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Origin of the O^+^ pick-up ions in the heliosphere.
Geiss, J.; Mall, U.; Gloeckler, G.
The main sources for the ions in the interplanetary medium are the solar wind and the interstellar gas intruding into the heliosphere. Other sources, i.e. comets and planets can, however, contribute significantly locally. We present approximate expressions for deriving fluxes of pick-up ions originating from local neutral gas sources. Since the Io…
Hubble Space Telescope Fine Guidance Sensor Interferometric Observations of the Core of 30 Doradus
Lattanzi, M. G.; Bucciarelli, B.; Evans, I. N. +7 more
We present the results of the first high angular resolution observations taken with a Fine Guidance Sensor (FGS) aboard the Hubble Space Telescope (HST) of a star cluster embedded in very bright background. The strong and complex background around the R136 cluster in the 30 Dor nebula does not prevent the FGS from achieving performance close to it…
There is no ``cometopause'' at Comet Halley
Chaizy, P.; Reme, H.; Korth, A. +3 more
Immediately after the flybys at comet Halley by a fleet of spacecraft in 1986, Gringauz et al. (1986a) reported the detection by the Vega-2 spacecraft of a chemical and sharp plasma boundary, which they named the ``cometopause,'' at a distance of ~1.6×105 km from the nucleus. Gringauz and Verigin (1991) presented the ``cometopause'' as …
Generalized Spectral Model for 1--100 keV X-Ray Emission from Cygnus X-3 Based on EXOSAT Data
Singh, K. P.; Rao, A. R.; Chitnis, V. R. +1 more
The X-ray spectrum of the highly variable X-ray source, Cyg X-3, has so far defied a consistent explanation based on simple emission models. We have extracted two of the best data sets from the EXOSAT archives and performed a detailed spectral analysis for its 'high' and 'low' states. The analysis of the less frequently occurring 'low' state is pr…
Hysteresis in broad-line regions of active galactic nuclei.
van Groningen, E.; Wanders, I.; Perry, J. J.
The response of emission-line luminosities to changes in the observed continuum in active galaxies is commonly used for reverberation mapping (RM) of the emission-line region. The method assumes regularity in the continuum source and linearity in the line response to the continuum, and that the phase-space distribution of the line-emitting gas is …
A Far-Ultraviolet Atlas of Symbiotic Stars Observed with IUE. I. The SWP Range
Kafatos, M.; Michalitsianos, A. G.; Fahey, R. P. +1 more
This atlas contains sample spectra from the far-ultraviolet observations of 32 symbiotic stars obtained with the International Ultraviolet Explorer (IUE) satellite. In all, 394 low-resolution spectra from the short-wavelength primary (SWP) camera covering the range 1200-2000 A have been extracted from the IUE archive, calibrated, and measured. Abs…
Hubble Space Telescope Observations of Planetary Nebulae in the Magellanic Clouds. II. SMP 85, A Young Planetary
Dopita, Michael A.; Ford, Holland C.; Maran, Stephen P. +6 more
We have obtained Hubble Space Telescope Planetary Camera images in the [O III] λ5007 A emission line, and FOS UV spectrophotometry of the low-excitation planetary nebula SMP 85 in the Large Magellanic Cloud. By combining these results with existing optical spectrophotometry, absolute flux measurements, and dynamical and density information, we hav…
Determining hot star wind terminal velocities from low-resolution IUE data.
Prinja, R. K.
Empirical relations are provided which enable consistent determinations of wind terminal velocities for hot stars where only low-resolution IUE spectra are available. The calibrations are based on terminal velocities derived from the violet limit of `black' absorption troughs seen in high-resolution IUE spectra of saturated wind lines of hot stars…
The 1992/93 Eclipse of 31 Cygni
Eaton, Joel A.; Bell, Coretta
Extensive new ultraviolet and optical spectra of an atmospheric eclipse define the physical properties throughout the wind and chromosphere of 31 Cyg. These data require mass loss of approximately 3 x 10-8 solar masses/yr in a wind that may merge smoothly into the chromosphere. Considerations of how energy is injected into the wind, how…
Directivity of 100--500 keV Solar Flare Hard X-Ray Emission
Hurley, K.; Niel, M.; Li, P. +3 more
We have identified 28 solar flares simultaneously observed by a SIGNE detector aboard the Venera 13 and Venera 14 spacecraft and the Hard X-Ray Burst Spectrometer (HXRBS) aboard the Solar Maximum Mission (SMM), over a wide range of observing angles. Fourteen of them were also observed by the Gamma Ray Spectrometer (GRS) on SMM and were included in…