Search Publications
Towards an understanding of the Of?p star HD191612: phase-resolved multiwavelength observations
Walborn, Nolan R.; Nazé, Yaël; Howarth, Ian D. +2 more
We present the analysis of phase-resolved X-ray and optical observations of the peculiar hot star HD191612 (Of?p). This star is known to display line-profile variations that are recurrent with a period of 538d and its spectrum was found to present the signature of a magnetic field. In the X-rays, it is slightly overluminous compared to the canonic…
VLT/near-infrared integral field spectrometer observations of molecular hydrogen lines in the knots of the planetary nebula NGC 7293 (the Helix Nebula)
Smith, M. D.; Zijlstra, A. A.; Lowe, K. T. E. +6 more
Knots are commonly found in nearby planetary nebulae (PNe) and star-forming regions. Within PNe, knots are often found to be associated with the brightest parts of the nebulae and understanding the physics involved in knots may reveal the processes dominating in PNe. As one of the closest PNe, the Helix Nebula (NGC 7293) is an ideal target to stud…
Colliding stellar wind models with non-equilibrium ionization: X-rays from WR 147
Zhekov, Svetozar A.
The effects of non-equilibrium ionization are explicitly taken into account in a numerical model which describes colliding stellar winds (CSW) in massive binary systems. This new model is used to analyse the most recent X-ray spectra of the WR+OB binary system WR 147. The basic result is that it can adequately reproduce the observed X-ray emission…
On the relativistic iron line and soft excess in the Seyfert 1 galaxy Markarian 335
O'Neill, Paul M.; Nandra, Kirpal; Cappi, Massimo +2 more
We report a 133-ks XMM-Newton observation of the Seyfert 1 galaxy Markarian 335. The 0.4-12 keV spectrum contains an underlying power-law continuum, a soft excess below 2 keV, and a double-peaked iron emission feature in the 6-7 keV range. We investigate the possibility that the double-peaked emission might represent the characteristic signature o…
Structural parameters of Mayall II = G1 in M31
Wu, H.; Wu, J.; Chen, J. +8 more
Mayall II = G1 is one of the most luminous globular clusters (GCs) known in M31. New deep, high-resolution observations with the Advanced Camera for Surveys on the Hubble Space Telescope are used to provide accurate photometric data to the smallest radii yet. In particular, we present the precise variation of ellipticity and position angle, and of…
The young star cluster system in the Antennae: evidence for a turnover in the luminosity function
de Grijs, R.; Anders, P.; Fritze-v. Alvensleben, U. +2 more
The luminosity functions (LFs) of star cluster (SC) systems (i.e. the number of clusters per luminosity interval) are vital diagnostics to probe the conditions of SC formation. Early studies have revealed a clear dichotomy between old globular clusters and young clusters, with the former characterized by Gaussian-shaped LFs, and the latter followi…
Spectroscopic follow-up of a cluster candidate at z = 1.45
Simpson, Chris; Rawlings, Steve; Jarvis, Matt +7 more
We have obtained deep optical spectroscopic data of the highest-redshift cluster candidate (z ~ 1.4, CVB13) selected by Van Breukelen et al. in a photometric optical/infrared catalogue of the Subaru XMM-Newton Deep Field. The data, which comprise 104 targeted galaxies, were taken with the DEep Imaging Multi-Object Spectrograph on the Keck 2 telesc…
Long-term infrared variability of the UX Ori-type star SV Cep
Prusti, T.; Ábrahám, P.; Dullemond, C. P. +1 more
We investigate the long-term optical-infrared variability of SVCep and explain it in the context of an existing UX Ori (UXOR) model. A 25-month monitoring programme was completed with the Infrared Space Observatory in the 3.3-100 µm wavelength range. Following a careful data reduction, the infrared light curves were correlated with the varia…
A study of the Sunyaev-Zel'dovich increment using archival SCUBA data
Halpern, Mark; Scott, Douglas; Zemcov, Michael +2 more
In a search for evidence of the short wavelength increment in the Sunyaev-Zel'dovich (SZ) effect, we have analysed archival galaxy cluster data from the Submillimetre Common User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope, resulting in the most complete pointed survey of clusters at 850µm to date. SCUBA's 850-µm passb…
A longer XMM-Newton look at IZwicky1: physical conditions and variability of the ionized absorbers
Brandt, W. N.; Costantini, E.; Fabian, A. C. +2 more
We present a spectral analysis of the narrow-line Seyfert 1 galaxy IZwicky1, focusing on the characteristics of the ionized absorbers as observed with XMM-Newton in 2005. The soft X-ray spectrum shows absorption by two components of ionized gas with a similar column density (NH ~ 1021cm-2) and ionization parameters…