246 citations · 2.5k across the 59 of their papers we have counts for
59 papers
Persistence of the Millihertz X-ray Quasi-Periodic Oscillation in the Active Galactic Nucleus 1ES 1927+654
Megan Masterson, Erin Kara, William N. Alston +15
1ES 1927+654 is an extreme active galactic nucleus (AGN) that has defied our canonical expectations for how AGN appear across the electromagnetic spectrum and how they vary on shor…
The Broadband View of the Bare Seyfert PG 1426+015: Relativistic Reflection, the Soft Excess and the Importance of Oxygen
D. J. Walton, A. Madathil-Pottayil, P. Kosec +8
We present results from a deep, coordinated - + observation of the type 1 Seyfert PG 1426+015, a source of particular interest as the most massive reverberati…
Millihertz Oscillations Near the Innermost Orbit of a Supermassive Black Hole
Megan Masterson, Erin Kara, Christos Panagiotou +22
Recent discoveries from time-domain surveys are defying our expectations for how matter accretes onto supermassive black holes (SMBHs). The increased rate of short-timescale, repet…
Effects of ultra-fast outflows on X-ray time lags in AGN
Yerong Xu, Ciro Pinto, Erin Kara +3
The time lag between soft and hard X-ray photons has been observed in many active galactic nuclei (AGN) and can reveal the accretion process and geometry around supermassive black…
Exploring the high-density reflection model for the soft excess in RBS 1124
A. Madathil-Pottayil, D. J. Walton, Javier García +13
'Bare' active galactic nuclei (AGN) are a subclass of Type 1 AGN that show little or no intrinsic absorption. They offer an unobscured view of the central regions of the AGN and th…
A New Broadband Spectral State in the Ultraluminous X-ray Source Holmberg IX X-1
D. J. Walton, M. Bachetti, P. Kosec +12
We present a series of five new broadband X-ray observations of the ultraluminous X-ray source Holmberg IX X-1, performed by - and in coordination. The first…
A systematic study of the ultra-fast outflow responses to luminosity variations in active galactic nuclei
Yerong Xu, Ciro Pinto, Daniele Rogantini +7
The extreme velocities and high ionization states of ultra-fast outflows (UFOs) make them a promising candidate for AGN feedback on the evolution of the host galaxy. However, their…
UV/Optical disk reverberation lags despite a faint X-ray corona in the AGN Mrk 335
Erin Kara, Aaron J. Barth, Edward M. Cackett +37
We present the first results from a 100-day Swift, NICER and ground-based X-ray/UV/optical reverberation mapping campaign of the Narrow-Line Seyfert 1 Mrk 335, when it was in an un…
X-ray Reverberation Mapping of Ark 564 using Gaussian Process Regression
Collin D. Lewin, Erin Kara, Daniel R. Wilkins +15
Ark 564 is an extreme high-Eddington Narrow-line Seyfert 1 galaxy, known for being one of the brightest, most rapidly variable soft X-ray AGN, and for having one of the lowest temp…
The Super-Massive Black Hole close environment in Active Galactic Nuclei
W. Alston, M. Giustini, P. O. Petrucci
Active Galactic Nuclei are powered by accretion of matter onto a supermassive black hole (SMBH) of mass Mbh ~ 10^{5}-10^{9} Msun. The accretion process is indeed the most efficient…
XMM-Newton Observations of the Narrow-Line Seyfert 1 Galaxy IRAS 132243809 : X-ray Spectral Analysis II
Jiachen Jiang, Thomas Dauser, Andrew C. Fabian +4
Previously, we modelled the X-ray spectra of the narrow-line Seyfert 1 galaxy IRAS 132243809 using a disc reflection model with a fixed electron density of cm.…
Ejection-accretion connection in NLS1 AGN 1H 1934-063
Yerong Xu, Ciro Pinto, Erin Kara +7
Accretion and ejection of matter in active galactic nuclei (AGN) are tightly connected phenomena and represent fundamental mechanisms regulating the growth of the central supermass…
High-density disc reflection spectroscopy of low-mass active galactic nuclei
L. Mallick, A. C. Fabian, J. A. García +13
The standard alpha-disc model predicts an anti-correlation between the density of the inner accretion disc and the black hole mass times square of the accretion rate, as seen in hi…
Evidence for a Compact Object in the Aftermath of the Extra-Galactic Transient AT2018cow
Dheeraj R. Pasham, Wynn C. G. Ho, William Alston +16
The brightest Fast Blue Optical Transients (FBOTs) are mysterious extragalactic explosions that may represent a new class of astrophysical phenomena. Their fast time to maximum bri…
The nature of the extreme X-ray variability in the NLS1 1H 0707-495
M. L. Parker, W. N. Alston, L. Härer +11
We examine archival XMM-Newton data on the extremely variable narrow-line Seyfert 1 (NLS1) active galactic nucleus (AGN) 1H 0707-495. We construct fractional excess variance (Fvar)…
The chameleon on the branches: spectral state transition and dips in NGC 247 ULX-1
A. D'Aì, C. Pinto, M. Del Santo +14
Soft Ultra-Luminous X-ray (ULXs) sources are a subclass of the ULXs that can switch from a supersoft spectral state, where most of the luminosity is emitted below 1 keV, to a soft…
Extreme Relativistic Reflection in the Active Galaxy ESO 033-G002
D. J. Walton, M. Balokovic, A. C. Fabian +13
We present the first high signal-to-noise broadband X-ray spectrum of the radio-quiet type-2 Seyfert ESO 033-G002, combining data from - and . The nuclear X-ra…
Broadband X-ray spectral variability of the pulsing ULX NGC 1313 X-2
A. Robba, C. Pinto, D. J. Walton +12
It is thought that ultraluminous X-ray sources (ULXs) are mainly powered by super-Eddington accreting neutron stars or black holes as shown by recent discovery of X-ray pulsations…
Quasi-periodic dipping in the ultraluminous X-ray source, NGC 247 ULX-1
W. N. Alston, C. Pinto, D. Barret +15
Most ultraluminous X-ray sources (ULXs) are believed to be stellar mass black holes or neutron stars accreting beyond the Eddington limit. Determining the nature of the compact obj…
XMM-Newton campaign on the ultraluminous X-ray source NGC 247 ULX-1: outflows
C. Pinto, R. Soria, D. Walton +13
Most ULXs are believed to be powered by super-Eddington accreting neutron stars and, perhaps, black holes. Above the Eddington rate the disc is expected to thicken and to launch po…
Modelling the Multiwavelength Variability of Mrk 335 using Gaussian Processes
Ryan-Rhys Griffiths, Jiachen Jiang, Douglas J. K. Buisson +12
The optical and UV variability of the majority of AGN may be related to the reprocessing of rapidly-changing X-ray emission from a more compact region near the central black hole.…
Discovery of soft and hard X-ray time lags in low-mass AGNs
Labani Mallick, Daniel R. Wilkins, William N. Alston +5
The scaling relations between the black hole (BH) mass and soft lag properties for both active galactic nuclei (AGNs) and BH X-ray binaries (BHXRBs) suggest the same underlying phy…
Modelling X-ray RMS spectra II: the ultra-fast outflow of PDS 456
L. Härer, M. L. Parker, A. Joyce +6
We present an improved model for excess variance spectra describing ultra-fast outflows and successfully apply it to the luminous (L ~ 10^47 erg/s) low-redshift (z = 0.184) quasar…
A Full Characterisation of the Supermassive Black Hole in IRAS 09149-6206
D. J. Walton, W. N. Alston, P. Kosec +11
We present new broadband X-ray observations of the type-I Seyfert galaxy IRAS 09149-6206, taken in 2018 with -, and . The source is highly complex, sho…