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Simulation of the Morphology of the Jovian UV North Aurora Observed with the Hubble Space Telescope
Waite, J. H.; Grodent, D.; Gladstone, G. R. +2 more
A model simulating Earth views of UV auroral arcs and diffuse emissions in the Jovian north polar region is described. It assumes a Chapman profile of vertical brightness distribution and various horizontal structures. Simple geometric cases are described to illustrate the dependence on the altitude, atmospheric scale height, and central meridian …
Determination of the Formation Temperature of Si IV in the Solar Transition Region
Wilhelm, K.; Schühle, U.; Lemaire, P. +4 more
Using spectra obtained with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer flown on the Solar and Heliospheric Observatory spacecraft, we deduce the temperature of formation of the Si IV ion in the solar transition region from the Si IV ultraviolet spectral line intensity ratio, 3p 2P3/2-3d …
Subarcsec structures in the double nucleus of NGC6240 disclosed with HST at 370, 430 and 500 NM
Barbieri, C.; Komossa, S.; Rafanelli, P. +4 more
We present an analysis of three medium band width (FWHM ~ 400 - 450 Angstroms) images of the nuclear region of NGC6240 taken with the pre-COSTAR Faint Object Camera (FOC) on board of the Hubble Space Telescope. The first filter band comprises the [OII]lambda 3727 doublet, the second measures the blue continuum around 4400 { Angstroms} and the thir…
Testing the X-ray variability of active galactic nuclei with the non-linear prediction method
Czerny, Bozena; Lehto, Harry J.
The analysis of eight EXOSAT X-ray light curves of six active galactic nuclei by non-linear prediction methods indicates that the observed variability is truly stochastic and is not caused by deterministic chaos. This result favours X-ray emission models with multiple centres of production of hot, possibly relativistic, electrons.
Ultraviolet Spectroscopy of Hot Compact Stars.
Rauch, T.; Werner, K.; Dreizler, S. +4 more
Redshift survey of gravitational arclets in Abell 2390.
Soucail, G.; Bezecourt, J.
In this paper, we present new determinations of redshifts on a sample of gravitational arclets identified in the cluster of galaxies Abell 2390. The arclets candidates were selected from their elongated morphology as seen in recent deep HST images of the cluster. The spectra display various features, and the redshifts of the background objects ran…
HD 111786: a spectroscopic binary λ Boo star.
Gerbaldi, M.; Faraggiana, R.; Burnage, R.
HD 111786 = HR 4881 is one of the most interesting λ Boo stars; in fact it is one of the few stars of this class which shows narrow features that can be interpreted as remnants of the circumstellar matter from which star was formed. On the basis of optical observations and inspection of IUE spectra, we demonstrate that HD 111786 is, as a matter of…
An estimate of the solar background irradiance power spectrum.
Rabello-Soares, M. C.; Roca Cortes, T.; Jimenez, A. +2 more
Knowledge of the solar irradiance background is of great importance to solar and stellar physics. In particular, its contribution to the solar oscillations power spectrum is highly relevant as it represents the ultimate limit to the sensitivity of solar oscillations' observations. An analysis of the power spectra of the solar photometric data comi…
The Amount of CH Produced during CH+ Synthesis in Interstellar Clouds
Welty, D. E.; Federman, S. R.; Cardelli, Jason A.
A particularly useful constraint for models of CH+ formation in interstellar clouds is knowledge of the amount of CH associated with CH+ synthesis. For lines of sight with no detectable CN absorption, this column of CH can be inferred through a combined analysis of C I excitation and simplified chemical models. The approach i…
Doppler imaging of stellar surface structure. III. The X-ray source HD 116544 = IN Virginis.
Strassmeier, K. G.
We present the first Doppler image of the EXOSAT X-ray source EXO 1321.8-0203, recently identified to be a chromospherically active star exhibiting periodic light variations and consequently named INVirginis. Our high-resolution spectra show INVirginis to be a single-lined spectroscopic binary with an orbital period of 8.2 days, very strong CaII e…