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Examining the Physical Conditions of a Warm Corona in Active Galactic Nuclei Accretion Discs
D. R. Ballantyne
A warm corona at the surface of an accretion disc has been proposed as a potential location for producing the soft excess commonly observed in the X-ray spectra of active galactic…
An evolving broad iron line from the first Galactic ultraluminous X-ray pulsar Swift J0243.6+6124
Gaurava K. Jaisawal, Colleen A. Wilson-Hodge, Andrew C. Fabian +15
We present a spectral study of the ultraluminous Be/X-ray transient pulsar Swift J0243.6+6124 using Neutron Star Interior Composition Explorer (NICER) observations during the syste…
A NICER thermonuclear burst from the millisecond X-ray pulsar SAX J1808.4-3658
Peter Bult, Gaurava K. Jaisawal, Tolga Güver +9
The Neutron Star Interior Composition Explorer (NICER) has extensively monitored the August 2019 outburst of the 401 Hz millisecond X-ray pulsar SAX J1808.4-3658. In this Letter, w…
The evolving X-ray spectrum of active galactic nuclei: evidence for an increasing reflection fraction with redshift
M. S. Avirett-Mackenzie, D. R. Ballantyne
The cosmic X-ray background (XRB) spectrum and active galaxy number counts encode essential information about the spectral evolution of active galactic nuclei (AGNs) and have been…
Probing the Black Hole Engine with Measurements of the Relativistic X-ray Reflection Component
Javier A. García, Matteo Bachetti, David R. Ballantyne +21
Over the last decades X-ray spectroscopy has proven to be a powerful tool for the estimation of black hole spin and several other key parameters in dozens of AGN and black hole X-r…
The stellar remnants of high redshift nuclear starburst discs: a potential origin for nuclear star clusters?
R. Gohil, D. R. Ballantyne, G. Li
Nuclear starburst discs (NSDs) are very compact star-forming regions in the centers of galaxies that have been studied as a possible origin for the absorbing gas around a central a…