Search Publications
The first ultraviolet quasar-stacked spectrum at z ≃ 2.4 from WFC3
Vignali, C.; Lusso, E.; Prochaska, J. X. +4 more
The ionizing continuum from active galactic nuclei is fundamental for interpreting their broad emission lines and understanding their impact on the surrounding gas. Furthermore, it provides hints on how matter accretes on to supermassive black holes. Using Hubble Space Telescope's Wide Field Camera 3, we have constructed the first stacked ultravio…
Discovery of a 3.5 keV line in the Galactic Centre and a critical look at the origin of the line across astronomical targets
Profumo, Stefano; Jeltema, Tesla
We examine the claimed excess X-ray line emission near 3.5 keV including both a new analysis of XMM-Newton observations of the Milky Way centre and a reanalysis of the data on M 31 and clusters. In no case do we find conclusive evidence for an excess. In the case of the Galactic Centre, we show that known plasma lines, including in particular K XV…
A spectral-timing model for ULXs in the supercritical regime
Pintore, Fabio; Middleton, Matthew J.; Roberts, Timothy P. +2 more
Ultraluminous X-ray sources (ULXs) with luminosities lying between ∼3 × 1039 and 2 × 1040 erg s-1 represent a contentious sample of objects as their brightness, together with a lack of unambiguous mass estimates for the vast majority of the central objects, leads to a degenerate scenario where the accretor could be…
A tidal disruption flare in a massive galaxy? Implications for the fuelling mechanisms of nuclear black holes
Greiner, J.; Georgakakis, A.; Salvato, M. +6 more
We argue that the `changing look' active galactic nucleus (AGN) recently reported by LaMassa et al. could be a luminous flare produced by the tidal disruption of a supersolar mass star passing just a few gravitational radii outside the event horizon of a ∼108 M⊙ nuclear black hole. This flare occurred in a massive, star-formi…
Non-detection of X-ray emission from sterile neutrinos in stacked galaxy spectra
Bregman, Joel N.; Churazov, Eugene; Anderson, Michael E.
We conduct a comprehensive search for X-ray emission lines from sterile neutrino dark matter, motivated by recent claims of unidentified emission lines in the stacked X-ray spectra of galaxy clusters and the centres of the Milky Way and M31. Since the claimed emission lines lie around 3.5 keV, we focus on galaxies and galaxy groups (masking the ce…
Driving extreme variability: the evolving corona and evidence for jet launching in Markarian 335
Gallo, L. C.; Wilkins, D. R.
Variations in the X-ray emission from the narrow-line Seyfert 1 galaxy, Markarian 335, are studied on both long and short time-scales through observations made between 2006 and 2013 with XMM-Newton, Suzaku and NuSTAR. Changes in the geometry and energetics of the corona that give rise to this variability are inferred through measurements of the re…
The XMM-Newton view of the central degrees of the Milky Way
Haberl, F.; Nandra, K.; Ponti, G. +10 more
The deepest XMM-Newton mosaic map of the central 1.5 ° of the Galaxy is presented, including a total of about 1.5 Ms of EPIC-pn cleaned exposures in the central 15 arcsec and about 200 ks outside. This compendium presents broad-band X-ray continuum maps, soft X-ray intensity maps, a decomposition into spectral components and a comparison of the X-…
Diagnosing the accretion flow in ultraluminous X-ray sources using soft X-ray atomic features
Middleton, Matthew J.; Roberts, Timothy P.; Walton, Dominic J. +5 more
The lack of unambiguous detections of atomic features in the X-ray spectra of ultraluminous X-ray sources (ULXs) has proven a hindrance in diagnosing the nature of the accretion flow. The possible association of spectral residuals at soft energies with atomic features seen in absorption and/or emission and potentially broadened by velocity dispers…
The XMM Cluster Survey: testing chameleon gravity using the profiles of clusters
Hilton, Matt; Zhao, Gong-Bo; Stott, John P. +17 more
The chameleon gravity model postulates the existence of a scalar field that couples with matter to mediate a fifth force. If it exists, this fifth force would influence the hot X-ray emitting gas filling the potential wells of galaxy clusters. However, it would not influence the clusters weak lensing signal. Therefore, by comparing X-ray and weak …
X-ray coherent pulsations during a sub-luminous accretion disc state of the transitional millisecond pulsar XSS J12270-4859.
de Martino, D.; Torres, D. F.; Pellizzoni, A. +4 more
We present the first detection of X-ray coherent pulsations from the transitional millisecond pulsar XSS J12270-4859, while it was in a sub-luminous accretion disc state characterized by a 0.5-10 keV luminosity of 5 × 1033 erg s-1 (assuming a distance of 1.4 kpc). Pulsations were observed by XMM-Newton at an rms amplitude of …