Search Publications
Tentative confirmation of an aurora on Uranus
Owen, T.; Caldwell, J.; Encrenaz, Th. +2 more
There have been three recent reports of the detection of Lyman-alpha radiation (due to atomic hydrogen, H, at wavelength 1,216 A) from Uranus by means of the International Ultraviolet Explorer (IUE) satellite. The interpretations of these results differ. Two reports conclude that there is a strong aurora on Uranus, but the third concludes that the…
The relationship between soft X-rays and the 1640 A feature fluxes inlate-type stars.
Gonzalez-Riestra, R.; Rego, M.; Fernandez-Figueroa, M. J.
The relationship between the soft X-ray flux and the wavelength 1640 feature in a sample of late-type stars is studied. It is assumed that all the observed feature intensity comes from the helium line and that only the fraction of the He II line due to recombination is directly related to the X-ray flux. A close correlation is found between both f…
Quasi-simultaneous optical and UV observations of OJ 287 during an active period in 1983.
Maraschi, L.; Tanzi, E. G.; Falomo, R. +1 more
Far UV spectra (1200 - 3000 Å) of OJ 287 were taken with IUE on Feb. 15th, 1983. Optical spectrophotometry (4500 - 7800 Å) was obtained three days later with the 1.8 m telescope of the Asiago Observatory. The source was in an intermediate state, mV ≅ 14, between quiescence and the maximum reported in January (mV ≅ 13). A powe…
Mass loss in HR 1040 (AO Ia) : analysis of MG IILambda 2802 and Hα.
Kunasz, P. B.; Morrison, N. D.; Spressart, B.
It is pointed out that International Ultraviolet Explorer (IUE) data for several early A type supergiants are now available to complement the ground-based spectroscopic data available for these bright stars. An examination of the resonance doublet of Mg II in the A type supergiants reveals that HR 1040 (HD 21389) is the only star in the observatio…
IUE observations of the low-excitation planetary nebula Tc-1.
Feibelman, W. A.
Ultraviolet observations of Tc-1 confirm that the object is a low excitation planetary nebula with a central star of type O7. The nebular spectrum has few emission lines and the P Cygni character of the C IV line remains uncertain. A radial velocity of -95 km/s is found from the semiforbidden C III wavelength 1909 line, and an extinction of 0.22 m…
High rotational velocity of a region around the primary of Algol.
Molaro, P.; Cugier, H.
An analysis of the IUE spectra of Algol near λ2800 Å is performed. For this purpose the observations are compared with the calculated synthetic spectra. Significant differences are found. Near Mg II resonance lines, the observed spectra are situated below the calculated ones at the wavelength range from λ2790 Å to λ2807 Å. This local depression is…
An attempt to determine stellar Lyman-Alpha emission-line fluxes for F stars with different metal abundances.
Bohm-Vitense, E.; Woods, J.
We have studied stellar Lyα fluxes for F stars of different metal abundances which are presumably older the more metal deficient they are. We describe the correction procedure for the geocoronal emission and our estimate of the correction for interstellar absorption. We find stronger than average Lyα emission for the Hyades stars and for the two c…
IUE observations of the nucleus of the galactic globular cluster NGC 2808.
Caloi, V.; Castellani, V.
The UV spectrum of the nucleus of the galactic globular cluster NGC 2808 shows two distinct components: a point-like one, probably a supra BHB star of about 40,000K in the phase of rapid crossing of the HR diagram from the red giant tip, and a diffuse one, interpreted as a clump of blue HB stars. The contribution of these HB stars produces a clust…
X-ray observations of bright galactic bulge sources in the vicinity of GX 5-1.
van der Klis, M.; Rappaport, S.
Results are presented for 44 d of pointed COS-B X-ray observations of the galactic center region around GX5-1. It is found that GX5-1 exhibits relatively rapid (≡103 s) intensity transitions as well as flaring events with a typical time scale of ≡104 s. Neither GX5-1, GX3+1 nor GX9+1 shows evidence of periodic intensity modul…
A method to improve the visibility of time-variable gamma-ray sources in structured background
Mayer-Hasselwander, H. A.; Oezel, M. E.
For the investigation of time variable gamma-ray sources (e.g. pulsars) embedded in a spatially structured background emission, the spatial selection of those gamma-ray events which are probable to increase the observed signal is not a trivial task. A method is presented which allows for the optimum event selection without introducing any statisti…