Search Publications
Soft X-ray observations of the VELA pulsar PSR 0833-45.
Oegelman, H.; Zimmermann, H. -U.
X-ray maps produced from Exosat observations of the Vela pulsar in the 0.03-2.4 keV range confirm the components discussed by Harnden et al. (1985). Restricting the central source to a neutron star with an 8-15 km radium emitting blackbody-like radiation suggests a surface temperature in the 600,000 to 1,000,000 K. It is found that the observed bl…
Flux-flux relation : MG II H and K versus X-rays in dwarf M and K stars.
Doyle, J. G.; Mathioudakis, M.
Surface X-ray and Mg II h and k fluxes are presented for a group of dMe, dKe, dM, and dK stars. No correlation is apparent between the fluxes for the group of stars as a whole, although a good correlation is present for a subgroup, i.e., the dMe/dKe's. The Mg II and X-ray luminosities for these active stars define an upper boundary, which is depen…
Rotational modulation and flares on RS CVn and BY Draconis stars. XIII. IUE spectroscopy and photometry of II Pegasi during September 1986.
Doyle, J. G.; Rodono, M.; Butler, C. J. +3 more
UV spectroscopy obtained for the RS CVn star II Pegasi in September, 1986, indicates the presence of a rotational modulation effect for the Mg II h and k and O I 1305 A lines; the largest flux is observed when the primary spot concentration is nearly on the opposite hemisphere, and the rotational modulation is noted to be of opposite sense to that…
One-pole and two-pole X-ray emission in the AM Herculis binary BL Hyi.
Beuermann, K.; Schwope, A. D.
This paper reports the results of extensive X-ray observations of BL Hyi = H0139-68 with the Exosat satellite when the source was in states of low and intermediate brightness. In the low state, X-rays were observed only between orbital phases phi = 0.0 and about 0.4, coincident with the orbital hump of cyclotron emission from the main pole. In the…
A comparison of solar and stellar ultraviolet spectra obtained with SKYLAB and IUE.
Pallavicini, R.; Cheng, C. C.; Cerruti-Sola, M. +1 more
A comparison is presented of 78 Short-Wavelength Primary (SWP) low-resolution IUE spectra of 45 late-type stars and 10 high-resolution Skylab spectra of spatially-resolved solar regions of various degrees of magnetic activity, including quiet areas, plage regions, and one flare. The results show that the different levels of chromospheric and trans…
Coordinated observations of a large impulsive flare on UV Ceti.
Heise, J.; van Genderen, A. M.; Waelkens, C. +16 more
The characteristics of the major flare observed on UV Ceti on Decemmber 1985 at 01:26 UT during an international observing campaign are described. X-ray observations were obtained with Exosat in the 0.06-0.3 keV bands and 1-6 keV bands; optical photometry was obtained in 11 wavelength bands, and spectra were recorded in the wavelength range 3500 t…
Studies of symbiotic stars. I. Location of the UV emitting regions in6 S-type systems monitored by the IUE satellite.
Munari, U.
IUE archive low resolution short wavelength spectra for the 6 binary symbiotic stars EG Andromedae, V1329 Cygni, AG Pegasi, CI Cygni, AX Persi, and SY Muscae are investigated to locate the regions responsible of the UV emission, both lines and continuum. It is demonstrated that, in all these S-type systems, the majority of UV emission lines and co…
X-ray spectroscopy of RS CVn stars with EXOSAT.
Schmitt, J. H. M. M.; Pasquini, L.; Pallavicini, R.
Results are presented of a spectral analysis of a sample of RS CVn stars which comprises all (except two) cataloged RS CVn binaries observed by Exosat. Data from both the Medium Energy and Low Energy Exosat experiments are analyzed assuming simple spectral models and the dependence of the fitted coronal parameters on the signal-to-noise ratio. Evi…
IUE observations of the M dwarfs CM Draconis and Rossiter 137B : magnetic activity at saturated levels.
Linsky, J. L.; Vilhu, O.; Neff, J. E. +4 more
IUE observations of two active M dwarfs with known rotation rate or age and presumed to be almost totally convective are presented. The first of these stars, CM Draconis (Gl 630.1), is an old Population II binary with its components in tidally induced rapid rotation (P = 1.27 d, dM 4 + dM 4). The other one, Rossiter 137 B, forms with HD 36705 (AB …
The distance of the helium-variable B star HD 37479.
Heber, U.; Groote, D.; Hunger, K.
The gravity of HD 37479 (Sigma Ori E) is redetermined using eight high resolution and high S/N ratio spectrograms. The analysis is carried out differentially with respect to the main sequence stars Gamma Peg and Sigma Ori D. It is confirmed that the gravity of HD 37479 is log g = 3.95 + or - 0.15. Evidence is presented for a peculiar interstellar …