Search Publications
Phase models of the Milky Way stellar disc
Orlov, V. V.; Rodionov, S. A.
We present a new iterative method for constructing equilibrium phase models of stellar systems. Importantly, this method can provide phase models with arbitrary mass distributions. The method is based on the following principle. Our task is to generate an equilibrium N-body system with a given mass distribution. For this purpose, we let the system…
Puzzling X-rays from the new colliding wind binary Wolf-Rayet 65 (WC9d)
Hamann, W. -R.; Oskinova, L. M.
We report the discovery of variability in the X-ray emission from the Wolf-Rayet type star WR65. Using archival Chandra data spanning over 5yr, we detect changes of the X-ray flux by a factor of 3 accompanied by changes in the X-ray spectra. We believe that this X-ray emission originates from wind-wind collision in a massive binary system. The obs…
ATCA observations of the very young Planetary Nebula SAO 244567
Umana, G.; Trigilio, C.; Leto, P. +2 more
The radio emission from the youngest known Planetary Nebula, SAO244567, has been mapped at 1384, 2368, 4800, 8640, 16832 and 18752 MHz by using the Australian Telescope Compact Array (ATCA). These observations constitute the first detailed radio study of this very interesting object, as they allow us to obtain the overall radio morphology of the s…
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…