Search Publications
Intrinsic Absorption Lines in Seyfert 1 Galaxies. I. Ultraviolet Spectra from the Hubble Space Telescope
Mushotzky, Richard F.; Crenshaw, D. Michael; Maran, Stephen P. +3 more
We present a study of the intrinsic absorption lines in the ultraviolet spectra of Seyfert 1 galaxies. The study is based on spectra from the Hubble Space Telescope and includes the Seyfert 1 galaxies observed with the Faint Object Spectrograph and Goddard High-Resolution Spectrograph at spectral resolutions of λ/Δλ~1000-20,000 with good signal-to…
SOHO/EIT Observations of the 1997 April 7 Coronal Transient: Possible Evidence of Coronal Moreton Waves
Michels, D. J.; Thompson, B. J.; Gurman, J. B. +7 more
We report observations obtained with the Extreme ultraviolet Imaging Telescope (EIT) on board SOHO of a large-scale coronal transient propagating across the disk of the Sun at a speed of 250 km s-1, in apparent association with a flare and coronal mass ejection. The observations consist of a series of images taken in the Fe XII 195 Å ba…
Stellar Iron Abundances: Non-LTE Effects
Thévenin, F.; Idiart, T. P.
We report new statistical equilibrium calculations for Fe I and Fe II in the atmosphere of late-type stars. We used atomic models for Fe I and Fe II having, respectively, 256 and 190 levels, as well as 2117 and 3443 radiative transitions. Photoionization cross sections are from the Iron Project. These atomic models were used to investigate non-LTE…
A comparative HST imaging study of the host galaxies of radio-quiet quasars, radio-loud quasars and radio galaxies - I
McLure, R. J.; Dunlop, J. S.; Hughes, D. H. +3 more
We present the first results from a major HST WFPC2 imaging study aimed at providing the first statistically meaningful comparison of the morphologies, luminosities, scalelengths and colours of the host galaxies of radio-quiet quasars, radio-loud quasars and radio galaxies. We describe the design of this study and present the images that have been…
A Large Mid-Infrared Spectroscopic and Near-Infrared Imaging Survey of Ultraluminous Infrared Galaxies: Their Nature and Evolution
Lutz, D.; Genzel, R.; Rigopoulou, D. +3 more
We present a low-resolution mid-infrared spectroscopic survey of an unbiased sample of 62 ultraluminous infrared galaxies (ULIRGs) (LIR>1012Lsolar, z<=0.3) using ISOPHOT-S on board the Infrared Space Observatory (ISO). For comparison, we also present ISOPHOT-S spectra for 23 active galactic nuclei (AGNs) and …
A Comprehensive Spectral and Variability Study of Narrow-Line Seyfert 1 Galaxies Observed by ASCA. II. Spectral Analysis and Correlations
Leighly, Karen M.
I present a comprehensive and uniform analysis of 25 ASCA observations from 23 narrow-line Seyfert 1 galaxies (NLS1s). The spectral analysis and correlations are presented in this paper; the reduction and time series analysis are presented in the companion paper. A maximum likelihood analysis confirms that the hard X-ray photon index is significan…
Magnetohydrodynamic modeling of the solar corona during Whole Sun Month
Thompson, B. J.; Forsyth, R. J.; Biesecker, D. A. +7 more
The Whole Sun Month campaign (August 10 to September 8, 1996) brought together a wide range of space-based and ground-based observations of the Sun and the interplanetary medium during solar minimum. The wealth of data collected provides a unique opportunity for testing coronal models. We develop a three-dimensional magnetohydrodynamic (MHD) model…
An Empirical Model of a Polar Coronal Hole at Solar Minimum
Romoli, M.; Raymond, J. C.; Naletto, G. +28 more
We present a comprehensive and self-consistent empirical model for several plasma parameters in the extended solar corona above a polar coronal hole. The model is derived from observations with the SOHO Ultraviolet Coronagraph Spectrometer (UVCS/SOHO) during the period between 1996 November and 1997 April. We compare observations of H I Lyα and O …
15 Micron Infrared Space Observatory Observations of the 1415+52 Canada-France Redshift Survey Field: The Cosmic Star Formation Rate as Derived from Deep Ultraviolet, Optical, Mid-Infrared, and Radio Photometry
Omont, A.; Eales, S.; Thuan, T. X. +7 more
The Canada-France Redshift Survey 1452+52 field has been deeply imaged with the Infrared Space Observatory using ISOCAM through the LW3 filter (12-18 µm). Careful data analysis and comparison with deep optical and radio data have allowed us to generate a catalog of 78 15 µm sources with both radio and optical identifications. They are …
The Ultraviolet and Optical Continuum Emission in Active Galactic Nuclei: The Status of Accretion Disks
Koratkar, Anuradha; Blaes, Omer
A fundamental component of models of active galactic nuclei (AGNs) is an accretion disk around a supermassive black hole. However, the nature of this accretion disk is not well understood, and current models do not provide a satisfactory explanation of the optical/UV continuum observed in AGNs. In this paper we review the substantial theoretical a…