Search Publications
Hysteresis in broad-line regions of active galactic nuclei.
van Groningen, E.; Wanders, I.; Perry, J. J.
The response of emission-line luminosities to changes in the observed continuum in active galaxies is commonly used for reverberation mapping (RM) of the emission-line region. The method assumes regularity in the continuum source and linearity in the line response to the continuum, and that the phase-space distribution of the line-emitting gas is …
Time variability in the UV resonance lines of the cataclysmic variables MU Cen, AH HER and QU Car.
Knigge, C.; Drew, J. E.; Hoare, M. G. +1 more
We present a time-variability study of the uV resonance lines Nv 1240, Si iv 1397 and C iv 1549 in the dwarf novae AH Her and MU Cen and the nova-like variable QU Car. The main findings are as follows. (i)Virtually no variation can be seen in our data for MU Cen. (ii) AH Her shows velocity shifting of its resonance lines, with semi-amplitudes rang…
Ultraviolet and Radio Observations of the Young Rapidly Rotating k0 Dwarf Star HD197890
Carpenter, K. G.; Robinson, R. D.; Slee, O. B. +2 more
We present the results of UV observations taken with the International Ultraviolet Explorer (IUE) satellite and microwave observations obtained with the Australia Telescope during an observing campaign of the rapidly rotating K0 dwarf star III) 197890, nicknamed `Speedy Mic'. This star was recently recognized as a powerful, transient EUV source by…
Detection of episodic mass outflow in the newly discovered hot DO white dwarf RE 0503-289.
Barstow, M. A.; Sion, E. M.
We report the unexpected detection of variable mass outflow from the very hot (Teff =70000 K), He-rich DOZ1 degenerate RE 0503-289. This detection is based upon our analysis of absorption-line core strength variations and blueward asymmetries in two lUE echelle high-dispersion images obtained 13 months apart. The oufflow has a terminal velocity of…
Classification of the HIPPARCOS Input Catalogue Using the Kohonen Network
Hernandez-Pajares, M.; Floris, J.
The unsupervised classification with respect to stellar populations of 106 000 of the 118 000 Hipparcos input catalogue stars is presented, in terms of angular position and velocity, apparent magnitude and spectral type. The classification is performed first by merging the real data with a small sample of synthetic stars, which are representative …
An unusual high-redshift object discovered with the Hubble Space Telescope : peculiar starburst galaxy or new gravitational lens?
Glazebrook, K.; Griffiths, R.; Ellis, R. +2 more
We report the discovery of an object with a very peculiar structure, using observations from the refurbished Hubble Space Telescope (HST) as part of the Medium-Deep Survey project. The object includes four compact blue components arranged around an extended red component, with mutual separations of <1 arcsec. Using a ground-based spectrum as an…
3 Puppis : a peculiar object with infrared excess.
Rovero, Adrian C.; Ringuelet, Adela E.
We present a model that accounts for the UV, photographic, and IR observations of 3 Puppis. The model consists of a binary system in which the primary is an A supergiant with a mild chromosphere; the primary fills its Roche lobe. The velocity law in the extended atmosphere, which is responsible for the density distribution of the gas, and a chromo…
Optical and UV spectroscopy towards stars in the direction of the Cohen high-velocity H I stream.
Dufton, P. L.; Keenan, F. P.; Bates, B. +2 more
We present high-resolution, high signal-to-noise ratio optical spectra and UV spectra obtained with lUE for several stars that lie within and adjacent to the Cohen high- velocity (Hv) stream, which is considered by Cohen to lie within 300 pc. From spectral classifications, published photometry and LTE model atmosphere analysis of our stellar spect…
A non-thermal radio/optical/X-ray source in PKS 2316-423.
Fabian, A. C.; Crawford, C. S.
We report observations of PKS 2316-423 in the ultraviolet and with the ROSAT HRI, where it appears as a bright point source. Optical spectroscopy reveals weak emission lines and a strong, excess blue continuum that is centrally concentrated. The combined optical- ultraviolet continuum spectrum cannot be fitted by any simple combination of a main-s…
Pulsational Activity on Ik-Pegasi
Kellett, B. J.; Lloyd, C.; Smalley, B. +1 more
High-time-resolution photometry of millimagnitude precision using the Fine Error Sensor on board the International Ultraviolet Explorer is presented. A few hours of data, when subjected to an optimal (Bayesian) analysis, reveal two pulsational frequencies in the star 1K Peg A, one of which was not previously known. A fit to the empirical P-L-C rel…