Search Publications
Missions
Journals
Publication Years
An extended X-ray low state from Hercules X-1
Pietsch, W.; Parmar, A. N.; White, N. E. +4 more
Hercules X-1 exhibits a 35-day cycle in its X-ray intensity1,2 in addition to its pulsar rotational and orbital periodicities of 1.24 s and 1.7 days respectively. The effects of X-ray heating on the companion are visible throughout the 35-day cycle3, suggesting that the observed intensity modulation is caused by periodic bloc…
The optical spectrum of hydrogen at 160-350 million gauss in the white dwarf GRW +70 8247.
Liebert, J.; Stockman, H. S.; Angel, J. R. P.
Spectra from the magnetic white dwarf Grw +70 deg 8247 are compared with Roesner et al's. (1984) hydrogen spectrum up to 10 to the 9th G. It is noted that nearly all definite absorption features coincide with transitions whose energy is stationary or nearly stationary, with field strength in the 1.6 to 3.5 X 10 to the 8th G range. The complex spec…
Stellar activity in synchronized binaries. I. Dependence on rotation.
Walter, F. M.; Basri, G.; Laurent, R.
The authors have examined a large sample of late-type binaries with orbital periods from 1 to 100 days for relationships between stellar activity and rotation period, which is assumed to be synchronized with the stellar orbital period. Most of the systems are in the RS Canum Venaticorum class of close binaries. The activity diagnostics were observ…
The ejection of shells in the stellar wind of the hypergiant P Cygni (B1Ia+).
Lamers, H. J. G. L. M.; Cassatella, A.; Korevaar, P.
Radial velocity variations of six Fe II and six Fe III lines in the UV spectrum of the hypergiant star P Cygni (HD 193237) are studied in 33 high resolution IUE spectra, obtained over an interval of more than 5 yr. The Fe II lines have a stable component at -206±2 km s-1 which did not vary in velocity nor in strength in 5 yr. There are …
A study of ultraviolet spectra of zeta Aurigae/VV Cephei systems. VII. Chromospheric density distribution and wind acceleration region.
Schroeder, K. -P.
Chromospheric eclipse spectra have been obtained for three Zeta Aurigae binary systems using the International Ultraviolet Explorer (IUE) spacecraft. In order to fit average density models to the chromospheres, 3 samples of column densities (for 31 Cygni, 32 Cygni, and Zeta Aurigae K giants) were used. Wind velocities were derived assuming a conti…
The ultraviolet spectra of intermediate-redshift quasars.
Huggins, P. J.; Kinney, A. L.; Bregman, J. N. +1 more
In the present sample of 21 intermediate redshift quasars, for which IUE Lyman-alpha line flux and UV continuum observations have been conducted, an extrapolation of the continuum to the X-ray region is noted to fall at least 2-sigma above the measured X-ray flux, at 2 keV, for two-thirds of the sample. The strength of Lyman-alpha is well correlat…
The explanation of the 1400 and 1600 A features in DA white dwarfs.
Koester, D.; Weidemann, V.; Vauclair, G. +1 more
The authors present new IUE observations of 4 cool DA white dwarfs together with additional data for 8 objects from the literature. All objects show absorption features near 1400 and/or 1600 Å, which were already noted by other authors. These features are explained as due to quasi-molecular absorption of the H2 (1600 Å) resp. H2
Peculiar motions and star formation in the interacting galaxy complexMK 171 = NGC 3690+IC 694.
Lequeux, J.; Augarde, R.
Spectroscopic observations in the visible and in the far ultraviolet are combined with other existing information to interpret the properties of the exceptionally active extended star formation in Mk 171. The authors show that this system corresponds to the interaction, and probably to the direct collision, of two galaxies with a total mass of ⪉4×…
Identification of the 1400 and 1600 A features observed in the ultraviolet spectra of DA white dwarfs
Nelan, E. P.; Wegner, G.
The λ1600 absorption feature in the spectra of cool DA white dwarf stars has been identified as a resonance broadening of Lyα due to the hydrogen quasi molecule. Likewise, the λ1400 absorption feature in the spectra of cool and moderately warm DA white dwarf stars appears to be due to a Lyα satellite line arising from the hydrogen ion quasi molecu…
Investigation of a wind model for cataclysmic variable ultraviolet resonance line emission.
Verbunt, F.; Drew, J.
The present investigation of ionization and thermal structure in a spherically symmetric, radiatively driven wind emanating from the vicinity of a cataclysmic variable's white dwarf notes that wind ionization is always high for plausible wind and radiation field parameter values, and that resonance scattering dominates line formation at large radi…