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Full-Text Articles in Physical Sciences and Mathematics
Broad Iron Lines In Neutrons Stars: Dynamical Broadening Or Wind Scattering?, E. M. Cackett, Jon M. Miller
Broad Iron Lines In Neutrons Stars: Dynamical Broadening Or Wind Scattering?, E. M. Cackett, Jon M. Miller
Physics and Astronomy Faculty Research Publications
Broad iron emission lines are observed in many accreting systems from black holes in active galactic nuclei and X-ray binaries to neutron star low-mass X-ray binaries. The origin of the line broadening is often interpreted as due to dynamical broadening and relativistic effects. However, alternative interpretations have been proposed, included broadening due to Compton scattering in a wind or accretion disk atmosphere. Here we explore the observational signatures expected from broadening in a wind, in particular that the iron line width should increase with an increase in the column density of the absorber (due to an increase in the number …
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 …
Discovery Of High-Frequency Iron K Lags In Ark 564 And Mrk 335, E. Kara, A. C. Fabian, E. M. Cackett, P. Uttley, D. R. Wilkins, A. Zoghbi
Discovery Of High-Frequency Iron K Lags In Ark 564 And Mrk 335, E. Kara, A. C. Fabian, E. M. Cackett, P. Uttley, D. R. Wilkins, A. Zoghbi
Physics and Astronomy Faculty Research Publications
We use archival XMM-Newton observations of Ark 564 and Mrk 335 to calculate the frequency-dependent time lags for these two well-studied sources. We discover high-frequency Fe K lags in both sources, indicating that the red wing of the line precedes the rest-frame energy by roughly 100 and 150 s for Ark 564 and Mrk 335, respectively. Including these two new sources, Fe K reverberation lags have been observed in seven Seyfert galaxies. We examine the low-frequency lag-energy spectrum, which is smooth, and shows no feature of reverberation, as would be expected if the low-frequency lags were produced by distant reflection …
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 A Relation Between Black Hole Mass And Soft X-Ray Time Lags In Active Galactic Nuclei, B. De Marco, G. Ponti, M. Cappi, M. Dadina, P. Uttley, E. M. Cackett, A. C. Fabian, G. Miniutti
Discovery Of A Relation Between Black Hole Mass And Soft X-Ray Time Lags In Active Galactic Nuclei, B. De Marco, G. Ponti, M. Cappi, M. Dadina, P. Uttley, E. M. Cackett, A. C. Fabian, G. Miniutti
Physics and Astronomy Faculty Research Publications
We carried out a systematic analysis of time lags between X-ray energy bands in a large sample (32 sources) of unabsorbed, radio quiet active galactic nuclei (AGN), observed by XMM-Newton. The analysis of X-ray lags (up to the highest/shortest frequencies/time-scales), is performed in the Fourier-frequency domain, between energy bands where the soft excess (soft band) and the primary power law (hard band) dominate the emission. We report a total of 15 out of 32 sources displaying a high-frequency soft lag in their light curves. All 15 are at a significance level exceeding 97 per cent and 11 are at a …
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 …
Revealing The X-Ray Source In Iras 13224-3809 Through Flux-Dependent Reverberation Lags, E. Kara, A. C. Fabian, E. M. Cackett, G. Miniutti, P. Uttley
Revealing The X-Ray Source In Iras 13224-3809 Through Flux-Dependent Reverberation Lags, E. Kara, A. C. Fabian, E. M. Cackett, G. Miniutti, P. Uttley
Physics and Astronomy Faculty Research Publications
IRAS 13224-3809 was observed in 2011 for 500 ks with the XMM-Newton observatory. We detect highly significant X-ray lags between soft (0.3-1 keV) and hard (1.2-5 keV) energies. The hard band lags the soft at low frequencies (i.e. hard lag), while the opposite (i.e. soft lag) is observed at high frequencies. In this paper, we study the lag during flaring and quiescent periods. We find that the frequency and absolute amplitude of the soft lag are different during high-flux and low-flux periods. During the low-flux intervals, the soft lag is detected at higher frequencies and with smaller amplitude. Assuming that …
A Soft X-Ray Reverberation Lag In The Agn Eso 113-G010, E. M. Cackett, A. C. Fabian, A. Zogbhi, E. Kara, C. Reynolds, P. Uttley
A Soft X-Ray Reverberation Lag In The Agn Eso 113-G010, E. M. Cackett, A. C. Fabian, A. Zogbhi, E. Kara, C. Reynolds, P. Uttley
Physics and Astronomy Faculty Research Publications
Reverberation lags have recently been discovered in a handful of nearby, variable active galactic nuclei (AGNs). Here, we analyze a ~100 ks archival XMM-Newton observation of the highly variable AGN, ESO 113-G010, in order to search for lags between hard, 1.5-4.5 keV, and soft, 0.3-0.9 keV, energy X-ray bands. At the lowest frequencies available in the light curve (lsim 1.5 × 10-4 Hz), we find hard lags where the power-law-dominated hard band lags the soft band (where the reflection fraction is high). However, at higher frequencies in the range (2-3) × 10-4 Hz we find a soft lag …
Evidence Of Light-Bending Effects And Its Implication For Spectral State Transitions, R. C. Reis, J. M. Miller, M. T. Reynolds, A. C. Fabian, D. J. Walton, E. Cackett, J. F. Steiner
Evidence Of Light-Bending Effects And Its Implication For Spectral State Transitions, R. C. Reis, J. M. Miller, M. T. Reynolds, A. C. Fabian, D. J. Walton, E. Cackett, J. F. Steiner
Physics and Astronomy Faculty Research Publications
It has long been speculated that the nature of the hard X-ray corona may be an important second driver of black hole state transitions, in addition to the mass accretion rate through the disk. However, a clear physical picture of coronal changes has not yet emerged. We present results from a systematic analysis of Rossi X-Ray Timing Explorer observations of the stellar-mass black hole binary XTE J1650-500. All spectra with significant hard X-ray detections were fit using a self-consistent, relativistically blurred disk reflection model suited to high ionization regimes. Importantly, we find evidence that both the spectral and timing properties …
The Disk-Wind-Jet Connection In The Black Hole H 1743-322, J. M. Miller, J. Raymond, A. C. Fabian, C. S. Reynolds, A. L. King, T. R. Kallman, E. M. Cackett, M. Van Der Klis, D. T. H. Steeghs
The Disk-Wind-Jet Connection In The Black Hole H 1743-322, J. M. Miller, J. Raymond, A. C. Fabian, C. S. Reynolds, A. L. King, T. R. Kallman, E. M. Cackett, M. Van Der Klis, D. T. H. Steeghs
Physics and Astronomy Faculty Research Publications
X-ray disk winds are detected in spectrally soft, disk-dominated phases of stellar-mass black hole outbursts. In contrast, compact, steady, relativistic jets are detected in spectrally hard states that are dominated by non-thermal X-ray emission. Although these distinctive outflows appear to be almost mutually exclusive, it is possible that a disk wind persists in hard states but cannot be detected via X-ray absorption lines owing to very high ionization. Here, we present an analysis of a deep, 60 ks Chandra/HETGS observation of the black hole candidate H 1743-322 in the low/hard state. The spectrum shows no evidence of a disk wind, …
A Four-Year Xmm-Newton/Chandra Monitoring Campaign Of The Galactic Centre: Analysing The X-Ray Transients, N. Degenaar, R. Wijnands, E. M. Cackett, J. Homan, J. J. M. In 'T Zand, E. Kuulkers, T. J. Maccarone, M. Van Der Klis
A Four-Year Xmm-Newton/Chandra Monitoring Campaign Of The Galactic Centre: Analysing The X-Ray Transients, N. Degenaar, R. Wijnands, E. M. Cackett, J. Homan, J. J. M. In 'T Zand, E. Kuulkers, T. J. Maccarone, M. Van Der Klis
Physics and Astronomy Faculty Research Publications
We report on the results of a four-year long X-ray monitoring campaign of the central 1.2 square degrees of our Galaxy, performed with Chandra and XMM-Newton between 2005 and 2008. Our study focuses on the properties of transient X-ray sources that reach 2-10 keV luminosities of LX ≳ 1034 erg s-1 for an assumed distance of 8 kpc. There are 17 known X-ray transients within the field of view of our campaign, eight of which were detected in outburst during our observations: the transient neutron star low-mass X-ray binaries GRS 1741-2853, AX J1745.6-2901, SAX J1747.0-2853, KS 1741-293 …
On The Role Of The Accretion Disk In Black Hole Disk-Jet Connections, J. M. Miller, G. G. Pooley, A. C. Fabian, M. A. Nowak, R. C. Reis, E. M. Cackett, K. Pottschmidt, J. Wilms
On The Role Of The Accretion Disk In Black Hole Disk-Jet Connections, J. M. Miller, G. G. Pooley, A. C. Fabian, M. A. Nowak, R. C. Reis, E. M. Cackett, K. Pottschmidt, J. Wilms
Physics and Astronomy Faculty Research Publications
Models of jet production in black hole systems suggest that the properties of the accretion disk—such as its mass accretion rate, inner radius, and emergent magnetic field—should drive and modulate the production of relativistic jets. Stellar-mass black holes in the "low/hard" state are an excellent laboratory in which to study disk-jet connections, but few coordinated observations are made using spectrometers that can incisively probe the inner disk. We report on a series of 20 Suzaku observations of Cygnus X-1 made in the jet-producing low/hard state. Contemporaneous radio monitoring was done using the Arcminute MicroKelvin Array radio telescope. Two important and …
A Comparison Of Broad Iron Emission Lines In Archival Data Of Neutron Star Low-Mass X-Ray Binaries, Edward M. Cackett, Jon M. Miller, Rubens C. Reis, Andrew C. Fabian, Didier Barret
A Comparison Of Broad Iron Emission Lines In Archival Data Of Neutron Star Low-Mass X-Ray Binaries, Edward M. Cackett, Jon M. Miller, Rubens C. Reis, Andrew C. Fabian, Didier Barret
Physics and Astronomy Faculty Research Publications
Relativistic X-ray disklines have been found in multiple neutron star low-mass X-ray binaries, in close analogy with black holes across the mass scale. These lines have tremendous diagnostic power and have been used to constrain stellar radii and magnetic fields, often finding values that are consistent with independent timing techniques. Here, we compare CCD-based data from Suzaku with Fe K line profiles from archival data taken with gas-based spectrometers. In general, we find good consistency between the gas-based line profiles from EXOSAT, BeppoSAX, and RXTE and the CCD data from Suzaku, demonstrating that the broad profiles seen are intrinsic to …
On The Determination Of The Spin Of The Black Hole In Cyg X-1 From X-Ray Reflection Spectra, A. C. Fabian, D. R. Wilkins, J. M. Miller, R. C. Reis, C. S. Reynolds, E. M. Cackett, M. A. Nowak, G. G. Pooley, K. Pottschmidt, J. S. Sanders, R. R. Ross, J. Wilms
On The Determination Of The Spin Of The Black Hole In Cyg X-1 From X-Ray Reflection Spectra, A. C. Fabian, D. R. Wilkins, J. M. Miller, R. C. Reis, C. S. Reynolds, E. M. Cackett, M. A. Nowak, G. G. Pooley, K. Pottschmidt, J. S. Sanders, R. R. Ross, J. Wilms
Physics and Astronomy Faculty Research Publications
The spin of Cygnus X-1 is measured by fitting reflection models to Suzaku data covering the energy band 0.9-400 keV. The inner radius of the accretion disc is found to lie within 2 gravitational radii (rg=GM/c2), and a value of ? is obtained for the dimensionless black hole spin. This agrees with recent measurements using the continuum fitting method by Gou et al. and of the broad iron line by Duro et al. The disc inclination is measured at ?, which is consistent with the recent optical measurement of the binary system inclination by Orosz et …
The Similarity Of Broad Iron Lines In X-Ray Binaries And Active Galactic Nuclei, D. J. Walton, R. C. Reis, E. M. Cackett, A. C. Fabian, J. M. Miller
The Similarity Of Broad Iron Lines In X-Ray Binaries And Active Galactic Nuclei, D. J. Walton, R. C. Reis, E. M. Cackett, A. C. Fabian, J. M. Miller
Physics and Astronomy Faculty Research Publications
We have compared the 2001 XMM-Newton spectra of the stellar mass black hole binary XTE J1650-500 and the active galaxy MCG-6-30-15, focusing on the broad, excess emission features at ˜4-7 keV displayed by both sources. Such features are frequently observed in both low-mass X-ray binaries and active galactic nuclei (AGN). For the former case it is generally accepted that the excess arises due to iron emission, but there is some controversy over whether their width is partially enhanced by instrumental processes, and hence also over the intrinsic broadening mechanism. Meanwhile, in the latter case, the origin of this feature is …
Relativistic Iron K X-Ray Reverberation In Ngc 4151, A. Zoghbi, A. C. Fabian, C. S. Reynolds, E. M. Cackett
Relativistic Iron K X-Ray Reverberation In Ngc 4151, A. Zoghbi, A. C. Fabian, C. S. Reynolds, E. M. Cackett
Physics and Astronomy Faculty Research Publications
Recent X-ray observations have enabled the study of reverberation delays in active galactic nuclei (AGN) for the first time. All the detections so far are in sources with a strong soft excess, and the measured delay is between the hard (1-3 keV) direct continuum and the soft excess (0.5-1 keV), interpreted as the reflection continuum smeared by relativistic effects. There is however an inherent ambiguity in identifying and studying the details of the lines in the soft excess. Here we report the first detection of reverberation in the iron K band in any AGN. Using XMM-Newton observations of NGC 4151, …
Swift Follow-Up Observations Of Unclassified Asca Sources, N. Degenaar, R. L. C. Starling, P. A. Evans, A. P. Beardmore, D. N. Burrows, E. M. Cackett, S. Campana, D. Grupe, A. Moretti, C. Pagani, K. L. Page, V. La Parola, R. Wijnands
Swift Follow-Up Observations Of Unclassified Asca Sources, N. Degenaar, R. L. C. Starling, P. A. Evans, A. P. Beardmore, D. N. Burrows, E. M. Cackett, S. Campana, D. Grupe, A. Moretti, C. Pagani, K. L. Page, V. La Parola, R. Wijnands
Physics and Astronomy Faculty Research Publications
We present Swift follow-up observations of a sample of 35 unclassified faint X-ray sources drawn from the ASCA Galactic centre and Galactic plane surveys. Our short, pointed XRT observations allow detections down to a limiting 0.3-10 keV flux of FX ~ 10-13 erg cm-2 s-1, which translates into a luminosity of LX ~ 1033 erg s-1 for an assumed distance of D = 8 kpc. The brightest source in our sample reaches a maximum 0.3-10 keV luminosity of LX ~ 2 × 1036 (D/8 kpc)2 erg s-1 during …
A Chandra Survey Of Supermassive Black Holes With Dynamical Mass Measurements, Kayhan Gültekin, Edward M. Cackett, Jon M. Miller, Tiziana Di Matteo, Sera Markoff, Douglas O. Richstone
A Chandra Survey Of Supermassive Black Holes With Dynamical Mass Measurements, Kayhan Gültekin, Edward M. Cackett, Jon M. Miller, Tiziana Di Matteo, Sera Markoff, Douglas O. Richstone
Physics and Astronomy Faculty Research Publications
We present Chandra observations of 12 galaxies that contain supermassive black holes (SMBHs) with dynamical mass measurements. Each galaxy was observed for 30 ks and resulted in a total of 68 point-source detections in the target galaxies including SMBH sources, ultraluminous X-ray sources (ULXs), and extragalactic X-ray binaries. Based on our fits of the X-ray spectra, we report fluxes, luminosities, Eddington ratios, and slope of the power-law spectrum. Normalized to the Eddington luminosity, the 2-10 keV band X-ray luminosities of the SMBH sources range from 10-8 to 10-6, and the power-law slopes are centered at ~2 with …
An Extreme X-Ray Disk Wind In The Black Hole Candidate Igr J17091-3624, A. L. King, J. M. Miller, J. Raymond, A. C. Fabian, C. S. Reynolds, T. R. Kallman, D. Maitra, E. M. Cackett, M. P. Rupen
An Extreme X-Ray Disk Wind In The Black Hole Candidate Igr J17091-3624, A. L. King, J. M. Miller, J. Raymond, A. C. Fabian, C. S. Reynolds, T. R. Kallman, D. Maitra, E. M. Cackett, M. P. Rupen
Physics and Astronomy Faculty Research Publications
Chandra spectroscopy of transient stellar-mass black holes in outburst has clearly revealed accretion disk winds in soft, disk-dominated states, in apparent anti-correlation with relativistic jets in low/hard states. These disk winds are observed to be highly ionized, dense, and to have typical velocities of ~1000 km s-1 or less projected along our line of sight. Here, we present an analysis of two Chandra High Energy Transmission Grating spectra of the Galactic black hole candidate IGR J17091-3624 and contemporaneous Expanded Very Large Array (EVLA) radio observations, obtained in 2011. The second Chandra observation reveals an absorption line at 6.91 ± …
Identifying A New Intermediate Polar Using Xmm-Newton And Integral, Matthew J. Middleton, Edward M. Cackett, Craig Shaw, Gavin Ramsay, Timothy P. Roberts, Peter J. Wheatley
Identifying A New Intermediate Polar Using Xmm-Newton And Integral, Matthew J. Middleton, Edward M. Cackett, Craig Shaw, Gavin Ramsay, Timothy P. Roberts, Peter J. Wheatley
Physics and Astronomy Faculty Research Publications
The bright X-ray source 2XMMi J180438.7-145647 is fortunate to have long baseline observations in INTEGRAL that complement observations taken by other missions. Optical spectroscopy of this object has suggested a distance of ˜7 kpc and an identification with a low-mass X-ray binary. We instead use the X-ray data from 0.3 to 40 keV to identify the source as a bright intermediate polar (IP) with an estimate for the white dwarf mass of ˜0.60 M⊙. This identification is supported by the presence of an iron triplet, the component lines of which are some of the strongest seen in IPs, …
The Variable Quiescent X-Ray Emission Of The Neutron Star Transient Xte J1701-462, Joel K. Fridriksson, Jeroen Homan, Rudy Wijnands, Edward M. Cackett, Diego Altamirano, Nathalie Degenaar, Edward F. Brown, Mariano Méndez, Tomaso M. Belloni
The Variable Quiescent X-Ray Emission Of The Neutron Star Transient Xte J1701-462, Joel K. Fridriksson, Jeroen Homan, Rudy Wijnands, Edward M. Cackett, Diego Altamirano, Nathalie Degenaar, Edward F. Brown, Mariano Méndez, Tomaso M. Belloni
Physics and Astronomy Faculty Research Publications
We present the results of continued monitoring of the quiescent neutron star low-mass X-ray binary XTE J1701-462 with Chandra and Swift. A new Chandra observation from 2010 October extends our tracking of the neutron star surface temperature from ≃ 800 days to ≃ 1160 days since the end of an exceptionally luminous 19 month outburst. This observation indicates that the neutron star crust may still be slowly cooling toward thermal equilibrium with the core; another observation further into quiescence is needed to verify this. The shape of the overall cooling curve is consistent with that of a broken power law, …
Quiescent X-Ray Variability From The Neutron Star Transient Aql X-1, E. M. Cackett, J. K. Fridriksson, J. Homan, J. M. Miller, R. Wijnands
Quiescent X-Ray Variability From The Neutron Star Transient Aql X-1, E. M. Cackett, J. K. Fridriksson, J. Homan, J. M. Miller, R. Wijnands
Physics and Astronomy Faculty Research Publications
A number of studies have revealed variability from neutron star low-mass X-ray binaries during quiescence. Such variability is not well characterized, or understood, but may be a common property that has been missed due to lack of multiple observations. One such source where variability has been observed is Aql X-1. Here, we analyse 14 Chandra and XMM-Newton observations of Aql X-1 in quiescence, covering a period of approximately 2 yr. There is clear variability between the epochs, with the most striking feature being a flare-like increase in the flux by a factor of 5. Spectral fitting is inconclusive as to …
Further X-Ray Observations Of Exo 0748-676 In Quiescence: Evidence For A Cooling Neutron Star Crust, N. Degenaar, M. T. Wolff, P. S. Ray, K. S. Wood, J. Homan, W. H. G. Lewin, P. G. Jonker, E. M. Cackett, J. M. Miller, E. F. Brown, R. Wijnands
Further X-Ray Observations Of Exo 0748-676 In Quiescence: Evidence For A Cooling Neutron Star Crust, N. Degenaar, M. T. Wolff, P. S. Ray, K. S. Wood, J. Homan, W. H. G. Lewin, P. G. Jonker, E. M. Cackett, J. M. Miller, E. F. Brown, R. Wijnands
Physics and Astronomy Faculty Research Publications
In late 2008, the quasi-persistent neutron star X-ray transient and eclipsing binary EXO 0748-676 started a transition from outburst to quiescence, after it actively accreted for more than 24 yr. In a previous work, we discussed Chandra and Swift observations obtained during the first 5 months of this transition. Here, we report on further X-ray observations of EXO 0748-676, extending the quiescent monitoring to 1.6 yr. Chandra and XMM-Newton data reveal quiescent X-ray spectra composed of a soft, thermal component that is well fitted by a neutron star atmosphere model. An additional hard power-law tail is detected that changes non-monotonically …
Multistate Observations Of The Galactic Black Hole Xte J1752-223: Evidence For An Intermediate Black Hole Spin, R. C. Reis, J. M. Miller, A. C. Fabian, E. M. Cackett, D. Maitra, C. S. Reynolds, M. Rupen, D. T. H. Steeghs, R. Wijnands
Multistate Observations Of The Galactic Black Hole Xte J1752-223: Evidence For An Intermediate Black Hole Spin, R. C. Reis, J. M. Miller, A. C. Fabian, E. M. Cackett, D. Maitra, C. S. Reynolds, M. Rupen, D. T. H. Steeghs, R. Wijnands
Physics and Astronomy Faculty Research Publications
The Galactic black hole candidate XTE J1752-223 was observed during the decay of its 2009 outburst with the Suzaku and XMM-Newton observatories. The observed spectra are consistent with the source being in the ‘intermediate’ and ‘low-hard’ states, respectively. The presence of a strong, relativistic iron emission line is clearly detected in both observations and the line profiles are found to be remarkably consistent and robust to a variety of continuum models. This strongly points to the compact object in XTE J1752-223 being a stellar mass black hole accretor and not a neutron star. Physically motivated and self-consistent reflection models for …
On Relativistic Disk Spectroscopy In Compact Objects With X-Ray Ccd Cameras, J. M. Miller, A. D'Aì, M. W. Bautz, S. Bhattacharyya, D. N. Burrows, E. M. Cackett, A. C. Fabian, M. J. Freyberg, F. Haberl, J. Kennea, M. A. Nowak, R. C. Reis, T. E. Strohmayer, M. Tsujimoto
On Relativistic Disk Spectroscopy In Compact Objects With X-Ray Ccd Cameras, J. M. Miller, A. D'Aì, M. W. Bautz, S. Bhattacharyya, D. N. Burrows, E. M. Cackett, A. C. Fabian, M. J. Freyberg, F. Haberl, J. Kennea, M. A. Nowak, R. C. Reis, T. E. Strohmayer, M. Tsujimoto
Physics and Astronomy Faculty Research Publications
X-ray charge-coupled devices (CCDs) are the workhorse detectors of modern X-ray astronomy. Typically covering the 0.3-10.0 keV energy range, CCDs are able to detect photoelectric absorption edges and K shell lines from most abundant metals. New CCDs also offer resolutions of 30-50 (E/ΔE), which is sufficient to detect lines in hot plasmas and to resolve many lines shaped by dynamical processes in accretion flows. The spectral capabilities of X-ray CCDs have been particularly important in detecting relativistic emission lines from the inner disks around accreting neutron stars and black holes. One drawback of X-ray CCDs is that spectra can be …
Continued Cooling Of The Crust In The Neutron Star Low-Mass X-Ray Binary Ks 1731-260, Edward M. Cackett, Edward F. Brown, Andrew Cumming, Nathalie Degenaar, Jon M. Miller, Rudy Wijnands
Continued Cooling Of The Crust In The Neutron Star Low-Mass X-Ray Binary Ks 1731-260, Edward M. Cackett, Edward F. Brown, Andrew Cumming, Nathalie Degenaar, Jon M. Miller, Rudy Wijnands
Physics and Astronomy Faculty Research Publications
Some neutron star low-mass X-ray binaries have very long outbursts (lasting several years) which can generate a significant amount of heat in the neutron star crust. After the system has returned to quiescence, the crust then thermally relaxes. This provides a rare opportunity to study the thermal properties of neutron star crusts, putting constraints on the thermal conductivity and hence the structure and composition of the crust. KS 1731-260 is one of only four systems where this crustal cooling has been observed. Here, we present a new Chandra observation of this source approximately eight years after the end of the …
Quiescent X-Ray Emission From Cen X-4: A Variable Thermal Component, Edward M. Cackett, Edward F. Brown, Jon M. Miller, Rudy Wijnands
Quiescent X-Ray Emission From Cen X-4: A Variable Thermal Component, Edward M. Cackett, Edward F. Brown, Jon M. Miller, Rudy Wijnands
Physics and Astronomy Faculty Research Publications
The nearby neutron star low-mass X-ray binary, Cen X-4, has been in a quiescent state since its last outburst in 1979. Typically, quiescent emission from these objects consists of thermal emission (presumably from the neutron star surface) with an additional hard power-law tail of unknown nature. Variability has been observed during quiescence in Cen X-4 on both timescales as short as hundreds of seconds and as long as years. However, the nature of this variability is still unknown. Early observations seemed to show it was all due to a variable hard X-ray tail. Here, we present new and archival observations …
Relativistic Lines And Reflection From The Inner Accretion Disks Around Neutron Stars, Edward M. Cackett, Jon M. Miller, David R. Ballantyne, Didier Barret, Sudip Bhattacharyya, Martin Boutelier, M. Coleman Miller, Tod E. Strohmayer, Rudy Wijnands
Relativistic Lines And Reflection From The Inner Accretion Disks Around Neutron Stars, Edward M. Cackett, Jon M. Miller, David R. Ballantyne, Didier Barret, Sudip Bhattacharyya, Martin Boutelier, M. Coleman Miller, Tod E. Strohmayer, Rudy Wijnands
Physics and Astronomy Faculty Research Publications
A number of neutron star low-mass X-ray binaries (LMXBs) have recently been discovered to show broad, asymmetric Fe K emission lines in their X-ray spectra. These lines are generally thought to be the most prominent part of a reflection spectrum, originating in the inner part of the accretion disk where strong relativistic effects can broaden emission lines. We present a comprehensive, systematic analysis of Suzaku and XMM-Newton spectra of 10 neutron star LMXBs, all of which display broad Fe K emission lines. Of the 10 sources, 4 are Z sources, 4 are atolls, and 2 are accreting millisecond X-ray pulsars …