Search Publications
Detection of broad ultraviolet Fe II lines in the spectrum of NGC 1068.
Boksenberg, A.; Snijders, M. A. J.; Netzer, Hagai
Ultraviolet observations of the nucleus ofo NGC 1068, obtained by the IUE over a period of 5 yr, are combined to give a high signal-to-noise spectrum of this source. The ultraviolet stellar continuum, obtained by comparison with ground-based data, is subtracted to show the nuclear nonstellar component. The resulting spectrum shows clearly the pres…
Neutron star model atmospheres - a comparison with MXB 1728-34.
Fabian, A. C.; Ross, R. R.; Foster, A. J.
A detailed comparison between the X-ray spectra calculated for model atmospheres in neutron stars and the observed spectra of X-ray bursts is presented. Comptonization and free-free absorption and emission processes are taken into account, as are the effects of iron in its last three states of ionization. Two types of model are formulated, a const…
A unique triple-peaked type-1 X-ray burst from 4U/MXB 1636-53.
van Paradijs, J.; van der Klis, M.; Lewin, W. H. G. +3 more
The authors report the detection, with EXOSAT, of an X-ray burst from 4U/MXB 1636-53, whose intensity profile shows three distinct peaks. A time-resolved spectral analysis of this burst shows that this triple-peaked profile, which is clearly visible in the bolometric flux variations, is not the result of a major radius expansion of the neutron sta…
EXOSAT observations of the Seyfert galaxy NGC 7469; rapid hard X-rayvariability and a soft X-ray excess.
Barr, P.
The results of a series of EXOSAT observations of the Seyfert 1 (and starburst) galaxy NGC 7469 performed in July 1984 are presented. During one observation, hard X-ray variability by a factor 2 within 5 hr was found, while the soft X-ray intensity remained constant. In addition the spectral data indicate an excess of soft X-ray emission over that…
A multi-wavelength study of the long-period AM HER system E2003+225 -I. The soft X-ray light curve and overall energy spectrum.
Mukai, K.; Maraschi, L.; Chiappetti, L. +10 more
X-ray, UV and optical data are presented of the longest period AM Her object, E2003+225, from October 12, 1983, together with a new linear polarization ephemeris. The optical and X-ray data were obtained simultaneously and the UV observations were carried out on the same day. A 6-hr observation with the Exosat 500 line/mm objective grating restric…
An ultraviolet and optical study of the broad-line radio galaxy 3C 382.
Perez, E.; Fosbury, R. A. E.; Tadhunter, C. N.
Ultraviolet spectra covering 13 separate epochs are presented for the extreme broad-line radio galaxy 3C 382. These show marked variability in both lines and continuum on a time-scale less than about 1 yr. The C IV 1550 A and L-alpha 1216 A lines follow the changes in the ultraviolet continuum but appear to have different profiles, the L-alpha 121…
A multi-wavelength study of the long-period AM HER system E2003+225 -II. Changes in the accretion geometry.
Mukai, K.; Maraschi, L.; van Paradijs, J. +7 more
The longest period AM Her system E2003+225 was observed on 1984 July 24 with IUE, with simultaneous optical spectroscopy and photometry from La Palma. The variations of the overall continuum from 1200 to 5000 Å with orbital phase allow a study of the different spectral components in the system. High-resolution optical spectra show complex line pro…
A search for X-ray periodicities from 4U 1700-37.
Stella, L.; White, N. E.; Gottwald, M.
Using the EXOSAT observatory the authors have observed the massive X-ray binary system 4U 1700-37 for more than one complete orbital period. The authors report on a search for X-ray pulsations. No coherent periodicity was detected with upper limits to the pulsed fraction over the frequency range 256 to 2×10-5Hz (corresponding to rotatio…
PKS 2005-489 : a very bright BL Lac object in a nearby galaxy.
Wamsteker, W.; Warwick, R. S.; Pettini, M. +2 more
The galaxy identified with the flat-spectrum radio source PKS 2005-489 has a bright and variable stellar nucleus with a brightest observed V magnitude of ≡13. The authors report radio, optical, UV and X-ray observations which indicate variability and power-law continua in each of these wavebands, leading to the conclusion that PKS 2005-489 is one …
Ultraviolet spectra of quasars in the redshift interval 0.3 to 2.0.
Wilson, R.; Gondhalekar, P. M.; Obrien, P.
UV spectroscopic observations of nine QSOs with z = 0.3-2.0, obtained with the IUE SWP and LWR(P) instruments during 1978-1983, are reported. The continuum emission is attributed to the combination of a 20,000-30,000-K blackbody (the source of most of the UV emission), Balmer emission, and a power-law component (extending to the X-ray emission). T…