Search Publications

High Carbon in I Zwicky 18: New Results from Hubble Space Telescope Spectroscopy

Garnett, D. R.; Skillman, E. D.; Dufour, R. J. +1 more

We present new measurements of the gas-phase C/O abundance ratio in both the northwest (NW) and southeast (SE) components of the extremely metal-poor dwarf irregular galaxy I Zw 18, based on ultraviolet spectroscopy of the two H II regions using the Faint Object Spectrograph on the Hubble Space Telescope. We determine values of log C/O = -0.63 +/-…

High-Resolution Observations of the Extreme Ultraviolet Sun

Harrison, R. A.; Culhane, J. L.; Fludra, A. +9 more

This paper presents first results of the Coronal Diagnostic Spectrometer (CDS) recently launched aboard the Solar and Heliospheric Observatory (SOHO). CDS is a twin spectrometer, operating in the extreme ultraviolet range 151-785 Å. Thus, it can detect emission lines from trace elements in the corona and transition region which will be used to pro…

The Wide-Band Plasma Wave Investigation

Gurnett, D. A.; Kirchner, D. L.; Huff, R. L.

Application of Spectroscopic Diagnostics to Early Observations with the SOHO Coronal Diagnostic Spectrometer

Young, P. R.; Mason, H. E.; Harrison, R. A. +4 more

The Coronal Diagnostic Spectrometer (CDS) has as a scientific goal the determination of the physical parameters of the solar plasma using spectroscopic diagnostic techniques. Absolute intensities and intensity ratios of the EUV spectral emission lines can be used to obtain information on the electron density and temperature structure, element abun…

The solar disk spectrum between 660 and 1175 Anstroms (first order) obtained by SUMER on SOHO

Wilhelm, K.; Curdt, W.; Lemaire, P. +3 more

SUMER -- Solar Ultraviolet Measurements of Emitted Radiation -- onboard of SOHO -- Solar and Heliospheric Observatory -- obtained its first spectrum on January 25, 1996 near the north polar limb. The range from 660 Angstroms to 1175 Angstroms which has never before been observed with such a good spectral resolution contains a wealth of spectroscop…

Lyman-Alpha Absorption and the D/H Ratio in the Local Interstellar Medium

Vidal-Madjar, A.; Audouze, J.; Landsman, W. +5 more

Using the Goddard High Resolution Spectrograph onboard the Hubble Space Telescope, we have observed Lyα absorption against stellar chromospheres along six lines of sight, with additional observations of the Mg II H and K lines along five of the lines of sight and Fe II absorption along four of the lines of sight. We found absorption near the proje…

HST and Merlin Observations of 3C 264--A Laboratory for Jet Physics and Unified Schemes

Baum, Stefi A.; O'Dea, Christopher P.; Sparks, William B. +10 more

We present new HST optical continuum and emission line WFPC2 images and MERLIN radio observations of 3C 264 at ~0.1" resolution. The jet is well resolved in both the optical and radio images. In addition, we report the discovery of an apparent optical ``ring'' at a projected radius of ~300-400 pc. The ring is most likely the manifestation of absor…

A New Measurement of the Electron Density in the Local Interstellar Medium

Wood, Brian E.; Linsky, Jeffrey L.

Using the echelle-A grating of the Goddard High-Resolution Spectrograph, we have observed the C II λλ1335, 1336 emission lines of the nearby (d = 13.3 pc) star system Capella (G8 III + G1 III). Interstellar C II absorption features are detected within both stellar emission lines. The ground-state and excited-state C II column densities derived fro…

Hubble Space Telescope Imaging of z >= 0.4 Quasar Host Galaxies Selected by Quasar Radio and Optical Properties

Foltz, Craig B.; Hooper, Eric J.; Impey, Chris D.

A sample of 16 quasars selected from the Large Bright Quasar Survey in the redshift range 0.4 < z < 0.5 has been imaged in the R band with the Planetary Camera on the WFPC2 instrument of the Hubble Space Telescope. The host galaxy magnitudes are mostly similar to or brighter than L*, and the host luminosity is positively correlated with the …

Multiwavelength Observations of 3C 273 in 1993-1995

McHardy, I.; Ghisellini, G.; McBreen, B. +30 more

We present the results of the multiwavelength campaigns on 3C 273 in 1993-1995. During the observations in late 1993, this quasar showed an increase of its flux for energies >=100 MeV from about 2.1 × 10^-7 photons cm^-2 s^-1 to approximately 5.6 × 10^-7 photons cm^-2 s^-1 during a rad…