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Planetary Camera Observations of the Double Nucleus of M31
Holtzman, J. A.; Faber, S. M.; Ewald, S. P. +13 more
V- and I-band HST Planetary Camera images of the great spiral galaxy in Andromeda, M31, show that its inner nucleus consists of two components separated by 0.49". The outer isophotes of the nucleus at 1.4" < r < 3.0" are elongated, but are concentric with the M31 bulge. The nuclear component with the lower surface brightness, P2, is also coi…
Elemental abundances in normal late-B and HgMn stars from co-added IUE spectra. I. Iron-peak elements.
Dworetsky, M. M.; Smith, K. C.
The abundances of five iron-peak elements (chromium through nickel) in a sample of forty normal, superficially normal, and HgMn-type late-B stars are derived by spectrum-synthesis analysis of co-added high-resolution International Ultraviolet Explorer (IUE) spectra. Approximately solar abundances of these elements are obtained for the normal stars…
The Ulysses neutral gas experiment: Determination of the velocity and temperature of the interstellar neutral helium
Rosenbauer, H.; Witte, M.; Banaszkiewicz, M. +1 more
A new technique to directly detect low energy neutral helium has been developed and successfully used in space for the first time. It makes possible the in-situ measurement of the local angular distribution of the flow of interstellar neutral helium in the inner heliosphere. Based on the transformation of a velocity distribution, using Liouville's…
SN 1992A: Ultraviolet and Optical Studies Based on HST, IUE, and CTIO Observations
Suntzeff, N. B.; Fransson, Claes; Challis, Peter M. +18 more
The Type Ia supernova SN 1992A in the 50 galaxy NGC 1380 was observed as a target of opportunity by the International Ultraviolet Explorer (IUE) and with great alacrity by the Hubble Space Telescope (HST). Here we present the HST and lUE spectra and photometry that we obtained, as well as optical spectra obtained at the Cerro Tololo Inter-American…
X-Ray Variability of Active Galactic Nuclei: A Universal Power Spectrum with Luminosity-dependent Amplitude
Papadakis, I.; Lawrence, A.
We present power-law model fits to the power spectra of 12 high- quality "long look" observations of AGNs from the EXOSAT data base. The AGNs concerned differ in X-ray luminosity L_x_, over a range 10^4^. The results are consistent with all objects having a power spectrum index equal to the mean value α = 1.55. There is no correlation with L_x_, s…
Five populations of interplanetary meteoroids
Divine, Neil
A description of the interplanetary meteoroid environment is proposed in terms of distinct populations, each of which has separable distributions in particle mass and in orbital inclination, eccentricity, and perihelion distance. This treatment leads to expressions for particle concentration and flux which explicitly incorporate both Keplerian dyn…
High Resolution Imaging of Galaxy Cores
Boksenberg, A.; Barbieri, C.; Weigelt, G. +17 more
Surface photometry data obtained with the Faint Object Camera of the Hubble Space Telescope in the cores of ten galaxies is presented. The major results are: (i) none of the galaxies show truly "isothermal" cores, (ii) galaxies with nuclear activity show very similar light profiles, (iii) all objects show central mass densities > 10^3^M_sun_ pc…
On the nature of rapid X-ray variability in active galactic nuclei.
McHardy, I. M.; Lehto, H. J.; Green, A. R.
We systematically analyse all (110) EXOSAT AGN medium-energy light curves of length greater than 20 ks to search for and quantify their flux variability. We also perform extensive simulations to quantify the selection effects (such as the source brightness or the length of observation) that might prevent the detection of variability. We quantify v…
Ulysses observations of a recurrent high speed solar wind stream and the heliomagnetic streamer belt
McComas, D. J.; Goldstein, B. E.; Bame, S. J. +4 more
Near-ecliptic solar wind observations by Ulysses on its way to the polar regions of the Sun, compared with those from IMP 8 at 1 AU, showed that high-speed streams decay and broaden with heliocentric distance from IMP 8 to Ulysses, as expected. In July 1992 while travelling south at ∼13°S and 5.3 AU, Ulysses encountered a recurrent high-speed stre…
Perpendicular transport in 1- and 2-dimensional shock simulations
Giacalone, J.; Jokipii, J. R.; Kota, J.
We consider the foundations of 1- and 2-dimensional shock simulations in which the physical quantities are independent of a coordinate which is not parallel to the magnetic field. We show analytically that in such simulations the ions are effectively tied to the convected magnetic lines of force because of the presence of an ignorable spatial coor…