Search Publications
A Test of Galaxy Evolutionary Models via Angular Sizes
Casertano, Stefano; Im, Myungshin; Tyson, J. Anthony +2 more
The relationship between angular size, magnitude, and redshift of faint galaxies is explored as a potential tool to distinguish between different galaxy evolutionary models. Different models, based on merging, mild luminosity evolution, and no evolution, lead to different predictions of the angular size distribution, redshift-size relation, and ma…
The electron temperature in the inner coma of comet P/Halley.
Eberhardt, P.; Krankowsky, D.
From the CH_3_OH_2_^+^/H_3_O^+^ and H_3_O^+^/H_2_O^+^ ratios measured by the Giotto Neutral Mass Spectrometer in the inner coma (distance <20000km) of comet P/Halley we derive two independent electron temperature profiles. They agree very well and the electron temperature T_e_ increases gradually from =~100K at 2000km to =~900K at 8500km follow…
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…