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Coronal Mass Ejections at High Heliographic Latitudes: ULYSSES
Balogh, A.; McComas, D. J.; Bame, S. J. +3 more
Nine coronal mass ejections (CMEs) have been detected in the solar wind by the Ulysses plasma experiment between 31° and 61° South. One of these events, which was also a magnetic cloud, was directly associated with an event observed by the soft X-ray telescope on Yohkoh in which large magnetic loops formed in the solar corona directly beneath Ulys…
Atomic Physics with the Goddard High-Resolution Spectrograph on the Hubble Space Telescope. I. Oscillator Strengths for Neutral Sulfur
Federman, S. R.; Cardelli, Jason A.
Interstellar spectra toward ζ Oph acquired with the Goddard High-Resolution Spectrograph were used to obtain oscillator strengths for approximately two dozen S I lines. This analysis was possible because precisely determined experimental oscillator strengths are available for several multiplets, including one with a weak interstellar line. The sel…
Construction of the intermediate HIPPARCOS astrometric catalogue
Lattanzi, M. G.; Lindegren, L.; Mignard, F. +15 more
The data analysis methods for the determination of the astrometric parameters from observations by the Hipparcos satellite as used in FAST and NDAC consortia for the construction of intermediate 18-month and 30-month solutions are presented. The quality of the results depends upon calibrations of the instrumental parameters, examples of which are …
Optical Structure and Polarization of the Western Hot SPOT of Pictor A
Crane, P.; Mackay, C. D.; Thomson, R. C.
HST images of the western hot spot of the nearby FR II radio galaxy Pictor A resolve the hot spot into an amorphous region of highly polarized wisps. The high polarization (≳50%) indicates that the optical emission is synchrotron radiation and that the magnetic field structure has been well resolved. The magnetic field is oriented nearly perpendic…
On the relative luminosities of the stars in the Wolf-Rayet binary V444 Cygni.
Koenigsberger, G.; Cherepashchuk, A. M.; Moffat, A. F. J. +1 more
A new spectroscopic estimate of the luminosity ratio q=L_WR_/L_O6_ is obtained from the dilution of the absorption lines of the O6V-III component in the WR eclipsing binary V444 Cygni (WN5+O6). We find q=0.60+/-0.06 for the range λλ4000-6000A and q=0.56+/-0.13 from IUE spectra. This clearly indicates that the light of the O6 dominates the combined…
High-Resolution Ultraviolet Spectroscopy of Jupiter's Aurora with the Hubble Space Telescope
Caldwell, J. J.; Fox, J. L.; Kim, Y. H.
In 1993 June and July, we obtained 18 spectra of Jupiter's aurora in the wavelength range 1586-1620 Å using the Goddard High Resolution Spectrograph on board the Hubble Space Telescope (HST). The field of view for each observation was 2" × 2". There were 14 spectra of the northern and four spectra of the southern auroral ovals. The spectra are dom…
The ultraviolet properties of cool material ejected by hydrogen-deficient stars.
Jeffery, C. S.
Carbon-rich H-deficient stars which shed dusty material in the line-of-sight exhibit RCrB-like optical variations. The UV extinction toward several such objects differs significantly from the average interstellar extinction law; these data have been re-examined. The observed peak in extinction at 4.1µm^-1^(=240nm) has previously been explain…
HST-GHRS observations of Sirius A. III. Detection of a stellar wind from Sirius A
Ferlet, R.; Vidal-Madjar, A.; Lallement, R. +2 more
Observations of Sirius A with the GHRS instrument on board the Hubble Space Telescope revealed the presence of absorption features in the blue wings of the strong MgII and Hi resonance lines in the velocity range from -20km/s to -80km/s. These features are probably due to the stellar wind of Sirius rather than to blends of photospheric lines becau…
Terminal Velocities of Wolf-Rayet Star Winds from Low Resolution IUE Spectra
Niedzielski, A.; Rochowicz, K.
Attracted by the simplicity of the recently published by Prinja (1994) method of determination of terminal wind velocities in hot stars from low resolution IUE spectra we investigate its application to WR stars. With a large sample of low resolution IUE spectra of WR stars we found even simpler, that is linear instead of square, empirical relation…
The stellar wind of an O8.5I(f) star in M31. A determination of mass loss rate and metallicity.
Lennon, D. J.; Bianchi, L.; Pauldrach, A. W. A. +4 more
We rediscuss the UV spectrum of OB78#231, an O8.5I(f) star in the Andromeda galaxy M31, which has been obtained with the Faint Object Spectrograph on the Hubble Space Telescope by Hutchings et al.. The spectrum has been reextracted with better knowledge of background, calibration, and scattered light. The empirical analysis of the stellar wind lin…