Search Publications
The Cosmic-Ray Radioactive Nuclide 36Cl and Its Propagation in the Galaxy
Simpson, J. A.; Connell, J. J.; DuVernois, M. A.
Radioactive 36Cl has been resolved from 35Cl and 37Cl for the first time in the cosmic radiation with measurements obtained from the high-resolution High-Energy Telescope (HET) carried on the NASA-ESA Ulysses spacecraft. Within the framework of a homogeneous propagation model wherein all 36Cl is of spall…
Wind Velocity Variations in the Luminous Blue Variable-Type Erupting Star of the Wolf-Rayet Binary HD 5980
Koenigsberger, G.; Auer, L. H.; Georgiev, L. +1 more
We present the wind velocity and UV luminosity variations in the Wolf-Rayet system HD 5980 obtained over a time span during which one of the stars of the system was transformed into a luminous blue variable and underwent an eruption. We are able to separate the velocity components of the two stars in the system: a stable velocity component at -170…
Discovery of a New Quadruple Lens HST 1411+5211
Barrientos, L. Felipe; Fischer, Philippe; Schade, David
Gravitational lensing is an important tool for probing the mass distribution of galaxies. In this Letter, we report the discovery of a new quadruple lens HST 1411+5211 found in archived Wide-Field Planetary Camera 2 images of the galaxy cluster CL 140933+5226. If the galaxy is a cluster member, then its redshift is z=0.46. The images of the source…
The Electron Pressure in the Solar Lower Transition Region Determined from O V and Si III Density-sensitive Line Ratios
Wilhelm, K.; Doschek, G. A.; Warren, H. P. +3 more
We determine the electron density at the temperatures of formation of O+4 and Si+2 ions, which are about 2.5 × 105 and 3.2 × 104 K in ionization equilibrium, respectively. These temperatures occur in the lower transition region of the Sun's atmosphere and allow a test of the often invoked assumption of c…
HST Spectra of the Jovian Ultraviolet Aurora: Search for Heavy Ion Precipitation
Trafton, L. M.; Waite, J. H.; Gérard, J. -C. +3 more
Ultraviolet spectra using Hubble Space Telescope sampled between 1250 and 1680 Å at spectral resolution <=0.57 Å are reported for characteristically bright regions of Jupiter's morning and afternoon northern aurora. Several observed spectra exhibit sharply enhanced resolution. We interpret this as bright auroral emission foreshortened on the mo…
Small-Scale Structure in the Lyα Forest at High Redshift
Impey, C. D.; Petry, C. E.; Foltz, C. B.
We have obtained spectra of the four components of the system B1422+231 with HST's Faint Object Spectrograph in order to study spatial inhomogeneities and velocity variations in the absorbers which are pierced by the four lines of sight. The four images are well resolved, and the spectra clearly show the system is a lensed quasar; a new redshift b…
Classical Cepheid Masses: U Aquilae
Evans, Nancy Remage; Carpenter, Kenneth; Robinson, Richard +2 more
We have obtained medium-resolution spectra (λ/Δλ ~ 20,000) of the hot binary companion to the classical Cepheid U Aql with the Goddard High Resolution Spectrograph on the Hubble Space Telescope (HST). These have been used to determine the orbital velocity amplitude. Combining this with the orbital velocity amplitude of the Cepheid from the ground-…
A Realistic Grid of Models for the Gravitationally Lensed Einstein Cross (Q2237+0305) and Its Relation to Observational Constraints
Turnshek, David A.; Chae, Kyu-Hyun; Khersonsky, Valery K.
A detailed study of a power-law lens model is presented for the gravitational lens system Q2237+0305, also known as the Einstein Cross. The adopted three-dimensional distribution for the mass of the lens is more realistic than in previous models and is described by ρ(X, Y, Z) = ρ0[1 + (X/a)2 + (Y/b)2 + (Z/c)2<…
Stereoscopic Observations of Solar Hard X-Ray Flares Made by ULYSSES and YOHKOH
Hurley, K.; Boer, M.; Niel, M. +4 more
The Solar X-Ray/Cosmic Gamma-Ray Burst Experiment aboard the interplanetary spacecraft Ulysses has provided extensive observations of solar hard X-ray flares from a variety of angles with respect to the Sun-Earth line. During the period 1991 October-1993 June, Ulysses observed 13 flares that were also observed by the X-ray instruments aboard the J…
Peaks and Troughs in Helioseismology: The Power Spectrum of Solar Oscillations
Rosenthal, C. S.
I present a matched-wave asymptotic analysis of the driving of solar oscillations by a general localized source. The analysis provides a simple mathematical description of the asymmetric peaks in the power spectrum in terms of the relative locations of eigenmodes and troughs in the spectral response. It is suggested that the difference in measured…