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Abundance variations in the solar wind
Geiss, J.; Gloeckler, G.; von Steiger, R. +1 more
The solar wind (SW) allows us to probe the solar material in situ, particularly its composition, without the need to fly a spacecraft to inhospitably small heliocentric distances. However, it turns out that this plasma source is biased with respect to the photosphere. Elements with a low first ionization potential (FIP) are overabundant by a facto…
Low-mass stars in globular clusters. III. The mass function of 47 Tucanae.
Paresce, F.; de Marchi, G.
We have used the WFPC2 on board HST to investigate the stellar population in a field located 4'6 E of the center of the globular cluster 47 Tuc (NGC 104), close to the half-mass radius, through wide band imaging at 606 and 812nm. A total of ~3000 stars are accurately classified by two-color photometry to form a color-magnitude diagram extending do…
Two years of Ulysses dust data
Hamilton, D. P.; Grün, E.; Kissel, J. +16 more
From October 18, 1990 to February 8, 1992 the Ulysses spacecraft traversed interplanetary space between the Earth and Jupiter; at Jupiter the spacecraft was deflected below the ecliptic onto a highly-inclined orbit ( i∼80°). Here, we report on dust impact data obtained from launch until the end of 1992, nearly a year after the Jupiter flyby. Durin…
Atomic Physics with the Goddard High-Resolution Spectrograph on the Hubble Space Telescope. II. Oscillator Strengths for Singly Ionized Iron
Savage, Blair D.; Cardelli, Jason A.
Moderate-to-high signal-to-noise interstellar absorption line data, obtained with the Goddard High-Resolution Spectrograph aboard the Hubble Space Telescope toward β1 Sco, HD 18100, and µ Col, are used to derive absolute oscillator strengths (f-values) for a number of weak and strong ultraviolet resonance transitions of Fe II span…
Solar wind electron parameters from quasi-thermal noise spectroscopy and comparison with other measurements on Ulysses
Maksimovic, M.; Phillips, J. L.; Canu, P. +4 more
Plasma thermal noise spectroscopy was used for the first time on a large scale on the Ulysses radio receiver data to measure the solar wind electron density and temperature in the ecliptic plane. The validity and limitations of the results obtained with this method are discussed. nearly simultaneous measurements of the electron density and tempera…
Magnetic Holes in the Solar Wind and Their Relation to Mirror Mode Structures
Balogh, A.; Tsurutani, B. T.; Smith, E. J. +4 more
Data obtained by the Ulysses magnetometer and solar wind analyzer have been combined to study the properties of magnetic holes in the solar wind between 1 and 5.4 AU and to 23° south latitude. Although the plasma surrounding the holes was generally stable against the mirror instability, there are indications that the holes may have been remnants o…
A Hubble Space Telescope Study of the Underlying White Dwarf in the Dwarf Nova VW Hydri during Quiescence
Szkody, Paula; Sion, Edward M.; Cheng, Fu-Hua +1 more
We have analyzed a far-ultraviolet spectrum of the dwarf nova VW Hyi obtained during quiescence with the Hubble Space Telescope Faint Object Spectrograph (HST FOS). The observation occurred 10 days after the return to optical quiescence from a superoutburst of VW Hyi. The spectrum reveals a very strong Stark-broadened Ly-alpha absorption with narr…
The sensitivity of the size distribution to the grain dynamics: simulation of the dust flux measured by GIOTTO at P/Halley.
Fulle, M.; Mennella, V.; Colangeli, L. +2 more
A cometary dust emission model, based on rigorous keplerian dynamics, is developed and, for the first time, the dependence of fluence on the probability distribution of the dust ejection velocity vector is demonstrated. The results are compared with the fluences measured by the DIDSY experiment on board the GIOTTO spacecraft during the Halley's fl…
PKS 2349-014: A Luminous Quasar with Thin Wisps, a Large Off-Center Nebulosity, and a Close Companion Galaxy
Schneider, Donald P.; Bahcall, John N.; Kirhakos, Sofia
Hubble Space Telescope (HST) images (WFC2) of PKS 2349-014 show that this luminous nearby quasar is interacting with diffuse (presumably galactic) material. Two thin wisps that have a total extent of about 20 kpc (for H0 = 100 km s-1 Mpc-1 and Omega 0 = 1.0) are observed to approximately surround the quasar. One of the wisps appears to pass throug…
An independent calibration of stellar ages: Hubble Space Telescope observations of white dwarfs at V=25
Gilmore, Gerard; Jones, D. H. P.; von Hippel, Ted
The white dwarf luminosity function of a stellar cluster will have a sharp truncation at a luminosity which is determined by the time since formation of the first white dwarfs in that cluster. Calculation of the dependence of this limiting luminosity on age requires relatively well-understood physics and is independent of stellar evolutionary mode…