Search Publications
The Ultraviolet to Infrared Energy Distribution of the BL Lacertae Object PKS 0422+00 at Two Different Brightness Levels
Maraschi, L.; Tanzi, E. G.; Bouchet, P. +2 more
The BL Lacertae object PKS 0422+00 was observed with IUE (International Ultraviolet Explorer) on 1987 August 31-September 1, when the visual magnitude of the object was V = 16.2, and again ~ 4 months later (1988 Jan 10) during an active state (V = 15.6). Quasi-simultaneous optical to infrared observations allow deriving a detailed spectral flux di…
A comparative study of the discrete and cross correlation techniques : an application to the NGC 5548 IUE light-curve.
Clavel, J.; Rodriguez-Pascual, P. M.; Santos-Lleo, M.
Over the past few years, cross-correlation techniques have become of increasing importance in the context of active galactic nuclei (AGN) variability studies. Inference of time delays in the response of the emission line intensities with changes in the ionizing continuum flux have the potential to yield the length scale of the broad line emitting …
Activity in late-type stars. IV. The 1980 August 20 flare on proxima Centauri revisited.
Byrne, P. B.; McKay, D.
This paper presents a reanalysis of simultaneous ultraviolet and soft X-ray observations of a flare on the dMe star, Proxima Centauri. Using an emission measure analysis, as well as density sensitive line ratios, the electron density and the total emitting volume of the flare plasma which is at midtransition region temperatures are derived. These,…
The EXOSAT view of the north and east Cygnus loop.
Ballet, J.; Rothenflug, R.
EXOSAT images of the northeast third of the Cygnus Loop are presented. The brightest parts are analyzed and the different filters on the CMA are used to put constraints on the temperature. This is especially valuable for the warm gas, for which temperatures as low as 1.4 x 10 to the 6th K in the east are estimated. The spectra obtained with EXOSAT…
Ultraviolet spectra of a large sample of quasars. I. Data and data reduction.
Gondhalekar, P. M.
Ultraviolet spectrophotometric data on all quasars (Z_e_ > 0.1) obtained with IUE from 1978 to the end of 1986 have been retrieved from IUE archive and re-extracted directly from the photometrically corrected images. A spectrum extraction procedure was used to maximize the signal-to-noise ratio and discriminate against spurious events outside t…
X-ray and optical observations of LDS 587.
Schmitt, J. H. M. M.; Pasquini, L.; Harnden, F. R., Jr. +2 more
During an Exosat observation of the RS CVn star HD 155555 (LDS 587 A) a serendipitous X-ray source (EXO 171224-6653.9) was discovered. This paper presents an analysis of the Exosat and Einstein Observatory (HEAO 2) X-ray observations as well as optical spectra of the serendipitous X-ray source; the X-ray properties of HD 155555 are also discussed.…
Time-dependent study of magnetic fields in comets giacobini-zinner and halley
Neubauer, F. M.; Huebner, W. F.; Slavin, J. A. +4 more
Stationary MHD models are used to analyze the data of magnetic field measurements in comets Giacobini-Zinner and Halley. The contributions of the draping, of changes in the IMF, and of turbulence are separated and extended patches of unidirectional field regions are identified. A time-dependent MHD simulation of the nonstationary flow following a …
Comparison of Einstein and EXOSAT Observations of SS 433
Band, David L.
Observations with the Einstein telescope which show SS 433 to be a flaring X-ray source with a variable power-law spectrum are compared to Exosat observations which show a relatively quiescent X-ray spectrum with a prominent blueshifted iron line consistent with thermal emission in the jets. Models to explain the differences between the two studie…
Chromospherically Active Stars. VI. HD 136901 = UV CrB: A Massive Ellipsoidal K Giant Single-Lined Spectroscopic Binary
Kirkpatrick, J. Davy; Fekel, Francis C.; Strassmeier, Klaus G. +1 more
The variable star HD 136901 = UV CrB is a chromospherically active K2 III single-lined spectroscopic binary with an orbital period of 18.665 days. It has modest-strength Ca H and K emission and UV features, while H-alpha is a strong absorption feature containing little or no emission. The inclination of the system is 53 + or - 12 deg. The v sin i …
The IUE spectral atlas of two normal B stars : pi Ceti and nu Capricorni (125-198 nm).
Lanz, T.; Borsenberger, J.; Artu, M. -C.
The ultraviolet spectra of two main-sequence B stars, Pi Cet (HD 17081) and Nu Capricorni (HD 193432) recorded by the IUE satellite have been used to elaborate a reference atlas, with line identification, in the low wavelength range 125-198 nm. To obtain realistic identifications and to select the dominant contributors in blends, a synthetic calcu…