Search Publications
The role of the reflection fraction in constraining black hole spin.
Fabian, A. C.; Dauser, T.; Wilms, J. +2 more
In many active galaxies, the X-ray reflection features from the innermost regions of the accretion disc are relativistically distorted. This distortion allows us to measure parameters of the black hole such as its spin. The ratio in flux between the direct and the reflected radiation, the so-called reflection fraction, is determined directly from …
The incidence of obscuration in active galactic nuclei
Berta, S.; Magnelli, B.; Lutz, D. +22 more
We study the incidence of nuclear obscuration on a complete sample of 1310 active galactic nuclei (AGN) selected on the basis of their rest-frame 2-10 keV X-ray flux from the XMM-COSMOS survey, in the redshift range 0.3 < z < 3.5. We classify the AGN as obscured or unobscured on the basis of either the optical spectral properties and the ove…
A state change in the low-mass X-ray binary XSS J12270-4859
Edwards, P. G.; Corbel, S.; Bassa, C. G. +10 more
Millisecond radio pulsars acquire their rapid rotation rates through mass and angular momentum transfer in a low-mass X-ray binary system. Recent studies of PSR J1824-2452I and PSR J1023+0038 have observationally demonstrated this link, and they have also shown that such systems can repeatedly transition back-and-forth between the radio millisecon…
Ultrafast outflows in radio-loud active galactic nuclei
Cappi, M.; Guainazzi, M.; Tombesi, F. +5 more
Recent X-ray observations show absorbing winds with velocities up to mildly relativistic values of the order of ∼0.1c in a limited sample of six broad-line radio galaxies. They are observed as blueshifted Fe XXV-XXVI K-shell absorption lines, similarly to the ultrafast outflows (UFOs) reported in Seyferts and quasars. In this work we extend the se…
Warm absorbers in X-rays (WAX), a comprehensive high-resolution grating spectral study of a sample of Seyfert galaxies - I. A global view and frequency of occurrence of warm absorbers.
Dewangan, Gulab C.; Guainazzi, Matteo; Laha, Sibasish +2 more
We present results from a homogeneous analysis of the broad-band 0.3-10 keV CCD resolution as well as of the soft X-ray high-resolution grating spectra of a hard X-ray flux-limited sample of 26 Seyfert galaxies observed with XMM-Newton. Our goal is to characterize warm absorbers (WAs) along the line of sight to the active nucleus. We significantly…
General relativistic modelling of the negative reverberation X-ray time delays in AGN
Papadakis, I. E.; Emmanoulopoulos, D.; Dovčiak, M. +1 more
We present the first systematic physical modelling of the time-lag spectra between the soft (0.3-1 keV) and the hard (1.5-4 keV) X-ray energy bands, as a function of Fourier frequency, in a sample of 12 active galactic nuclei which have been observed by XMM-Newton. We concentrate particularly on the negative X-ray time-lags (typically seen above 1…
Improved mass and radius constraints for quiescent neutron stars in ω Cen and NGC 6397
Campana, S.; Heinke, C. O.; Cohn, H. N. +8 more
We use Chandra and XMM-Newton observations of the globular clusters ω Cen and NGC 6397 to measure the spectrum of their quiescent neutron stars (NSs), and thus to constrain the allowed ranges of mass and radius for each. We also use Hubble Space Telescope photometry of NGC 6397 to identify a potential optical companion to the quiescent NS, and fin…
An X-ray survey of the 2 Jy sample - I. Is there an accretion mode dichotomy in radio-loud AGN?
Hardcastle, M. J.; Croston, J. H.; Morganti, R. +4 more
We carry out a systematic study of the X-ray emission from the active nuclei of the 0.02 < z < 0.7 2 Jy sample, using Chandra and XMM-Newton observations. We combine our results with those from mid-infrared, optical emission-line and radio observations, and add them to those of the 3CRR sources. We show that the low-excitation objects in our…
A volume-limited sample of X-ray galaxy groups and clusters - I. Radial entropy and cooling time profiles
Fabian, A. C.; Sanders, J. S.; Panagoulia, E. K.
We present the first results of our study of a sample of 101 X-ray galaxy groups and clusters, which is volume-limited in each of three X-ray luminosity bins. The aim of this work is to study the properties of the innermost ICM in the cores of our groups and clusters, and to determine the effect of non-gravitational processes, such as active galac…
On the determination of the spin and disc truncation of accreting black holes using X-ray reflection
Fabian, A. C.; Miller, J. M.; Reynolds, C. S. +4 more
We discuss the application of simple relativistically blurred X-ray reflection models to the determination of the spin and the inner radius of the disc in accreting black holes. Observationally, the nature of the corona is uncertain a priori, but a robust determination of the inner disc radius can be made when the disc emissivity index is tightly …