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Full-Text Articles in Astrophysics and Astronomy
Hard X-Ray Lags In Active Galactic Nuclei: Testing The Distant Reverberation Hypothesis With Ngc 6814, D. J. Walton, A. Zoghbi, E. M. Cackett, P. Uttley, F. A. Harrison, A. C. Fabian, E. Kara, J. M. Miller, R. C. Reis, C. S. Reynolds
Hard X-Ray Lags In Active Galactic Nuclei: Testing The Distant Reverberation Hypothesis With Ngc 6814, D. J. Walton, A. Zoghbi, E. M. Cackett, P. Uttley, F. A. Harrison, A. C. Fabian, E. Kara, J. M. Miller, R. C. Reis, C. S. Reynolds
Physics and Astronomy Faculty Research Publications
We present an X-ray spectral and temporal analysis of the variable active galaxy NGC 6814, observed with Suzaku during 2011 November. Remarkably, the X-ray spectrum shows no evidence for the soft excess commonly observed amongst other active galaxies, despite its relatively low level of obscuration, and is dominated across the whole Suzaku bandpass by the intrinsic powerlaw-like continuum. Despite this, we clearly detect the presence of a low-frequency hard lag of ~1600 s between the 0.5-2.0 and 2.0-5.0 keV energy bands at greater than 6σ significance, similar to those reported in the literature for a variety of other active galactic …
A Change In The Quiescent X-Ray Spectrum Of The Neutron Star Low-Mass X-Ray Binary Mxb 1659-29, E. M. Cackett, E. F. Brown, A. Cumming, N. Degenaar, J. K. Fridriksson, J. Homan, J. M. Miller, R. Wijnands
A Change In The Quiescent X-Ray Spectrum Of The Neutron Star Low-Mass X-Ray Binary Mxb 1659-29, E. M. Cackett, E. F. Brown, A. Cumming, N. Degenaar, J. K. Fridriksson, J. Homan, J. M. Miller, R. Wijnands
Physics and Astronomy Faculty Research Publications
The quasi-persistent neutron star low-mass X-ray binary MXB 1659-29 went into quiescence in 2001, and we have followed its quiescent X-ray evolution since. Observations over the first 4 yr showed a rapid drop in flux and temperature of the neutron star atmosphere, interpreted as cooling of the neutron star crust which had been heated during the 2.5 yr outburst. However, observations taken approximately 1400 and 2400 days into quiescence were consistent with each other, suggesting the crust had reached thermal equilibrium with the core. Here we present a new Chandra observation of MXB 1659-29 taken 11 yr into quiescence and …
Continued Neutron Star Crust Cooling Of The 11 Hz X-Ray Pulsar In Terzan 5: A Challenge To Heating And Cooling Models?, N. Degenaar, R. Wijnands, E. F. Brown, D. Altamirano, E. M. Cackett, J. Fridriksson, J. Homan, C. O. Heinke, J. M. Miller, D. Pooley, G. R. Sivakoff
Continued Neutron Star Crust Cooling Of The 11 Hz X-Ray Pulsar In Terzan 5: A Challenge To Heating And Cooling Models?, N. Degenaar, R. Wijnands, E. F. Brown, D. Altamirano, E. M. Cackett, J. Fridriksson, J. Homan, C. O. Heinke, J. M. Miller, D. Pooley, G. R. Sivakoff
Physics and Astronomy Faculty Research Publications
The transient neutron star low-mass X-ray binary and 11 Hz X-ray pulsar IGR J17480-2446 in the globular cluster Terzan 5 exhibited an 11 week accretion outburst in 2010. Chandra observations performed within five months after the end of the outburst revealed evidence that the crust of the neutron star became substantially heated during the accretion episode and was subsequently cooling in quiescence. This provides the rare opportunity to probe the structure and composition of the crust. Here, we report on new Chandra observations of Terzan 5 that extend the monitoring to sime2.2 yr into quiescence. We find that the thermal …
An X-Ray-Uv Correlation In Cen X-4 During Quiescence, E. M. Cackett, E. F. Brown, N. Degenaar, J. M. Miller, M. Reynolds, R. Wijnands
An X-Ray-Uv Correlation In Cen X-4 During Quiescence, E. M. Cackett, E. F. Brown, N. Degenaar, J. M. Miller, M. Reynolds, R. Wijnands
Physics and Astronomy Faculty Research Publications
Quiescent emission from the neutron star low-mass X-ray binary Cen X-4 is seen to be variable on time-scales from hundreds of seconds to years, suggesting that at least in this object, low-level accretion is important during quiescence. Here, we present results from recent XMM-Newton and Swift observations of Cen X-4, where the X-ray flux (0.5-10 keV) varies by a factor of 6.5 between the brightest and faintest states. We find a positive correlation between the X-ray flux and the simultaneous near-ultraviolet (UV) flux, where as there is no significant correlation between the X-ray and simultaneous optical (V, B) fluxes. This …
Discovery Of Fe Kα X-Ray Reverberation Around The Black Holes In Mcg-5-23-16 And Ngc 7314, A. Zoghbi, C. Reynolds, E. M. Cackett, G. Miniutti, E. Kara, A. C. Fabian
Discovery Of Fe Kα X-Ray Reverberation Around The Black Holes In Mcg-5-23-16 And Ngc 7314, A. Zoghbi, C. Reynolds, E. M. Cackett, G. Miniutti, E. Kara, A. C. Fabian
Physics and Astronomy Faculty Research Publications
Several X-ray observations have recently revealed the presence of reverberation time delays between spectral components in active galactic nuclei. Most of the observed lags are between the power-law Comptonization component, seen directly, and the soft excess produced by reflection in the vicinity of the black hole. NGC 4151 was the first object to show these lags in the iron K band. Here, we report the discovery of reverberation lags in the Fe K band in two other sources: MCG-5-23-16 and NGC 7314. In both objects, the 6-7 keV band, where the Fe Kα line peaks, lags the bands at lower …
Confirmation Of The Nature Of The Absorber In Iras 09104+4109, Chia-Ying Chiang, E. M. Cackett, P. Gandhi, A. C. Fabian
Confirmation Of The Nature Of The Absorber In Iras 09104+4109, Chia-Ying Chiang, E. M. Cackett, P. Gandhi, A. C. Fabian
Physics and Astronomy Faculty Research Publications
We present the first long Suzaku observation of the hyperluminous infrared galaxy IRAS 09104+4109 which is dominated by a Type 2 AGN. The infrared to X-ray spectral energy distribution (SED) indicates that the source is an obscured quasar with a Compton-thin absorber. However, the 3σ hard X-ray detection of the source with the BeppoSAX PDS suggested a reflection-dominated, Compton-thick view. The high-energy detection was later found to be possibly contaminated by another Type 2 AGN, NGC 2785, which is only 17 arcmin away. Our new Suzaku observation offers simultaneous soft and hard X-ray coverage and excludes contamination from NGC 2785. …