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Energy Release and Dissipation during Giant Solar Flares
Hurley, K.; Sommer, M.; Boer, M. +3 more
The Solar X-Ray/Cosmic Gamma-Ray Burst Experiment aboard Ulysses has observed 11 solar hard X-ray flares with effective peak counting rates greater than 4 × 105 counts s-1. We have estimated the energy dissipated during these "giant" flares (GOES class > X12). The flare on 1991 June 1, probably the largest flare of the pre…
Ultraviolet Spectropolarimetry of High-Redshift Quasars with the Hubble Space Telescope
Impey, C. D.; Malkan, Matthew A.; Webb, Wayne +1 more
Ultraviolet spectropolarimetry of three bright high-redshift low- polarization quasars (LPQs) was obtained with the Faint Object Spectrograph of the Hubble Space Telescope. Two of the quasars, PG 1634+706 and PG 2302+029, had polarizations p ~ 0.5%-1.0% throughout the ultraviolet, and showed no significant variation of polarization amplitude or po…
Faint Object Camera Imaging and Spectroscopy of NGC 4151
Boksenberg, A.; Barbieri, C.; Weigelt, G. +17 more
We describe ultraviolet and optical imaging and spectroscopy within the central few arcseconds of the Seyfert galaxy NGC 4151, obtained with the Faint Object Camera on the Hubble Space Telescope. A narrowband image including [O III] λ5007 shows a bright nucleus centered on a complex biconical structure having apparent opening angle ~65^deg^ and ax…
Comparative study of the asteroidal motion in the 3:2 and 2:1 resonances with Jupiter. I. Planar model.
Ferraz-Mello, S.; Michtchenko, T. A.
The long-period behavior of the asteroids in the 3:2 and 2:1 resonances with Jupiter is investigated by integrating numerically the equations of motion of the planar three-body system. The results of the numerical integration procedure were submitted to a low-pass filtering and the decimation parameter was chosen in accordance with the filter. The…
Metal abundances in subdwarf O stars.
Husfeld, D.; Bauer, F.
We describe a non-LTE analysis of seven subdwarf O stars and four central stars of planetary nebulae. The analysis yields metal abundances (or upper limits to these) of C, N, O, Mg, Al, and Si for most of these stars. Also effective temperature, surface gravity and helium abundance were determined for those programme stars for which no reliable es…
Solar Wind Corotating Stream Interaction Regions Out of the Ecliptic Plane: ULYSSES
McComas, D. J.; Goldstein, B. E.; Bame, S. J. +4 more
Ulysses plasma observations reveal that the forward shocks that commonly bound the leading edges of corotating interaction regions (CIRs) beyond ∼2 AU from the Sun at low heliographic latitudes nearly disappeared at a latitude of S26°. On the other hand, the reverse shocks that commonly bound the trailing edges of the CIRs were observed regularly …
Ultraluminous Infrared Galaxies and the Radio-optical Correlation for Quasars
Lonsdale, Carol J.; Smith, Harding E.; Lonsdale, Colin J.
Through analysis of available optical spectrophotometric data and radio flux density measurements in the literature, it is demonstrated that a good correlation exists between the radio power and bolometric luminosity of the optically-selected QSOs in the Bright Quasar Sample (BQS) of Schmidt & Green (1983). This correlation, noted previously b…
Lithium Abundances in Strong Lithium K Giant Stars: LTE and Non-LTE Analyses
de La Reza, Ramiro; da Silva, Licio
Detailed non-Local Thermodynamic Equilibrium (non-LTE) and LTE analyses are made of two very strong Li K giants, HD 19745 and HD 39853, and of the strong Li K giant HD 787. The stronger star HD 19745 has recently been discovered to show very strong Li. These analyses are based on the observations done at European Southern Observatory (ESO) of the …
Physics and chemistry of ions in the pile-up region of comet P/Halley.
Altwegg, K.; Balsiger, H.; Geiss, J. +1 more
Measurements by the mass spectrometers onboard Giotto during the flyby at comet P/Halley showed a steep increase in the ion density outside the diamagnetic cavity at a distance of about 8000km from the nucleus (Balsiger et al. 1986a; Krankowsky et al. 1986). The maximum ion density was observed at a distance of 12000km from the nucleus rather than…
Multifrequency Spectra of EXOSAT Blazars
Ghosh, K. K.; Soundararajaperumal, S.
Blazars have been divided into two groups: radio-selected blazars (RBLs) and X-ray-selected blazars (XBLs). Results of the X-ray spectral analysis of 28 such blazars which were observed with EXOSAT are presented in this paper, and in four these are new results which were not published earlier. X-ray results suggest that XBLs are steep-spectrum sou…