Search Publications
Exploring the nature of the brightest hyper-luminous X-ray source
Maccarone, T. J.; Heywood, I.; Farrell, S. A. +7 more
The small subset of hyper-luminous X-ray sources with luminosities in excess of ∼1041 erg s-1 are hard to explain without the presence of an intermediate mass black hole, as significantly super-Eddington accretion and/or very small beaming angles are required. The recent discovery of HLX-1, the most luminous object in this cl…
Unlocking the nature of ultraluminous X-ray sources using their X-ray spectra
Done, C.; Roberts, T. P.; Gladstone, J. C.
We explore the nature of ultraluminous X-ray sources through detailed investigations of their spectral shape using some of the highest quality data available in the XMM-Newton public archives. Phenomenological models allow us to characterise their spectra, while more 'physically-motivated' models enable us to explore the physical processes underly…
Accretion, jets and winds: High-energy emission from young stellar objects
Günther, H. M.
This article summarizes the processes of high-energy emission in young stellar objects. Stars of spectral type A and B are called Herbig Ae/Be (HAeBe) stars in this stage, all later spectral types are termed classical T Tauri stars (CTTS). Both types are studied by high-resolution X-ray and UV spectroscopy and modeling. Three mechanisms contribute…
Water in star-forming regions with Herschel
van Dishoeck, E. F.; Kristensen, L. E.
The Herschel Space Observatory is well suited to address several important questions in star- and planet formation, as is evident from its first year of operation. This paper focuses on observations of water, a key molecule in the physics and chemistry of star-formation. In the WISH Key Program, a comprehensive set of water lines is being obtained…
A 2007 photometric study and UV spectral analysis of the Wolf-Rayet binary V444 Cyg
Ekmekçi, F.; Eriş, F. Z.
Photometric and spectroscopic characteristics of the WN5+O6 binary system, V444 Cyg, were studied. The Wilson-Devinney (WD) analysis, using new BV observations carried out at the Ankara University Observatory, revealed the masses, radii, and temperatures of the components of the system as MWR=10.64 M⊙, MO=24.68 M
Six years of XMM-Newton observations of NGC 1313 X-1 and X-2
Pintore, F.; Zampieri, L.
We present a systematic analysis of the X-ray spectra of NGC 1313 X-1 and NGC 1313 X-2, using six years of XMM-Newton observations (17 observations). We fitted the continuum with a Comptonization model plus a multicolor blackbody disc, that describes the effects of an accretion disc plus an optically thick corona. We checked the consistency of thi…
Optical variability of the ultraluminous X-ray source NGC 1313 X-2
Falomo, R.; Soria, R.; Zampieri, L. +2 more
We analyzed the longest phase-connected photometric dataset available for NGC 1313 X-2, looking for the ∼6 day modulation reported by Liu et al. (2009). The folded B-band light curve shows a 6 days periodicity with a significance slightly larger than 3σ. The low statistical significance of this modulation, along with the lack of detection in the V…
Key results from an XMM-Newton and Chandra study of a new sample of extreme ULXs from the 2XMM catalogue
Roberts, T. P.; Walton, D. J.; Sutton, A. D.
We present highlights from a study of a sample of 10 extreme-luminosity candidate ultraluminous X-ray sources (L_X>5 × 1040 erg s-1), all at distances <100 Mpc, identified from a cross-correlation of the RC3 catalogue of galaxies with the 2XMM catalogue. Five of the sample have also been observed by Chandra. Of the 10 s…
A large catalogue of ultraluminous X-ray source candidates in nearby galaxies
Roberts, T. P.; Walton, D. J.; Gladstone, J. C. +1 more
Since their discovery, Ultraluminous X-ray sources (ULXs) have attracted attention due to their combination of extreme luminosities and extra-nuclear locations. However, they are a fairly rare phenomenon, and attempts to investigate the general properties of the population have been hindered by a relative lack of known sources. Here, we present a …
Does NGC 5408 X-1 really contain an intermediate-mass black hole?
Done, C.; Roberts, T. P.; Middleton, M. J. +1 more
NGC 5408 X-1 is one of only a handful of ultraluminous X-ray sources (ULXs) to demonstrate a strong quasi-periodic oscillation (QPO) in its lightcurve. This has been interpreted as being analogous to the type C low-frequency QPO seen in black hole binaries (BHBs) when accreting at sub-Eddington rates, implying an intermediate-mass black hole (IMBH…