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Ultraviolet Emission from the Liner Nucleus of NGC 6500
Filippenko, Alexei V.; Ho, Luis C.; Shields, Joseph C. +3 more
As a step towards clarifying the ionization mechanism of LINERs, we have used the Hubble Space Telescope Faint Object Spectrograph to obtain an ultraviolet spectrum of the nucleus of NGC 6500. This is the first time that such a spectrum has been taken of a "LINER 2" nucleus-that is, a LINER lacking broad permitted emission lines like those in Type…
Excess heating of 4He2+ and O6+ relative to H+ downstream of interplanetary shocks
Mall, Urs; Gloeckler, George; Geiss, Johannes +1 more
Using observations made by the solar wind ion composition spectrometer on Ulysses during its trip in the ecliptic plane to Jupiter, we examined the temperature ratios T(4He2+)/T(H+) and T(O6+)/T(H+) across 15 shocks, including forward and reverse shock pairs as well as isolated shocks. The mea…
Mass Segregation and Equipartition of Energy in Two Globular Clusters with Central Density Cusps.
Sosin, Craig
We begin by presenting the analysis of a set of deep B- and V-band images of the central density cusp of the globular cluster M30 (NGC 7099), taken with the Faint Object Camera aboard the Hubble Space Telescope. These images are the first to resolve lower-mass main-sequence stars in the cluster's central 10". From the positions of individual stars…
Abundances of the ^3^He star 3 CEN A (B5 IIIp) from ultraviolet IUE spectra.
Hack, M.; Parthasarathy, M.; Castelli, F.
High resolution (0.010-0.025nm) IUE ultraviolet spectra of the peculiar ^3^He star 3 Cen A were analyzed in the whole 120-320nm region. Abundances were derived from the comparison of the observed and computed spectra. For computing spectra a Kurucz ATLAS9 model with parameters T_eff_=17500K, logg=3.8, and microturbulent velocity ξ=0km/s was adopte…
Analyzing X-ray variability by linear state space models
Timmer, J.; Konig, M.
In recent years, autoregressive models have had a profound impact on the description of astronomical time series as the observation of a stochastic process. These methods have advantages compared with common Fourier techniques concerning their inherent stationarity and physical background. However, if autoregressive models are used, it has to be t…
Detection of Bernstein wave forbidden bands in the Jovian magnetosphere: A new way to measure the electron density
Forsyth, R. J.; Moncuquet, Michel; Meyer-Vernet, Nicole +2 more
We analyze the power spectra measured by the radio receiver of the Unified Radio and Plasma Wave experiment on Ulysses during its passage through the Jovian inner magnetosphere from ~9RJ in the outskirts of the Io plasma torus to ~13RJ near the plasma sheet. Below the plasma frequency fp, these spectra are weakly b…
Radial velocities and iron abundances of field RR Lyraes. II.
Garrido, R.; Solano, E.; Barnes, T. G. +1 more
This is the second of the papers devoted to derive radial velocities and iron abundances of field RR Lyraes observed by HIPPARCOS. Our abundances show good agreement with those in the literature obtained both from photometric (Delta S index) and spectroscopic methods. Binary candidates and stars misclassified as RR Lyraes in the original HIPPARCOS…
Is the geoeffectiveness of the 6 January 1997 CME predictable from solar observations?
Hoeksema, J. T.; Zhao, X. P.
We present a prediction scheme for specifying the duration and maximum strength of the southward IMF within a magnetic cloud from observations of the disappearing filament associated with the coronal mass ejection and the photospheric magnetic field made near the filament disappearing. Using this scheme we were able to predict that the Earth direc…
Charge Transfer between Neutral Atoms and Highly Ionized Species: Implications for ISO Observations
Korista, K. T.; Ferland, G. J.; Dalgarno, A. +1 more
We estimate rate coefficients for charge transfer between neutral hydrogen and helium and moderately to highly ionized heavy elements. Although charge transfer does not have much influence on hot collisionally ionized plasmas, its effects on photoionized plasmas can be profound. We present several photoionization models that illustrate the signifi…
Detection of Self-reversed Lyα Lines from the Jovian Aurorae with the Hubble Space Telescope
Ballester, Gilda E.; Prangé, Renée; Clarke, John T. +5 more
We present Lyα profiles taken at high spectral resolution (~70 mÅ) in the Jovian aurorae, using the Goddard High-Resolution Spectrograph aboard the Hubble Space Telescope. They exhibit a strong central reversal, reminiscent of solar and stellar spectra. This effect was predicted by models as a consequence of radiative transfer effects on photons e…