Search Publications
Properties and Nature of Be Stars. 14. Is KX And a Strongly Interacting Binary?
Harmanec, P.; Hadrava, P.; Koubsky, P. +5 more
This paper summarizes and adds to the observational knowledge of KX And, a peculiar emission-line object. A formal orbital solution, based on new Ondrejov and all previously published radial velocities of the metallic shell lines in the optical region has led to an improved ephemeris. Radial velocities of various lines measured in the IUE spectra …
EXOSAT measurements of the pulse period of VELA X-1.
Raubenheimer, B. C.; Oegelman, H.
Seven new pulse period determinations of Vela X-1 have been made using the existing Exosat data. The measurements span one year and partly fill in the 3.2 yr gap between Tenma and Ginga measurements. The new results show that one pulse period of Vela X-1 continued with an epoch or near-constant period starting in 1981 and lasting up to at least Ma…
An Evolving Relativistic Jet Model for the BL Lacertae Object Markarian 421
Kondo, Y.; Urry, C. M.; Hutter, D. J. +2 more
Coordinated observations of the nearby BL Lacertae object Mrk 421 obtained during 1980 May, 1984 January, and 1984 March are described. These observations give a time-frozen picture of the continuous spectrum of Mrk 421 at X-ray, ultraviolet, optical and radio wavelengths. The observed spectra have been fitted to an inhomogeneous relativistic jet …
First observations of a corona of a cool bright giant with height resolution.
Reimers, D.; Baade, R.; Schroeder, K. -P. +1 more
Two time series of observations of the corona of HR 6902, as seen in the CIV and SiIV absorption lines during the 1988 and 1989 eclipses, are used to examine the density distribution of the expanding corona as a function of height. It is shown that the scaling laws for thermally driven winds predict coronal densities and mass-loss rates too low by…
Giotto IMS measurements of the production rate of hydrogen cyanide in the coma of comet Halley.
Schwenn, R.; Balsiger, H.; Geiss, J. +7 more
The ion composition measurements in the ionosphere of comet Halley by the ion mass spectrometer (IMS) experiment on the Giotto spacecraft are used to estimate the relative abundance of HCN. From a comparison of the normalized number density of ions with mass-to-charge (M/q) ratio of 28 AMU/e with steady-state photochemical models, it can be determ…
A New Powerful Test for Periodic Pulsed Emission of High-Energy Photons
Swanepoel, J. W. H.; de Beer, C. F.
A novel stastistical test devised for detecting periodic pulsations in a series of photon arrival times is found to perform powerfully in the detection of multiple, narrow peaked light curve shapes against a uniform background, especially if the light curve has multiple peaks. The statistical test has been applied to observations of the first 1350…
The UV spectrum of the WC 11 star CPD -56 8032.
Nandy, K.; Kameswara Rao, N.; Giridhar, S.
UV observations of the WC 11 central star of the compact planetary nebula CPD -56 deg 8032 show that the continuum flux is variable. This variability appears to be caused by a change in the circumstellar extinction properties. The UV energy distribution can be fitted with helium star models with T(eff) about 25000 K, after correcting for two types…
Hot Degenerates in the MCT Survey. I. MCT 0130-1937, a New, Color-selected PG 1159 Object
Kepler, S. O.; Fontaine, G.; Wesemael, F. +4 more
In the course of a survey for high-latitude, UV excess objects in the Southern Hemisphere, a new white dwarf star belonging to the PG 1159 spectroscopic class was discovered. A variety of spectroscopic observations show this object to be similar to the prototype PG 1159 - 035 in exhibiting He II, C IV, and O VI features in its optical spectrum, as…
X-ray spectra of three BL Lac objects.
Maccagni, D.; Garilli, B.
We present the results of the analysis of twin EXOSAT observations of three BL Lac objects, namely PKS 0521-365, PKS 0548-322, and I Zw 186. The energy spectra between 0.02 and ~ 7 keV can generally be described by power laws with a low energy cut off due to absorption by hydrogen in our galaxy. However, while PKS 0521-365 has a spectrum with an e…
The IUE spectrum of the Wolf-Rayet system HD 193077.
Koenigsberger, G.
The results of a detailed line-identification study of the IUE(1100-1900 A) spectrum of the Wolf-Rayet star HD 193077 (WR 138) is presented. The emission line spectrum is shown to be dominated by Fe V+Fe VI lines below 1500 A. The interstellar-line spectrum contains a large variety of atomic and ionic species, ranging from C I to Si IV and C IV, a…