Search Publications
The Apparently Normal Galaxy Hosts for Two Luminous Quasars
Schneider, Donald P.; Bahcall, John N.; Kirhakos, Sofia
HST images (with WFPC2) of PHL 909 (z = 0.171) and PG 0052+251 (z = 0.155) show that these luminous radio-quiet quasars each occur in an apparently normal host galaxy. The host galaxy of PHL 909 is an elliptical galaxy (∼E4), and the host of PG 0052+251 is a spiral (∼Sb). Both host galaxies are several tenths of a magnitude brighter than L*
Combined stellar structure and atmosphere models for massive stars. II. Spectral evolution on the main sequence.
Schaerer, D.; Schmutz, W.; de Koter, A. +1 more
In Schaerer et al. (1995, Paper I) we have presented the first ``combined stellar structure and atmosphere models'' (CoStar) for massive stars, which consistently treat the entire mass loosing star from the center out to the outer region of the stellar wind. The models use up-to-date input physics and state-of-the-art techniques to model both the …
First data from the ISOPHOT FIR Serendipity survey.
Kessler, M. F.; Burgdorf, M.; Lemke, D. +10 more
The ISOPHOT Serendipity Survey fills the otherwise unused slew time between ISO's fine pointings with measurements in an unexplored wavelength regime near 200µm. First results of the Serendipity Survey demonstrate its capabilities in the detection of extragalactic point sources as well as in investigations of the galactic infrared cirrus. Wi…
Global imaging of Mars by Hubble space telescope during the 1995 opposition
Bell, James F.; Wolff, Michael J.; Clancy, R. Todd +3 more
Hubble space telescope (HST) imaging of Mars near the 1995 opposition resulted in excellent synoptic-scale images of the planet during the spring season in the northern hemisphere. Because this season coincides with the aphelion position of Mars in its orbit, it is therefore the most difficult for ground based observation because of the relatively…
The Relationship between the High-Energy Continuum and Emission Lines in Quasars: A Low-Redshift Sample
Green, Paul J.
Photoionization models dictate that many prominent quasar emission lines are sensitive to both the luminosity and shape of the quasars high- energy continuum-primarily the extreme ultraviolet (EUV) and soft X-ray continuum. Unfortunately, the EUV band is severely obscured by Galactic absorption. Using data from the adjacent UV and soft X-ray bandp…
Far-Ultraviolet Spectra of Broad Absorption Line QSOs and Constraints on Models for the Ionization Structure and Metallicity of the BAL-Region Gas
Turnshek, David A.; Weymann, Ray J.; Kopko, Michael, Jr. +3 more
Hubble Space Telescope Faint Object Spectrograph G270H spectra of four moderate-to high-redshift broad absorption line (BAL) QSOs are presented. In addition, evidence is discussed that indicates that the gas that gives rise to the BALs has nonuniform ionization and enhanced abundances. In the context of a photoionization model, ionization paramete…
The Elemental Composition of the Galactic Cosmic-Ray Source: ULYSSES High-Energy Telescope Results
Duvernois, M. A.; Thayer, M. R.
The nucleosynthetic origin of the galactic cosmic-ray sources (GCRS) is a matter of some considerable interest (e.g., Leske; Connell & Simpson; DuVernois et al.). Any understanding of this origin requires an accurate determination of the source elemental abundances. These abundances are determined by comparing the Ulysses High-Energy Telescope…
The shape and strength of circumstellar PAH emission bands.
Waters, L. B. F. M.; Beintema, D. A.; de Graauw, T. +9 more
We discuss the shape and strength of the emission bands observed in Short Wavelength Spectrometer (SWS) spectra of three carbon-rich evolved stars (Beintema et al., 1996A&A...315L.253B). The emission bands, due to stretching and bending modes of C-C and C-H bonds in Polycyclic Aromatic Hydrocarbons (PAHs), show large difference in strength and…
Latitudinal dependence of the radial IMF component: Coronal imprint
Smith, E. J.; Suess, S. T.
Measurements by Ulysses have confirmed that there is no significant gradient with respect to heliomagnetic latitude in the radial component, Br, of the interplanetary magnetic field. In the corona, the plasma β is ≪ 1, except directly above streamers, so longitudinal and latitudinal gradients in field strength will relax due to the tran…
A new maximum likelihood method for luminosity calibrations.
Luri, X.; Figueras, F.; Torra, J. +1 more
A new statistical parallax method using the Maximum Likelihood principle is presented, allowing the simultaneous determination of a luminosity calibration, kinematic characteristics and spatial distribution of a given sample. This method has been developed for the exploitation of the Hipparcos data and presents several improvements with respect to…