Search Publications
What controls the CIV line profile in active galactic nuclei?
Laor, Ari; Baskin, Alexei
The high-ionization lines in active galactic nuclei (AGN), such as CIV, tend to be blueshifted with respect to the lower-ionization lines, such as Hβ, and often show a strong blue excess asymmetry not seen in the low-ionization lines. There is accumulating evidence that the Hβ profile is dominated by gravity, and thus provides a useful estimate of…
The abundance discrepancy - recombination line versus forbidden line abundances for a northern sample of galactic planetary nebulae
Barlow, M. J.; Liu, X. -W.; Wesson, R.
We present deep optical spectra of 23 galactic planetary nebulae, which are analysed in conjunction with archival infrared and ultraviolet spectra. We derive nebular electron temperatures based on standard collisionally excited line (CEL) diagnostics as well as the hydrogen Balmer jump and find that, as expected, the Balmer jump almost always yiel…
Constraints on the ionizing flux emitted by T Tauri stars
Clarke, C. J.; Pringle, J. E.; Alexander, R. D.
We present the results of an analysis of ultraviolet observations of T Tauri stars (TTs). By analysing emission measures taken from the literature, we derive rates of ionizing photons from the chromospheres of five classical TTs in the range ~1041-1044 photon s-1, although these values are subject to large uncertai…
Hubble Space Telescope ultraviolet spectroscopy of blazars: emission-line properties and black hole masses
Pian, E.; Falomo, R.; Treves, A.
The ultraviolet (UV) spectra of 16 blazars (<z>~= 1) from the archives of the Hubble Space Telescope Faint Object Spectrograph have been analysed in order to study in a systematic way the properties of their broad UV emission lines. We find that the luminosities of the most prominent and intense lines, Lyα and CIVλ1549, are similar to those …
A study of two post-common envelope binary systems
Maxted, P. F. L.; Exter, K. M.; Napiwotzki, R. +2 more
We present intermediate-resolution, phase-resolved spectra of the close-binary systems EC 11575-1845 and V664 Cas, the central star of the planetary nebula HFG 1. Both systems have a very rich emission-line spectrum originating from the face of the cool star, which is irradiated by the hot subdwarf star. The HI emission lines are wide, consistent …
Infrared mergers and infrared quasi-stellar objects with galactic winds - III. Mrk 231: an exploding young quasi-stellar object with composite outflow/broad absorption lines (and multiple expanding superbubbles)
Zheng, W.; Terlevich, R.; Lípari, S. +3 more
We present a study of outflow (OF) and broad absorption line (BAL) systems in Mrk 231, and in similar infrared (IR) quasi-stellar objects (QSOs). This study is based mainly on one-dimensional and two-dimensional spectroscopy (obtained at La Palma/William Herschel Telescope, Hubble Space Telescope, International Ultraviolet Explorer, European South…
Correlation patterns between 11 diffuse interstellar bands and ultraviolet extinction
Krełowski, J.; Megier, A.; Weselak, T.
We relate the equivalent widths of 11 diffuse interstellar bands, measured in the spectra of 49 stars, to different colour excesses in the ultraviolet. We find that most of the observed bands correlate positively with the extinction in the neighbourhood of the 2175-Åbump. Correlation with colour excesses in other parts of the extinction curve is m…
Outflowing material in the compact steep-spectrum source quasar 3C 48: evidence of jet-cloud interaction?
Saikia, D. J.; Srianand, R.; Gupta, Neeraj
We report on the detection of a zabs= 0.3654 associated absorption-line system in the ultraviolet spectrum of the compact steep-spectrum source (CSS) quasar 3C 48. The absorbing material is blueshifted with respect to the quasar emission-line redshift, zem= 0.3700, suggesting an outflow velocity of ~1000 km s-1. We…
The chemical composition of δ Scuti⋆
Kovtyukh, V.; Soubiran, C.; Kim, Chulhee +4 more
We present chemical abundances in the photosphere of δ Scuti (δ Sct) - a prototype of the class of pulsating variables - determined from the analysis of a spectrum obtained by using the 2-m telescope at the Peak Terskol Observatory and a high-resolution spectrometer with R= 52 000, a signal-to-noise ratio 250 and from International Ultraviolet Exp…