Browsing Articles by Subject "Active galactic nuclei"

Now showing items 1-17 of 17

1ES 1927+654: a bare Seyfert 2

Gallo, Luigi C.; MacMackin, C.; Vasudevan, R.; Cackett, E. M.; Fabian, A. C.; Panessa, F. (Oxford University Press, 2013-07)

1ES 1927+654 is an active galactic nucleus (AGN) that appears to defy the unification model. It exhibits a type-2 optical spectrum, but possesses little X-ray obscuration. XMM–Newton and Suzaku ...
Accretion disc particle accretion in major merger simulations

Wurster, James Howard; Thacker, Robert John, 1970- (Oxford University Press, 2013-05)

A recent approach to simulating localized feedback from active galactic nuclei (AGN) by Power et al. uses an accretion disc particle to represent both the black hole and its accretion disc. We have extrapolated and adapted ...
Caught in the act: measuring the changes in the corona that cause the extreme variability of 1H 0707−495

Wilkins, D. R.; Kara, E.; Fabian, A. C.; Gallo, Luigi C. (Oxford University Press, 2014-09-21)

The X-ray spectra of the narrow-line Seyfert 1 galaxy, 1H 0707–495, obtained with XMM–Newton, from time periods of varying X-ray luminosity are analysed in the context of understanding the changes to the X-ray ...
A comparative study of AGN feedback algorithms

Wurster, James Howard; Thacker, Robert John, 1970- (Oxford University Press, 2013-05)

Modelling active galactic nuclei (AGN) feedback in numerical simulations is both technically and theoretically challenging, with numerous approaches having been published in the literature. We present a study of five ...
The Comptonization of accretion disc X-ray emission: consequences for X-ray reflection and the geometry of AGN coronae

Wilkins, D. R.; Gallo, Luigi C. (Oxford University Press, 2015-03-21)

We consider the Comptonization of the photons that make up the relativistically blurred reflection that is commonly detected from the accretion discs of active galactic nuclei by the coronae of energetic particles believed ...
The discovery of the first “changing look” quasar: new insights into the physics and phenomenology of active galactic nuclei

LaMassa, Stephanie M.; Cales, Sabrina; Moran, Edward C.; Myers, Adam D.; Richards, Gordon T.; Eracleous, Michael; Heckman, Timothy M.; Gallo, Luigi C.; Urry, C. Megan (American Astronomical Society, 2015-02-20)

SDSS J015957.64+003310.5 is an X-ray selected, z = 0.31 active galactic nucleus (AGN) from the Stripe 82X survey that transitioned from a Type 1 quasar to a Type 1.9 AGN between 2000 and 2010. This is the most distant AGN, ...
How well can we measure supermassive black hole spin?

Bonson, K.; Gallo, Luigi C. (Oxford University Press, 2016-05-11)

Being one of only two fundamental properties black holes possess, the spin of supermassive black holes (SMBHs) is of great interest for understanding accretion processes and galaxy evolution. However, in these early days ...
Modelling the broad Fe K alpha reverberation in the AGN NGC 4151

Cackett, E. M.; Zoghbi, A.; Reynolds, C.; Fabian, A. C.; Kara, E.; Uttley, P.; Wilkins, D. R. (Oxford University Press, 2014-01-13)

The recent detection of X-ray reverberation lags, especially in the Fe Kα line region, around active galactic nuclei (AGN) has opened up the possibility of studying the time-resolved response (reflection) of hard ...
Nuclear spallation in active galaxies

Gallo, Luigi. C.; Randhawa, J. S.; Waddell, S. G. H.; Hani, M. H.; Garcia, J. A.; Reynolds, C.S. (Oxford University Press, 2019-01-25)

A number of works point to the presence of narrow emission features at unusual energies in the X-ray spectra of active galactic nuclei or to potentially low iron abundances as possible evidence for the spallation of iron. ...
The NuSTAR spectrum of Mrk 335: extreme relativistic effects within two gravitational radii of the event horizon

Parker, M. L.; Wilkins, D. R.; Fabian, A. C.; Grupe, D.; Dauser, T.; Matt, G.; Harrison, F. A.; Brenneman, L.; Boggs, S. E.; Christensen, F. E.; Gallo, Luigi C. (Oxford University Press, 2014-09-11)

We present 3–50 keV NuSTAR observations of the active galactic nuclei Mrk 335 in a very low flux state. The spectrum is dominated by very strong features at the energies of the iron line at 5–7 keV and Compton ...
The origin of blueshifted absorption features in the X-ray spectrum of PG 1211+143: outflow or disc

Gallo, Luigi C.; Fabian, A. C. (Oxford University Press, 2013-09)

In some radio-quiet active galactic nuclei (AGN), high-energy absorption features in the X-ray spectra have been interpreted as ultrafast outflows (UFOs) – highly ionized material (e.g. Fe XXV and Fe XXVI) ejected at mildly ...
A selection effect boosting the contribution from rapidly spinning black holes to the cosmic X-ray background

Vasudevan, R. V.; Fabian, A. C.; Reynolds, C. S.; Aird, J.; Dauser, T.; Gallo, Luigi C. (Oxford University Press, 2016-05-11)

The cosmic X-ray background (CXB) is the total emission from past accretion activity on to supermassive black holes in active galactic nuclei (AGN) and peaks in the hard X-ray band (30 keV). In this paper, we identify a ...
Suzaku observations of Mrk 335: confronting partial covering and relativistic reflection

Gallo, Luigi C.; Wilkins, D. R.; Bonson, K.; Chiang, C.-Y.; Grupe, D.; Parker, M. L.; Zoghbi, A.; Fabian, A. C.; Komossa, S.; Longinotti, A. L. (Oxford University Press, 2015-01)

We report on the deepest X-ray observation of the narrow-line Seyfert 1 galaxy Mrk 335 in the low-flux state obtained with Suzaku. The data are compared to a 2006 high-flux Suzaku observation when the source was ∼10 times ...
Suzaku observations of ‘bare’ active galactic nuclei

Walton, D. J.; Nardini, E.; Fabian, A. C.; Gallo, Luigi C.; Reis, R. C. (Oxford University Press, 2013-02)

We present an X-ray spectral analysis of a large sample of 25 ‘bare’ active galactic nuclei (AGN), sources with little or no complicating intrinsic absorption, observed with Suzaku. Our work focuses on studying the potential ...
Towards modelling X-ray reverberation in AGN: piecing together the extended corona

Wilkins, D. R.; Cackett, E. M.; Fabian, A. C.; Reynolds, C. S. (Oxford University Press, 2016-05-01)

Models of X-ray reverberation from extended coronae are developed from general relativistic ray tracing simulations. Reverberation lags between correlated variability in the directly observed continuum emission and that ...
X-ray spectral and variability properties of low-mass active galactic nuclei

Ludlam, R. M.; Cackett, E. M.; Gultekin, K.; Fabian, A. C.; Gallo, Luigi C.; Miniutti, G. (Oxford University Press, 2015-03)

We study the X-ray properties of a sample of 14 optically selected low-mass active galactic nuclei (AGN) whose masses lie within the range 10[superscript 5]–2 × 10[superscript 6] M[subscript circled dot] with XMM–Newton. ...
XMM-Newton observations of the narrow-line Seyfert 1 galaxy Mrk 335 in a historical low X-ray flux state

Gallo, Luigi C.; Grupe, Dirk; Komossa, Stefanie; Fabian, Andrew C.; Larsson, Josefin; Pradhan, Anil K.; Xu, Dawei; Miniutti, Giovanni (American Astronomical Society, 2008-07)

We report the discovery of strong soft X-ray emission lines and a hard continuum above 2 keV in the narrow-line Seyfert 1 galaxy Mrk 335 during an extremely low X-ray flux state. Mrk 335 was observed for 22 ks by XMM-Newton ...