Search Publications
Abundance and origin of the CH_n_^+^ ions in the coma of comet P/Halley
Altwegg, K.; Balsiger, H.; Geiss, J.
We analyzed data in the mass/charge group 12-16 amu/e from the High Intensity Sensor (HIS) of the Ion Mass Spectrometer IMS on board the spacecraft Giotto during the comet Halley flyby. The most abundant ion in this mass/charge range is CH_3_^+^. Its parent molecules are either CH_2_, CH_3_ or CH_4_. Hereby, the methane abundance serves as an impo…
Jupiter Radio Bursts and Particle Acceleration
Desch, Michael D.
Particle acceleration processes are important in understanding many of the Jovian radio and plasma wave emissions. However, except for the high-energy electrons that generate synchrotron emission following inward diffusion from the outer magnetosphere, acceleration processes in Jupiter's magnetosphere and between Jupiter and Io are poorly understo…
The Chromospheric Structure of the Cool Giant Star G Herculis
Johnson, Hollis R.; Luttermoser, Donald G.; Eaton, Joel
Non-Local Thermodynamic Equilibrium (LTE) calculations of semiempirical chromospheric models are presented for 30 g Her (M6 III). This star is one of the coolest (Teff = 3250 K) SRb (semiregular) variable stars and has a mass perhaps as great as 4 solar mass. Chromospheric features we have observed in its spectrum include Mg II h and k;…
A Statistical Equilibrium Analysis of Interstellar CO toward zeta Ophiuchi as Recorded by the Goddard High Resolution Spectrograph
Smith, Andrew M.; Bruhweiler, Frederick C.; Lyu, Cheng-Hsuan
High-resolution and high signal-to-noise ratio echelle observations made by the Goddard High Resolution Spectrograph (GHRS), aboard the Hubble Space Telescope, of molecular (12)C(16)O and (13)C(16)O in the absorbing gas toward zeta Oph are reported. A statistical equilibrium model, incorporating a different way of dealing with the radiation field …
Comparison of New Experimental and Astrophysical f-Values for Some RU II Lines, Observed in HST Spectra of chi LUPI
Wahlgren, Glenn M.; Leckrone, David S.; Johansson, Sveneric G. +6 more
We report an experimental absolute oscillator strengths for 18 UV lines of Ru II, obtained by combining laser-induced flourescence measurements of radiative lifetimes and branching fractions from line intensities in a calibrated Fourier-transform spectrum Hubble Space Telescope/Goddard High Resolution Spectrograph (HST/GHRS) observations of the sp…
High-resolution spectroscopy of two young stars between the Magellanic Clouds
Howarth, I. D.; Dufton, P. L.; Hambly, N. C. +3 more
High-resolution echelle spectra of one main sequence B-type star and one B-type supergiant in the Bridge between the Magellanic Clouds have been obtained using the 3.9-m Anglo-Australian Telescope. These spectra have been analyzed in conjunction with IUE low-resolution observations by using ATLAS9 LTE model atmosphere techniques, to derive the ste…
Faint blue stars in the core of NGC 6397.
Paresce, F.; de Marchi, G.
The inner core of the globular cluster NGC 6397 within approximately 6 arcsecs of the geometrical centre has been investigated with high resolution deep images taken through several medium- and broad-band UV filters with the Faint Object Camera (FOC) on board the Hubble Space Telescope (HST). Approximately 110 stars down to instrumental magnitude …
Narrowband HST Imagery of the Young Planetary Nebula Henize 1357
Bobrowsky, M.
We present Hubble Space Telescope (HST) Planetary Camera observations showing the first optically resolved images of the planetary nebula Henize 1357 . The small size of this object has heretofore precluded optical investigations of its morphology. In H-beta, He 3-1357 appears to have an equatorial ring of enhanced density tilted approximately 56 …
Low-Velocity Variability in the Stellar Wind of HD 152408 (O8: Iafpe)
Fullerton, A. W.; Prinja, Raman K.
We describe high-quality, spectroscopic time series observations of variability at low velocities in the stellar wind of the extreme O-supergiant HD 152408. These observations were obtained during a monitoring campaign coordinated between Australia and Chile in 1992 July. Systematic variability on hourly time scales is particularly apparent in the…
Gamma-Ray Pulsar Studies with COMPTEL
Strong, A. W.; Grenier, I. A.; Diehl, R. +10 more
Since the launch of the Compton Gamma-Ray Observatory (CGRO) the number of detected gamma-ray pulsars increased from two to six. COMPTEL, on-board CGRO and sensitive to gamma-rays with energies between approximately 0.7 and 30 MeV, detected three of these unambiguously. The classical Crab and Vela pulsars have been observed on several occasions an…