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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…
The Transient 42 Second X-Ray Pulsar EXO 2030+375. II. The Luminosity Dependence of the Pulse Profile
Stella, L.; Parmar, A. N.; White, N. E.
During an outburst from the transient, 42 s, X-ray pulsar EXO 2030+375, marked luminosity-dependent changes in pulsar profile were observed. At high luminosities the pulse profile consisted of a smooth asymmetric main pulse separated by about 180 deg in phase from a small interpulse. As the luminosity decreased by a factor of about 100, the relati…
Velocity space diffusion of pickup ions from the water group at Comet Halley
Coates, A. J.; Glassmeier, K. -H.; Wilken, B. +2 more
We have studied the diffusion in velocity space of cometary ions using the distributions of ions measured by the implanted ion spectrometer on Giotto during the inbound pass. The measurements were transformed into a frame comoving with the solar wind and oriented with the magnetic field. The observations show the evolution of the pitch angle distr…
Pre--Main-Sequence Disk Accretion in Z Canis Majoris
Kenyon, S. J.; Stauffer, J. R.; Edwards, S. +4 more
It is suggested that the pre-main-sequence object Z CMa is a luminous accretion disk, similar in many respects to the FU Orionis variables. Z CMa shows the broad, doubled optical absorption lines expected from a rapidly rotating accretion disk. The first overtone CO absorption detected in Z CMa is blue-shifted, suggesting line formation in a disk …
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…
Spin modulated X-ray emission from intermediate polars.
Watson, M. G.; Norton, A. J.
This paper describes a comparative study of all the intermediate polars observed by Exosat. The X-ray pulse profiles of each source are presented, and it is shown that, in all cases, the modulation can be described in terms of an increasing depth with decreasing energy. By considering the pulse phase-resolved spectra, it is shown that the modulati…
Coronal Activity in F-, G-, and K-Type Stars. III. The Coronal Differential Emission Measure Distribution of Capella, sigma 2 Coronae Borealis, and Procyon
Mewe, R.; Schrijver, C. J.; Lemen, J. R. +1 more
EXOSAT soft X-ray spectra of three binary systems of cool stars are analyzed: Capella (G6 III + F9 III), Sigma-squared CrB (F8 V + G1 V), and Procyon (F5 IV-V + DF). The EXOSAT transmission grating spectrometer permits the study of individual spectral lines and line complexes between 10 and 200 A with approximately 3 A resolution. First it is demo…
Variable X-ray absorption in NGC 4151.
Warwick, R. S.; Yaqoob, T.; Pounds, K. A.
The Seyfert galaxy NGC 4151 was monitored over 20 times by EXOSAT in the period 1983 July-1986 March. The very soft spectral component detected by the EXOSAT low-energy telescope, which may be thermal emission from the narrow-line region of NGC 4151, remained constant over the observing period. In contrast, the medium-energy X-ray continuum emanat…
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…