Search Publications
Collisional interaction limits between dark matter particles and baryons in `cooling flow' clusters
Hu, Jian; Lou, Yu-Qing
Presuming weak collisional interactions to exchange the kinetic energy between dark matter and baryonic matter in a galaxy cluster, we re-examine the effectiveness of this process in several `cooling flow' galaxy clusters using available X-ray observations and infer an upper limit on the heavy dark matter particle (DMP)-proton cross-section σ…
Properties of X-ray-selected broad absorption-line quasars
Page, M. J.; Seymour, N.; Kennea, J. A. +6 more
Broad absorption-line quasars (commonly termed BALQSOs) contain the most dramatic examples of active galactic nucleus (AGN) driven winds. The high absorbing columns in these winds, ~1024cm-2, ensure that BALQSOs are generally X-ray faint. This high X-ray absorption means that almost all BALQSOs have been discovered through op…
IRAS22036+5306: an Al2O3 oxide-dominated post-AGB star
Maldoni, M. M.; Ireland, T. R.; Robinson, G.
Radiative transfer modelling of the Infrared Space Observatory (ISO) spectrum of IRAS22036+5306 has shown that its unusual 11-µm band can be suitably modelled with an alumina-olivine mixture substantially dominated by the former. The results of this work add further credence to recent findings that significant amounts of Al2O…
The early-type semidetached binary system V716 Centaurus
Demircan, O.; Bakış, V.; Eker, Z. +1 more
New high-resolution spectra of V716 Cen revealed for the first time lines of the secondary component and its radial velocities. The simultaneous solution of the new radial velocity curves and the Hipparcos light curve yield the reliable absolute dimensions of this semidetached system. The masses for the primary and secondary are M1 = 5.…
The stellar populations of M33's outer regions - IV. Inflow history and chemical evolution
Sarajedini, A.; Barker, Michael K.
We have modelled the observed colour-magnitude diagram (CMD) at one location in M33's outskirts under the framework of a simple chemical evolution scenario which adopts instantaneous and delayed recycling for the nucleosynthetic products of Type II and Ia supernovae. In this scenario, interstellar gas forms stars at a rate modulated by the Kennicu…
Constraints on the average magnetic field strength of relic radio sources 0917+75 and 1401-33 from XMM-Newton observations
Harrison, Fiona A.; Harris, D. E.; Mao, Peter H. +1 more
We observed two relic radio sources, 0917+75 and 1401-33, with the XMM-Newton X-ray observatory. We did not detect any X-ray emission, thermal or non-thermal, in excess of the local background level from either target. This imposes new upper limits on the X-ray flux due to inverse Compton scattering of photons from the cosmic microwave background …
On the peculiar properties of the narrow-line quasar PG 1543+489
Bianchi, Stefano; Piconcelli, Enrico; Vignali, Cristian +1 more
We present the analysis of four XMM-Newton observations of the narrow-line quasar PG 1543+489 at z = 0.400 carried out over a rest-frame time-scale of about 3 yr. The X-ray spectrum is characterized by a broad, relativistic iron Kα emission line and a steep photon index, which can be both explained by a ionized reflection model, where the source o…
Young globular clusters in an old S0: clues to the formation history of NGC 4570
Anders, P.; Kotulla, R.; Fritze, U.
We here present our first attempt to use globular clusters as tracers of their parent galaxy's formation history. Globular cluster systems of most early-type galaxies feature two peaks in their optical colour distributions. Blue-peak globular clusters are generally believed to be old and metal-poor. The ages, metallicities, and the origin of the r…
Probing the nature of IGR J16493-4348: spectral and temporal analysis of the 1-100 keV emission
de Rosa, A.; Hill, A. B.; Bird, A. J. +5 more
IGR J16493-4348 was one of the first new sources to be detected by the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) γ-ray telescope in the 18-100 keV energy band. Based on spatial coincidence, the source was originally associated with the free radio pulsar PSR J1649-4349. Presented here are the results of 2.8 Ms of observations made …
The angular separation of the components of the Cepheid AWPer
Massa, D.; Evans, N. R.
The 6.4d classical Cepheid AWPer is a spectroscopic binary with a period of 40yr. Analysing the centroids of Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS) spectra obtained in 2001 November, we have determined the angular separation of the binary system. Although we currently have spatially resolved data for a single epoch …