Search Publications
Two patterns of correlated X-ray timing and spectral behaviour in low-mass X-ray binaries.
van der Klis, M.; Hasinger, G.
Exosat data are used to study the power spectra of 16 LMXBs as a function of their behavior in X-ray color-color diagrams. The study confirms the existence of a class of sources with three-branched Z-shaped colour-colour diagrams characterized by a temporal behavior that is strongly dependent on the position of the source on the Z. Evidence for an…
The winds of O-stars. II. The terminal velocities of stellar winds ofO-type stars.
Pauldrach, A. W. A.; Lamers, H. J. G. L. M.; Groenewegen, M. A. T.
The SEI method (Lamers et al., 1987) is used to obtain P Cygni profiles of the UV resonance lines of C IV, N V, and S IV and of the subordinate UV lines of N IV and C III observed in the spectra of 27 O-type stars. Theoretical profiles which include the turbulence effects agree well with the observations, and they can account for the deep absorpti…
The photodissociation of water in cometary atmospheres
Crovisier, J.
It is now known from laboratory and theoretical works that following water photodissociation, the OH radical is created in excited states of rotation or vibration. This fact was neglected in previous models of water photodissociation in cometary atmospheres. The goal of the present paper is to update these models. The water life time is not change…
Spectral classification of low-mass X-ray binary (LMXB) energy spectra with color-color diagrams.
Hasinger, G.; Truemper, J.; Schulz, N. S.
In this article we describe spectral variations of a large sample of low-mass X-ray binaries (LMXBs). The observations are done with the European X-ray Observatory EXOSAT. We decomposed the measured X-ray spectrum into three energy bands and plotted them into color-color and hardness-intensity diagrams. Correlations are compared with a few templat…
The X-ray flare and the quiescent emission from Algol as detected by EXOSAT.
Mewe, R.; van den Oord, G. H. J.
The Algol system was observed on August 18/19,1983 with different combinations of three instruments aboard EXOSAT: the low-energy channel multiplier array, the medium-energy proportional counters, and the transmission grating spectrometer. The X-ray flare observed on August 19 was analyzed and the decay phase was studied. It is shown that during t…
The X-ray ephemeris of Cygnus X-3.
van der Klis, M.; Bonnet-Bidaud, J. M.
A set of 17 measurements of the arrival time of the 4.8-hr period of the X-ray binary Cygnus X-3 over an interval of 2.3 yr are derived from Exosat data. These measurements are combined with previous data to study the period of Cygnus X-3 for the period 1970-1985. A cubic ephemeris with a 99.9 percent confidence fit to the data is presented with a…
Evaluation of cometary dust parameters from numerical simulations: comparison with an analytical approach and the role of anisotropic emissions.
Fulle, M.
A numerical method is developed which models cometary dust tails by means of sample grains. The orbital motion of the grains is rigorously computed, avoiding any Finson-Probstein hypersonic condition and dust shell geometry approximation. The model is applied to the dust tails of Comet Seki-Lines 1962III and Comet Kohoutek 1973XII. The results sho…
Rotational modulation and flares on RS Canum Venaticorum and BY Draconis stars. XI. Ultraviolet spectral images of AR Lacertae in September 1985.
Linsky, J. L.; Walter, F. M.; Neff, J. E. +1 more
High-resolution IUE SWP and LWP spectra of the bright eclipsing RS CVn system AR Lac, obtained during 40 h of continuous observations on September 18-19, 1985, are compiled and used to derive chromosphere images. The data and results are presented graphically and discussed in detail. The K 0 IV star is found to have a globally brighter trailing he…
The luminous quasar HS 1700+6416 and the shape of the "big bump" below 500 A.
Clavel, J.; Reimers, D.; Wamsteker, W. +5 more
In the course of the Hamburg quasar survey a bright (V = 16.1) high redshift (z = 2.72) quasar has been discovered. Follow-up optical high (0.4 A) and low (6 A) resolution spectrophotometry together with IUE observations are presented. With a luminosity at λ_rest_ = 1450 A, L_1450_ = 6 x 10^32^ erg s^-1^ Hz^-1^, HS1700+6416 is the second most lumi…
EXOSAT observations of the X-ray burst source 4U 1608-52.
van Paradijs, J.; Lewin, W. H. G.; Tan, J. +2 more
The results of an analysis of two Exosat observations (July 1984, May 1986) of the highly variable X-ray burst source 4U 1608-52 are presented. During both observations the persistent X-ray flux was low (quiescence), and the persistent X-ray spectrum could be well fitted with a power-law model, with approximately the same index, but a somewhat dif…