data. Three different types of spikes were identified. Evidence for the ion pick-up process and pro…