Search Publications
Mid-infrared and far-ultraviolet observations of the star-forming ring of M 31
Sauvage, M.; Pagani, L.; Lequeux, J. +4 more
We present mid-IR images of a 15\arcminx15' field in the south-west part of the Andromeda galaxy M 31 obtained with the ISOCAM camera (6'' pixels) on board ISO. These broad-band images complement spectro-imaging observations of smaller fields (Cesarsky et al. \cite{Cesarsky98}). We also present a 20'' resolution far-UV image of a larger field at 2…
Mechanisms for Latitudinal Transport of Energetic Particles in the Heliosphere
Fisk, L. A.; Jokipii, J. R.
Energetic particles in the heliosphere, from relatively low-energy particles which are accelerated in Corotating Interaction Regions (CIRs) to galactic cosmic rays, are observed to propagate relatively easily in heliographic latitude. Two mechanisms for this transport appear possible: cross-field diffusion, or, in a recent model for the heliospher…
Detection of H2 Pure Rotational Line Emission from the GG Tauri Binary System
van Dishoeck, Ewine F.; Blake, Geoffrey A.; Hogerheijde, Michiel R. +2 more
We present the first detection of the low-lying pure rotational emission lines of H2 from circumstellar disks around T Tauri stars, using the Short Wavelength Spectrometer on the Infrared Space Observatory. These lines provide a direct measure of the total amount of warm molecular gas in disks. The J=2-->0 S(0) line at 28.218 µ…
Goddard High-Resolution Spectrograph Observations of the B III Resonance Doublet in Early B Stars: Abundances and Isotope Ratios
Wahlgren, Glenn M.; Proffitt, Charles R.; Jönsson, Per +2 more
Boron abundances and isotope ratios in two early B stars have been measured by using the Hubble Space Telescope's Goddard High-Resolution Spectrograph (GHRS) in order to observe the B III resonance doublet near 2066 Å. We also report new experimental and theoretical results for the wavelengths, isotope shift, and hyperfine structure of these boron…
Stability of Neptune's ring arcs in question
Schneider, Glenn; Dumas, Christophe; Terrile, Richard J. +2 more
Although all four of the gas-giant planets in the Solar System have ring systems, only Neptune exhibits `ring arcs'-stable clumps of dust that are discontinuous from each other. Two basic mechanisms for confining the dust to these arcs have been proposed. The firstrelies on orbital resonances with two shepherding satellites, while the second invok…
HUBBLE SPACE TELESCOPE Imaging of the Host Galaxies of High-RedshiftRadio-loud Quasars
Lehnert, Matthew D.; Heckman, Timothy M.; Miley, George K. +1 more
We present rest-frame UV and Lyα images of spatially resolved structures (``hosts'') around five high-redshift radio-loud quasars obtained with the WFPC2 camera on the Hubble Space Telescope (HST). The quasars were imaged with the PC1 through the F555W (``V''-band) filter, which at the redshifts of the quasars (2.1<z<2.6) have central wavele…
Stellar Masses, Kinematics, and White Dwarf Composition for Three Close DA+DME Binaries
Vennes, Stéphane; Thorstensen, John R.; Polomski, Elisha F.
We determine the mass functions and mass ratios for three close white dwarf plus red dwarf binaries (EUVE J0720-317, 1016-053, and 2013+400). Hubble Space Telescope Goddard High-Resolution Spectrograph spectra of the He II λ1640 and C IV λ1550 spectral lines trace the white dwarf orbital motion, and Hamilton Spectrograph echelle spectra (Lick Obse…
The Starburst-Active Galactic Nucleus Connection in Active Galaxies: The MassiveNuclear Star-Forming Disk in NGC 4303
Colina, L.; Arribas, S.
Two-dimensional spectroscopy of the low-redshift active galaxy NGC 4303 obtained with the Two-Dimensional Fiber ISIS System is presented. The ionization structure and velocity field of the nuclear region of this galaxy, where a compact UV-bright spiral structure connected with the UV-bright core has been detected with the Hubble Space Telescope (H…
Composition of the Volatile Material in Halley's Coma from In Situ Measurements
Altwegg, K.; Balsiger, H.; Geiss, J.
The investigation of the volatile material in the coma of comets is a key to understanding the origin of cometary material, the physical and chemical conditions in the early solar system, the process of comet formation, and the changes that comets have undergone during the last 4.6 billion years. So far, in situ investigations of the volatile cons…
New HST Observations of the Halo Gas of NGC 3067: Limits on the Extragalactic Ionizing Background at Low Redshift and the Lyman Continuum Escape Fraction
Shull, J. Michael; Stocke, John T.; Tumlinson, Jason +1 more
We present ultraviolet spectroscopy from HST/GHRS and reanalyze existing Hα images of the quasar/galaxy pair 3C 232/NGC 3067 and of the halo gas associated with NGC 3067. The spectra permit measurement of, or limits on, the column densities of Fe I, Fe II, Mg I, and Mg II in the absorbing cloud. Two distinct models of the extragalactic radiation f…