Search Publications
Investigating ionized disc models of the variable narrow-line Seyfert 1 PG 1404+226
Brandt, W. N.; Fabian, A. C.; Boller, Th. +1 more
We investigate the use of relativistically blurred photoionized disc models on an XMM-Newton observation of the narrow-line Seyfert 1 galaxy PG 1404+226. The model is designed to reproduce the radiation from the inner accretion disc around a Kerr black hole, and is more successful at fitting the spectrum than models based on a thermal soft excess.…
CLASS B0631+519: last of the Cosmic Lens All-Sky Survey lenses
Pearson, T. J.; McKean, J. P.; Blandford, R. D. +13 more
We report on the discovery of the new gravitational lens system CLASS B0631+519. Imaging with the Very Large Array, the Multi-Element Radio-Linked Interferometer Network (MERLIN) and the Very Long Baseline Array (VLBA) reveals a doubly imaged flat-spectrum radio core, a doubly imaged steep-spectrum radio lobe and possible quadruply imaged emission…
Plasma diagnostics of active-region evolution and implications for coronal heating
Mathioudakis, M.; Bloomfield, D. S.; Keenan, F. P. +2 more
A detailed study is presented of the decaying solar-active region NOAA 10103 observed with the Coronal Diagnostic Spectrometer (CDS), the Michelson Doppler Imager (MDI) and the Extreme-ultraviolet Imaging Telescope (EIT) onboard the Solar and Heliospheric Observatory (SOHO). Electron-density maps formed using SiX (356.03 Å/347.41 Å) show that the …
HST and UKIRT imaging observations of z~ 1 6C radio galaxies - II. Galaxy morphologies and the alignment effect
Röttgering, H. J. A.; Inskip, K. J.; Best, P. N. +1 more
Powerful radio galaxies often display enhanced optical/ultraviolet emission regions, elongated and aligned with the radio jet axis. The aim of this series of papers is to investigate separately the effects of radio power and redshift on the alignment effect, together with other radio galaxy properties. In this second paper, we present a deeper ana…
85 Peg A: what age for a low-metallicity solar-like star?
Cardini, D.; D'Antona, F.; Montalbán, J. +3 more
We explore the possible evolutionary status of the primary component of the binary 85 Pegasi, listed as a target for asteroseismic observations by the MOST satellite. In spite of the assessed `subdwarf' status, and of the accurate distance determination from the Hipparcos data, the uncertainties in the metallicity and age, coupled with the uncerta…
The FERRUM project: experimentally determined metastable lifetimes and transition probabilities for forbidden [TiII] lines observed in η Carinae
Lundberg, H.; Johansson, S.; Hartman, H. +7 more
In the spectrum of an emission-line region ejected from the massive star Eta Carinae, called the strontium filament (SrF), forbidden lines from many elements, in particular [SrII] and [TiII], are observed. These lines are strong in this specific region and valuable for plasma diagnostics. Forbidden lines are not easily produced in laboratory light…
Astrophysical laser operating in the OI 8446-Åline in the Weigelt blobs of η Carinae
Johansson, S.; Letokhov, V. S.
Within the framework of a simple model of photophysical processes in the Weigelt blobs in the vicinity of the luminous blue variable (LBV) star η Carinae, we explain the presence of the fluorescent <OI> 8446-Åand forbidden [OI] 6300-Ålines as well as the absence of the allowed OI 7774-Åline in spectra recorded with the Hubble Space Telescope…
XMM spectroscopy of the transient supersoft source RXJ0513.9 - 6951: probing the dynamic white dwarf photosphere
Charles, P. A.; Heathcote, B.; McGowan, K. E. +3 more
The highly luminous (>1037ergs-1) supersoft X-ray sources (SSSs) are believed to be Eddington-limited accreting white dwarfs undergoing surface hydrogen burning. The current paradigm for SSSs involves thermally unstable mass transfer from a 1-2Msolar companion. However, this model has never been directly confirm…
The cool wake around 4C 34.16 as seen by XMM-Newton
Hardcastle, M. J.; Ponman, T. J.; Stevens, I. R. +3 more
We present XMM-Newton observations of the wake-radio galaxy system 4C 34.16, which shows a cool and dense wake trailing behind the host galaxy of 4C 34.16. A comparison with numerical simulations is enlightening, as they demonstrate that the wake is produced mainly by ram pressure stripping during the galactic motion through the surrounding cluste…
Noise characteristics of full-disc helioseismic observations made by resonant scattering spectrometers
Chaplin, W. J.; Elsworth, Y.; Isaak, G. R. +3 more
Resonant scattering spectrometers (RSSs) have been used to make high-precision full-disc helioseismic observations since the 1970s. They are capable of very high-precision determinations of line-shift, meaning that they are used to obtain precise velocity measurements, and, for suitably configured RSSs, the disc-averaged longitudinal magnetic fiel…