Search Publications
A comparison of interplanetary coronal mass ejections at ULYSSES with YOHKOH soft X-ray coronal events.
Forsyth, R. J.; Burkepile, J. T.; Phillips, J. L. +5 more
Coronal Mass Ejections (CMEs) observed at several AU by the Ulysses spacecraft are mapped radially back to the Sun and compared with Yohkoh Soft X-ray Telescope (SXT) images of the corona in an effort to identify correlated events. Correlations between the observations were difficult to make during the ecliptic phase of the Ulysses mission when th…
Azimuthal structures in the wind and chromosphere of the Herbig AE star AB Aurigae. Results from the MUSICOS 1992 campaign.
Talavera, A.; Donati, J. -F.; Semel, M. +19 more
The observations of the MUSICOS 1992 campaign concerned three scientific programs, among which was the study of azimuthal structures in the wind and chromosphere of the pre-main sequence Herbig Ae star AB Aur. The He I 5876A line of AB Aur, which is formed in the expanding chromosphere of this star, most probably in the innermost parts of its wind…
HST/GHRS Observations of the beta Pictoris System. II. Exploring the Potential for Tracking Comet-like Objects Orbiting the Star
Hubeny, Ivan; Heap, Sara R.
We present a systematic study of the transient absorption features observed in the spectra of β Pictoris. We calculate detailed synthetic spectra of a star, which is partially obscured by a permanent circumstellar disk and by an absorbing body of a given size, position, radial velocity with respect to the star, and total column density. We show th…
Discovery of Photospheric Helium in the Ultra-Massive DA White Dwarf GD 50
Bowyer, Stuart; Vennes, Stephane; Dupuis, Jean
Extreme-ultraviolet (EUV) spectroscopy of the hot, hydrogen-rich white dwarf GD 50 reveals an unusual photospheric mixture of hydrogen and helium. This hot DA white dwarf is also remarkable for its mass (~1.2 M⊙) near the Chandrasekhar limit. The spectra obtained with the Extreme-Ultraviolet Explorer (EUVE) show a prominent He II resonance line se…
Radial velocities and axial rotation for a sample of chemically peculiar stars.
Morrell, N.; Levato, H.; Grosso, M. +2 more
As part of a systematic project we have determined radial velocities and projected rotational velocities for a sample of 186 chemically peculiar stars which have been observed by the Hipparcos' satellite. The purpose is to provide necessary data to study the space velocities of peculiar stars.
Hubble Space Telescope Spectroscopic Observations of the Ejecta of SN 1987A at 2000 Days
Filippenko, Alexei V.; Fransson, Claes; Challis, Peter M. +6 more
We have used the Faint Object Spectrograph on the Hubble Space Telescope (HST) to observe the spectra of SN 1987A over the wavelength range 2000-8000 A on dates 1862 and 2210 days after the supernova outburst. Even these preCOSTAR observations avoid much of the contamination from the bright stars nearby and provide a very useful set of line streng…
A Supergiant-Dominated Starburst in the Nucleus of NGC 4569
Keel, William C.
The Virgo spiral NGC 4569 has a very compact optical nucleus whose spectrum is highly composite, which strong Balmer absorption indicating that A stars dominate the optical light. Recent HST imaging shows that the nucleus is extremely compact in the mid-ultraviolet, so that either there must be a central AGN or an extraordinarily luminous and comp…
The Broadband Energy Distribution of the Misaligned Gamma-Ray Blazar PKS 0521-365
Maraschi, L.; Ghisellini, G.; Pian, E. +4 more
Simultaneous UV and X-ray observations of the blazar PKS 0521-365 are combined with radio, IR, optical, and y-ray data taken at different epochs to study the overall emission from 10 to 1023 Hz. The flux distribution declines from the IR to the UV range (alpha0pt uv = 1.4 + 0.1), but hardens at higher frequencies. The remarkably flat X-…
Abundance and Isotopic Anomalies of Thallium in the Atmosphere of the HgMn Star χ LUPI
Johansson, Sveneric; Wahlgren, Glenn M.; Proffitt, Charles R. +3 more
We announce the detection of two fully resolved hyperfine components of the intercombination line of Tl II (Z = 81) at 1908.6 Å in the ultraviolet spectrum of the sharp-lined, nonmagnetic, chemically peculiar star χ Lupi (B9.5pHgMn + A2 Vm). The wavelengths and profiles of these absorption lines strongly suggest that they arise from the heaviest i…
Hubble Space Telescope Time-resolved Ultraviolet Spectroscopy of ST Leonis Minoris and UZ Fornacis: Resolving the Accretion Stream
Schmidt, Gary D.; Stockman, H. S.
Time-resolved, low-resolution ultraviolet spectroscopy of the magnetic cataclysmic variables ST LMi and UZ For was obtained with the Hubble Space Telescope during periods near eclipse and self-eclipse egress, respectively. The UZ For data indicate three eclipsing components: the white dwarf; a hot, presumably photo spheric emission region on the w…