Search Publications
The influence of gravitational lensing on the spectra of lensed quasi-stellar objects
Popović, L. Č.; Chartas, G.
We consider the influence of (milli/micro)lensing on the spectra of lensed quasi-stellar objects (QSOs). We propose a method for the observational detection of microlensing in the spectra of lensed QSOs and apply it to the spectra of three lensed QSOs (PG 1115+080, Q1413+117 and Q0957+561) observed with the Hubble Space Telescope. We find that the…
The X-ray source population of the globular cluster M15: Chandra high-resolution imaging
Charles, P. A.; Davies, M. B.; Naylor, T. +5 more
The globular cluster M15 was observed on three occasions with the High Resolution Camera on-board Chandra in 2001 in order to investigate the X-ray source population in the cluster centre. After subtraction of the two bright central sources, four faint sources were identified within 50 arcsec of the core. One of these sources is probably the plane…
Heavy element abundances in DAO white dwarfs measured from FUSE data
Barstow, M. A.; Holberg, J. B.; Hubeny, I. +3 more
We present heavy element abundance measurements for 16 DAO white dwarfs, determined from Far-Ultraviolet Spectroscopic Explorer (FUSE) spectra. Evidence of absorption by heavy elements was found in the spectra of all the objects. Measurements were made using models that adopted the temperatures, gravities and helium abundances determined from both…
The dynamics of velocity fluctuations in the solar wind - I. Coronal mass ejections
Raga, A. C.; Lara, A.; de Gouveia Dal Pino, E. M. +3 more
In this paper we present a simple, analytic model for the dynamical evolution of supersonic velocity fluctuations at the base of the ambient solar wind. These fluctuations result in the formation of dense working surfaces that travel down the wind. It is shown how the initial parameters of the fluctuations (velocity, density and duration) are rela…
The dark halo of the main lens galaxy in QSO 0957 + 561
Gil-Merino, R.; Goicoechea, L. J.; Ullán, A.
We present an analysis of infrared/optical/ultraviolet spectra of the two images of the first gravitationally lensed quasar Q0957 + 561A,B. The Hubble Space Telescope observations of Q0957 + 561A and Q0957 + 561B are separated in time by the known time delay in this system, so we can directly deduce the flux ratios. These flux ratios of images lea…
An XMM-Newton view of M101 - II. Global X-ray source properties
Warwick, R. S.; Roberts, T. P.; Ward, M. J. +2 more
We present the global X-ray properties of the point source population in the grand-design spiral galaxy M101, as seen with XMM-Newton. 108 X-ray sources are detected within the D25 ellipse of M101, of which ~24 are estimated to be background galaxies. Multiwavelength cross-correlations show that 20 sources are coincident with HII region…
XMM observations of the high-redshift quasar RXJ1028.6 - 0844 at z= 4.276: soft X-ray spectral flattening
Fabian, A. C.; Matsuoka, M.; Celotti, A. +2 more
We present results from a new XMM-Newton observation of the high-redshift quasar RXJ1028.6 - 0844 at a redshift of 4.276. The soft X-ray spectral flattening, as reported by a previous study with ASCA, is confirmed to be present, with, however, a reduced column density when modelled by absorption. The inferred column density for absorption intrinsi…
OH megamasers, starburst and AGN activity in Markarian 231
Knapen, J. H.; Richards, A. M. S.; Gray, M. D. +5 more
We present Multi-Element Radio-Linked Interferometer Network (MERLIN) observations of OH maser and radio continuum emission within a few hundred pc of the core of the ultraluminous infrared galaxy (ULIRG) Markarian 231. This is the only known OH megamaser galaxy classed as a Seyfert 1. Maser emission is identified with the 1665- and 1667-MHz trans…
Overtones of silicate and aluminate minerals and the 5-8 µm ice bands of deeply embedded objects
Hofmeister, A. M.; Bowey, J. E.
The distinct patterns, relatively low intensities and peak positions of overtone-combination bands of silicates and oxides suggest that the 5-8 µm spectral region can provide clues for the dust composition when near optically thick conditions exist for the 10-µm silicate feature. We present 1000-2500 cm-1 room-temperature la…
Luminosity segregation in three clusters of galaxies (A119, A2443, A2218)
Driver, Simon P.; De Propris, Roberto; Nulsen, Paul E. J. +2 more
We use deep wide-field V-band imaging obtained with the Wide Field Camera at the prime focus of the Issac Newton Telescope to study the spatial and luminosity distribution of galaxies in three low redshift (0.04 < z < 0.2) clusters: Abell 119, Abell 2443 and Abell 2218. The absolute magnitude limits probed in these clusters are MV…