135 citations · 636 across the 19 of their papers we have counts for
6 papers · 1 filter
Transient Heavy Element Absorption Systems in Novae: Episodic Mass Ejection from the Secondary Star
Robert Williams, Elena Mason, Massimo Della Valle +1
A high-resolution spectroscopic survey of postoutburst novae reveals short-lived heavy element absorption systems in a majority of novae near maximum light, having expansion veloci…
Independent Emission and Absorption Abundances for Planetary Nebulae
Robert Williams, Edward B. Jenkins, Jack A. Baldwin +4
Emission-line abundances have been uncertain for more than a decade due to unexplained discrepancies in the relative intensities of the forbidden lines and weak permitted recombina…
Identification and Characterization of Faint Emission Lines in the Spectrum of the Planetary Nebula IC 418
Brian Sharpee, Jack A. Baldwin, Robert Williams
We present high signal-to-noise echelle spectra of the compact high surface brightness, low ionization planetary nebula IC 418. These reveal 807 emission lines down to intensities…
Comparative Absorption and Emission Abundance Analyses of Nebulae: Ion Emission Densities for IC 418
Robert Williams, Edward B. Jenkins, Jack A. Baldwin +1
Recent analyses of nebular spectra have resulted in discrepant abundances from CNO forbidden and recombination lines. We consider independent methods of determining ion abundances…
VLA Observations of H I in the Helix Nebula (NGC 7293)
Luis F. Rodriguez, W. M. Goss, Robert Williams
We report the detection of 21-cm line emission from H I in the planetary nebula NGC 7293 (the Helix). The observations, made with the Very Large Array, show the presence of a ring…
The Hubble Deep Fields
Henry C. Ferguson, Mark Dickinson, Robert Williams
The Hubble space telescope observations of the northern Hubble deep field, and more recently its counterpart in the south, provide detections and photometry for stars and field gal…