Search Publications
Systematic uncertainties in the analysis of star cluster parameters based on broad-band imaging observations
Bastian, N.; de Grijs, R.; Anders, P. +5 more
High-resolution Hubble Space Telescope (HST) imaging observations of star cluster systems provide a very interesting and useful alternative to spectroscopic studies for stellar population analyses with 8-m class telescopes. Here, we assess the systematic uncertainties in (young) cluster age, mass and (to a lesser extent) extinction and metallicity…
What a local sample of spectroscopic binaries can tell us about the field binary population
Schröder, Klaus-Peter; Fisher, James; Smith, Robert Connon
We study a sample of spectroscopic binaries (SBs) in the local solar neighbourhood (d<= 100 pc and MV<= 4) in an attempt to find the distributions of the period, P, the primary mass, m1, and the mass ratio q(=m2/m1), as well as the initial mass function (IMF) of the local population of field binari…
The XMM-Newton/2dF Survey - VI. Clustering and bias of the soft X-ray point sources
Georgakakis, A.; Georgantopoulos, I.; Plionis, M. +1 more
We study the clustering properties of X-ray sources detected in the wide area (~2deg2) bright, contiguous XMM-Newton/2dF survey. We detect 432 objects to a flux limit of 5 × 10-15ergcm-2s-1 in the soft 0.5-2keV band. Performing the standard angular correlation function analysis, a ~3σ correlation signal …
Unusual X-ray transients in the Galactic Centre
Decourchelle, A.; Warwick, R. S.; Wang, Q. D. +1 more
We report the discovery in the Galactic Centre region of two hard X-ray sources, designated as XMM J174457-2850.3 and XMM J174544-2913.0, which exhibit flux variations in the 2-10 keV band in excess of a factor of 100 in observations spanning roughly a year. In both cases the observed hydrogen column density is consistent with a location near to t…
Wind-wind collision in the η Carinae binary system: a shell-like event near periastron
Falceta-Gonçalves, D.; Jatenco-Pereira, V.; Abraham, Z.
The exact nature of η Carinae is still an open issue. Strict periodicity in the light curves at several wavelengths seem to point to a binary system, but the observed radial velocities, measured from space with high spatial resolution, are in conflict with the ground-based observations used to calculate the binary orbit. Also, the observed 2-10 ke…
Optical and near-infrared integral field spectroscopy of the SCUBA galaxy N2 850.4
Ivison, R. J.; Smail, Ian; Swinbank, A. M. +7 more
We present optical and near-infrared integral field spectroscopy of the SCUBA galaxy SMMJ163650.43+405734.5 (ELAIS N2 850.4) at z= 2.385. We combine Lyα and Hα emission line maps and velocity structure with high-resolution HST ACS and NICMOS imaging to probe the complex dynamics of this vigorous starburst galaxy. The imaging data show a complex mo…
The Tully-Fisher relation of distant cluster galaxies
Milvang-Jensen, B.; Aragón-Salamanca, A.; Bamford, S. P. +1 more
We have measured maximum rotation velocities (Vrot) for a sample of 111 emission-line galaxies with 0.1 <~z<~ 1, observed in the fields of six clusters. From these data we construct `matched' samples of 58 field and 22 cluster galaxies, covering similar ranges in redshift (0.25 <=z<= 1.0) and luminosity (MB<=-1…
Optical and infrared signatures of ultra-luminous X-ray sources
Copperwheat, Christopher; Cropper, Mark; Soria, Roberto +1 more
We have constructed a model to describe the optical emission from ultra-luminous X-ray sources (ULXs). We assume a binary model with a black hole accreting matter from a Roche lobe filling companion star. We consider the effects of radiative transport and radiative equilibrium in the irradiated surfaces of both the star and a thin accretion disc. …
The dark lane of the planetary nebula NGC 6302*†
Waters, L. B. F. M.; Sahai, R.; Zijlstra, A. A. +4 more
The butterfly-shaped planetary nebula, NGC 6302, shows a unique, dense equatorial dark lane, which is presumably a dusty disc, obscuring an unobserved, very hot central star. We trace the structure of this disc using Hubble Space Telescope Hα and [N II] images, Very Large Telescope L-and M-band images at 0.4-arcsec resolution, including Brα and po…
A quantum electrodynamics model for non-thermal emission from soft gamma repeaters and anomalous X-ray pulsars
Hernquist, Lars; Heyl, Jeremy S.
Previously, we showed that, owing to effects arising from quantum electrodynamics (QED), magnetohydrodynamic fast modes of sufficient strength will break down to form electron-positron pairs while traversing the magnetospheres of strongly magnetized neutron stars. The bulk of the energy of the fast mode fuels the development of an electron-positro…