Search Publications
Broad emission features in QSOs and active galactic nuclei. II. New observations and theory of Fe II and HI emission.
Netzer, H.; Wills, B. J.; Wills, D.
Seven QSOs of low to intermediate redshift are characterized on the basis of: 320-850-nm spectra obtained with the UVITS spectrograph and image-dissector scanner at the f/9 Cassegrain focus of the 2.7-m reflecting telescope at McDonald Observatory; improved model calculations for the Fe II, Mg II, and Balmer lines and the Balmer continuum; and the…
The visible and infrared extinction law and the gas-to-dust ratio in the Small Magellanic Cloud.
Bouchet, P.; Lequeux, J.; Prevot, L. +2 more
Photometric observations in the UBVJHK bands have been made for 23 O-B3 stars in the Small Magellanic Cloud, for which the MK spectral type and luminosity class have been determined. Also derived from these data are the extinction curve in the visible and the near-infrared. This curve is very close to the curves in the Galaxy and the Large Magella…
The nucleus of M 82 at radio and X-ray bands : discovery of a new radio population of supernova candidates.
Kronberg, P. P.; Biermann, P.; Schwab, F. R.
Detailed VLA radio maps are presented of the continuum radio emission in M82 and the X-ray emission from the HRI of the Einstein X-ray satellite. The authors have discovered more than 40 new radio sources within 300 pc of M82's nucleus. It is argued that nearly all of these sources are radio supernovae or supernova remnants and their radio luminos…
EXOSAT observations of a strong soft X-ray excess in MKN 841.
Culhane, J. L.; Fabian, A. C.; Branduardi-Raymont, G. +6 more
EXOSAT observations of the spectrum of the Seyfert 1 galaxy MKN 841 show that it is well-fitted by a power law of photon index 1.6, similar to that of other Seyferts, and a large additional soft component. The X-ray luminosity over the observed band exceeds 4×1044erg s-1. A single-temperature blackbody fit to the soft X-rays …
Galactic interstellar abundance surveys with IUE. I. Neutral hydrogen
Shull, J. M.; van Steenberg, M. E.
A survey is initiated of interstellar densities, abundances, and cloud structure in the Galaxy, using the International Ultraviolet Explorer. From high-resolution (0.1-A) spectra, interstellar column densities are derived toward 244 early-type stars by fitting the damping wings of the Ly-alpha absorption line. Published B-V photometry is used to d…
Interstellar extinction variations in the Large Magellanic Cloud.
Fitzpatrick, E. L.
The properties of ultraviolet interstellar extinction in the Large Magellanic Cloud (LMC) are investigated, with particular emphasis on the issue of regional variability. New IUE observations of reddened and standard stars are combined with existing data from the IUE archives. The author finds essentially identical extinction properties toward 12 …
The hybrid spectrum of the LMC hypergiant R 126.
Stahl, O.; Leitherer, C.; Zickgraf, F. -J. +2 more
An extensive spectroscopic (1150 - 6700 Å) and photometric (UBVRIJHKLMN) study of the peculiar LMC hypergiant R126 has been carried out. The authors derive stellar parameters Teff = 22,500K, R = 72 R_sun; and Mbol = -10.5. The corresponding spectral type is B0.5 Ia+. An estimate of the initial and present mass lead…
The evolution of chromospheric activity and the spin-down of solar-type stars.
Simon, T.; Boesgaard, A. M.; Herbig, G.
The authors report on observations made with the IUE satellite of nearly two dozen F7 - G2 dwarfs, dated on the basis of their surface Li content in order to examine the age dependence of ultraviolet chromospheric and transition region emission lines. The IUE data for solar-type stars are compared with observations of T Tauri stars (both published…
Spectrophotometric and model-atmosphere analyses of the hot DO and DAO white dwarfs from the Palomar-Green survey.
Wesemael, F.; Green, R. F.; Liebert, J.
Recent optical and spectrophotometric observations of all currently known DAO and DO hot white dwarf candidates from the Palomar-Green Survey are presented. The optical observations were carried out using the Kitt Peak National Observatory Intensified Image Dissector Scanner (IIDS) system, the Multiple Mirror Telescope (MMT), and two photon-counti…
The galactic ridge observed by Exosat
Warwick, R. S.; Watson, M. G.; Turner, M. J. L. +1 more
We have used Exosat to map the distribution of X-ray emission in the galactic plane. In addition to numerous point sources, the map reveals a narrow continuous ridge of emission which extends along the galactic plane either side of the galactic centre out to ~40° longitude. The origin of this feature remains uncertain although a major contribution…