Search Publications
Discovery of a 0.42-s pulsar in the ultraluminous X-ray source NGC 7793 P13
Salvaterra, R.; Haberl, F.; Greiner, J. +11 more
NGC 7793 P13 is a variable (luminosity range ∼100) ultraluminous X-ray source proposed to host a stellar-mass black hole of less than 15 M⊙ in a binary system with orbital period of 64 d and a 18-23 M⊙ B9Ia companion. Within the EXTraS (Exploring the X-ray Transient and variable Sky) project, we discovered pulsations at a per…
Growing supermassive black holes in the late stages of galaxy mergers are heavily obscured
Sanders, D. B.; Harrison, F.; Stern, D. +10 more
Mergers of galaxies are thought to cause significant gas inflows to the inner parsecs, which can activate rapid accretion on to supermassive black holes (SMBHs), giving rise to active galactic nuclei (AGN). During a significant fraction of this process, SMBHs are predicted to be enshrouded by gas and dust. Studying 52 galactic nuclei in infrared-s…
A powerful flare from Sgr A* confirms the synchrotron nature of the X-ray emission
Genzel, R.; Hailey, C.; Harrison, F. +21 more
We present the first fully simultaneous fits to the near-infrared (NIR) and X-ray spectral slope (and its evolution) during a very bright flare from Sgr A*, the supermassive black hole at the Milky Way's centre. Our study arises from ambitious multiwavelength monitoring campaigns with XMM-Newton, NuSTAR and SINFONI. The average multiwavelength spe…
From ultraluminous X-ray sources to ultraluminous supersoft sources: NGC 55 ULX, the missing link
Fabian, A. C.; Pinto, C.; Soria, R. +8 more
In recent work with high-resolution reflection grating spectrometers (RGS) aboard XMM-Newton, Pinto et al. have discovered that two bright and archetypal ultraluminous X-ray sources (ULXs) have strong relativistic winds in agreement with theoretical predictions of high accretion rates. It has been proposed that such winds can become optically thic…
Strong XUV irradiation of the Earth-sized exoplanets orbiting the ultracool dwarf TRAPPIST-1
Wheatley, Peter J.; Gillon, Michaël; Louden, Tom +2 more
We present an XMM-Newton X-ray observation of TRAPPIST-1, which is an ultracool dwarf star recently discovered to host three transiting and temperate Earth-sized planets. We find the star is a relatively strong and variable coronal X-ray source with an X-ray luminosity similar to that of the quiet Sun, despite its much lower bolometric luminosity.…
BAT AGN Spectroscopic Survey (BASS) - VI. The ΓX-L/LEdd relation
Lamperti, Isabella; Schawinski, Kevin; Veilleux, Sylvain +11 more
We study the relation between accretion rate (in terms of L/LEdd) and shape of the hard X-ray spectral energy distribution (namely the photon index Γx) for a large sample of 228 hard X-ray-selected, low-redshift active galactic nuclei (AGNs), drawn from the Swift/BAT AGN Spectroscopic Survey (BASS). This includes 30 AGNs for …
The cool-core state of Planck SZ-selected clusters versus X-ray-selected samples: evidence for cool-core bias
Rossetti, M.; Molendi, S.; Gastaldello, F. +4 more
We characterized the population of galaxy clusters detected with the Sunyaev-Zeldovich (SZ) effect with Planck by measuring the cool-core state of the objects in a well-defined subsample of the Planck SZ catalogue. We used as an indicator the concentration parameter. The fraction of cool-core clusters is 29 ± 4 per cent and does not show significa…
A representative survey of the dynamics and energetics of FR II radio galaxies
Hardcastle, M. J.; Croston, J. H.; Ineson, J. +1 more
We report the first large, systematic study of the dynamics and energetics of a representative sample of Fanaroff-Riley type II (FR II) radio galaxies with well-characterized group/cluster environments. We used X-ray inverse-Compton and radio synchrotron measurements to determine the internal radio-lobe conditions, and these were compared with ext…
Optical, UV, and X-ray evidence for a 7-yr stellar cycle in Proxima Centauri
Drake, J. J.; Saar, S. H.; Kashyap, V. L. +2 more
Stars of stellar type later than about M3.5 are believed to be fully convective and therefore unable to support magnetic dynamos like the one that produces the 11-yr solar cycle. Because of their intrinsic faintness, very few late M stars have undergone long-term monitoring to test this prediction, which is critical to our understanding of magneti…
Observational constraints on the specific accretion-rate distribution of X-ray-selected AGNs
Georgakakis, A.; Salvato, M.; Schulze, A. +5 more
This paper estimates the specific accretion-rate distribution of AGNs using a sample of 4821 X-ray sources from both deep and shallow surveys. The specific accretion-rate distribution is used as a proxy of the Eddington ratio and is defined as the probability of a galaxy with a given stellar mass and redshift hosting an active nucleus with a certa…