Search Publications
High energy gamma rays from the VELA pulsar : long-term variability and energy distribution.
Grenier, I. A.; Hermsen, W.; Clear, J.
New results on the temporal and spectral characteristics of the high energy (50 MeV to 5 GeV) gamma ray emission from the Vela pulsar are presented. A new sensitive analysis method using maximum likelihood techniques has been applied to the final COS-B dataset. The whole pulsed flux is found to exhibit long term variability. The energy spectrum of…
Hard X-Ray Emission from a Type 2 Seyfert Galaxy (NGC 1068)
Elvis, Martin; Lawrence, A.
EXOSAT observations of the type 2 Seyfert galaxy NGC 1068 have detected a source in the 2-10 keV range with a flux density at 2 keV of 0.6 microJy. It has a flat (α_E_ = 0.62 +/- 0.25) power-law spectrum similar to type 1 Seyferts; Combined with Low Energy EXOSAT filter data and Einstein IPC observations, these data show that spectral curvature is…
Ultraviolet observations of AM Her.
Heise, J.; Verbunt, F.
Observations of AM Her at different flux levels obtained with IUE are presented. From the observations obtained at the lowest flux level, an upper limit to the white dwarf temperature of about 20,000 K, is derived, confirming an earlier temperature determination by Schmidt et al. (1981) from optical spectrophotometry. The increased flux levels at …
The Reionization of Unshocked Ejecta in SN 1006
Fesen, Robert A.; Hamilton, Andrew J. S.
The validity of carbon-deflagration models white dwarf models for type Ia supernovae is investigated by examining whether most of the iron in the center of SN 1006 exists in forms other than Fe II, such as iron grains or other ionic stages of iron, as the models require. The possible ways in which iron can be hidden in SN 1006 are reviewed, and an…
Far-ultraviolet absorption lines in active galaxies.
Ulrich, M. -H.
Attention is drawn to the far-ultraviolet absorption lines which have been discovered with IUE in a number of active nuclei. The properties of these lines are presented and discussed with emphasis on the following points: (i) the frequency of occurrence of far ultraviolet absorption lines (ii) a comparison between the properties of these lines and…
EXOSAT observations of variable coronal X-ray emission from the youngK dwarf AB Doradus (= HD 36705).
White, N. E.; Collier Cameron, A.; Bedford, D. K. +2 more
We present the results of a search for rotationally-modulated X-ray emission from the young KO dwarf AB Doradus, using the low- and medium-energy detectors on board the EXOSAT spacecraft. Two sets of observations were obtained, each covering all or nearly all of the 0.514 day rotation period of the star, in 1984 December and 1986 January. A single…
Optical polarimetry of P/Halley - Synthesis of the measurements in the continuum
Le Borgne, J. -F.; Bastien, P.; Levasseur-Regourd, A. C. +2 more
Ground-based observations of the linear polarization of P/Halley in the continuum by several independent groups of observers are analysed in common to produce synthetic polarization data. Curves of polarization as a function of phase angle are derived for the bright envelope around the nucleus, for the dust grains after they emerge from this envel…
Spectral energy distributions of galaxies in high-redshift clusters. III. Abell 370 at z=0.37.
Ellis, Richard S.; Couch, Warrick J.; MacLaren, Iain
We have imaged the distant cluster Abell 370 (z=0.37) with a CCD- based intermediate pass-band multicolour system defined in earlier papers in this series. Our technique is to use such colours to classify faint galaxies in redshift and spectral class without recourse to spectroscopic data. We demonstrate from a new comparison of ~80 spectra gather…
Atlas of wavelength dependence of ultraviolet extinction in the galaxy.
Greenberg, J. M.; Patriarchi, P.; Perinotto, M. +3 more
The paper presents a collection of 115 extinction curves derived from low dispersion IUE spectra. The spectra have been reduced with the use of techniques designed to reduce the effects of random noise and the influence of residual spectral features due to classification mismatch. The magnitudes of other instrumental and interpretational uncertain…
Long slit spectroscopy of emission line galaxies. I. The sample.
Durret, F.; Bergeron, J.
We present optical long slit spectroscopy for a sample of fifteen emission line galaxies with nuclei showing a sequence of activity levels in the radio, X-ray and/or optical ranges. They are presented in order of increasing activity in the optical range: LINERs, Seyfert 2s, obscured Seyfert 1s and Seyfert 1s. The existence of extended ionized enve…