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2013

Wayne State University

Physics and Astronomy Faculty Research Publications

Articles 1 - 19 of 19

Full-Text Articles in Physical Sciences and Mathematics

Electron-Impact Vibrational Excitation Of Vibrationally Excited H2 Molecules Involving The Resonant 2(Sigma)G+ Rydberg-Excited Electronic State, R Celiberto, R. K. Janev, V Laporta, J Tennyson, J. M. Wadehra Dec 2013

Electron-Impact Vibrational Excitation Of Vibrationally Excited H2 Molecules Involving The Resonant 2(Sigma)G+ Rydberg-Excited Electronic State, R Celiberto, R. K. Janev, V Laporta, J Tennyson, J. M. Wadehra

Physics and Astronomy Faculty Research Publications

Electron-impact theoretical cross sections and rate coefficients for vibrational excitation of vibrationally excited H2 molecules, occurring through the H−2 resonant species in the 2Σ+g Rydberg-excited electronic state, are presented. The cross sections are calculated as functions of the incident electron energy by adopting the local-complex-potential model for resonant collisions and by using ab initio calculated molecular potentials and resonance widths. The calculations have been extended to all possible vibrational transitions linking all 15 vibrational levels of the electronic ground state of the H2 molecule. The corresponding rate coefficients are also obtained as a function of the electron temperature by assuming …

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Broad Iron Lines In Neutrons Stars: Dynamical Broadening Or Wind Scattering?, E. M. Cackett, Jon M. Miller Nov 2013

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 …

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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 Nov 2013

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 …

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Calculating Time Lags From Unevenly Sampled Light Curves, A. Zoghbi, C. Reynolds, E. M. Cackett Nov 2013

Calculating Time Lags From Unevenly Sampled Light Curves, A. Zoghbi, C. Reynolds, E. M. Cackett

Physics and Astronomy Faculty Research Publications

Timing techniques are powerful tools to study dynamical astrophysical phenomena. In the X-ray band, they offer the potential of probing accretion physics down to the event horizon. Recent work has used frequency- and energy-dependent time lags as tools for studying relativistic reverberation around the black holes in several Seyfert galaxies. This was achieved due to the evenly sampled light curves obtained using XMM-Newton. Continuously sampled data are, however, not always available and standard Fourier techniques are not applicable. Here, building on the work of Miller et al., we discuss and use a maximum likelihood method to obtain frequency-dependent lags that …

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Comment On "Unified Formalism Of Adreev Reflection At A Ferromagnet/Superconductor Interface", M. Eschrig, A. A. Golubov, I. I. Mazin, B. Nadgorny, Y. Tanaka, O. T. Valls, Igor Žutić Sep 2013

Comment On "Unified Formalism Of Adreev Reflection At A Ferromagnet/Superconductor Interface", M. Eschrig, A. A. Golubov, I. I. Mazin, B. Nadgorny, Y. Tanaka, O. T. Valls, Igor Žutić

Physics and Astronomy Faculty Research Publications

A Comment on the Letter by T. Y. Chen et al., Phys. Rev. Lett. 109 146602 (2012) The authors of the Letter offer a Reply.

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Freeze-Out Dynamics Via Charged Kaon Femtoscopy In √ Snn = 200 Gev Central Au + Au Collisions, L. Adamczyk, E. Elnimr, S. Lapointe, C. Pruneau, J. Putschke, M. Sharma, L. H. Tarini, S. A. Voloshin, Star Collaboration Sep 2013

Freeze-Out Dynamics Via Charged Kaon Femtoscopy In √ Snn = 200 Gev Central Au + Au Collisions, L. Adamczyk, E. Elnimr, S. Lapointe, C. Pruneau, J. Putschke, M. Sharma, L. H. Tarini, S. A. Voloshin, Star Collaboration

Physics and Astronomy Faculty Research Publications

We present measurements of three-dimensional correlation functions of like-sign, low-transverse-momentum kaon pairs from √sNN=200 GeV Au+Au collisions. A Cartesian surface-spherical harmonic decomposition technique was used to extract the kaon source function. The latter was found to have a three-dimensional Gaussian shape and can be adequately reproduced by Therminator event-generator simulations with resonance contributions taken into account. Compared to the pion one, the kaon source function is generally narrower and does not have the long tail along the pair transverse momentum direction. The kaon Gaussian radii display a monotonic decrease with increasing transverse mass mT over …

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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 Sep 2013

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 …

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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 Sep 2013

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 …

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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 Sep 2013

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 …

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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 Sep 2013

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 …

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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 Aug 2013

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 …

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1es 1927+654: A Bare Seyfert 2, L. C. Gallo, C. Macmackin, R. Vasudevan, E. M. Cackett, A. C. Fabian, F. Panessa Jul 2013

1es 1927+654: A Bare Seyfert 2, L. C. Gallo, C. Macmackin, R. Vasudevan, E. M. Cackett, A. C. Fabian, F. Panessa

Physics and Astronomy Faculty Research Publications

1ES 1927+654 is an active galactic nucleus (AGN) tbat appears to defy the unification model. It exhibits a type-2 optical spectrum, but possesses little X-ray obscuration. XMM-Newton and Suzaku observations obtained in 2011 are used to study the X-ray properties of 1ES 1927+654. The spectral energy distribution derived from simultaneous optical-to-X-ray data obtained with XMM-Newton shows that the AGN has a typical Eddington ratio (L/LEdd = 0.014 ··· 0.11). The X-ray spectrum and rapid variability are consistent with originating from a corona surrounding a standard accretion disc. Partial covering models can describe the X-ray data: however, the narrow …

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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 May 2013

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 …

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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 Apr 2013

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 …

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Confirmation Of The Nature Of The Absorber In Iras 09104+4109, Chia-Ying Chiang, E. M. Cackett, P. Gandhi, A. C. Fabian Apr 2013

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. …

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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 Apr 2013

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 …

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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 Feb 2013

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 …

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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 Jan 2013

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 …

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Regulation Of Black Hole Winds And Jets Across The Mass Scale, A. L. King, J. M. Miller, J. Raymond, A. C. Fabian, C. S. Reynolds, K. Gültekin, E. M. Cackett, S. W. Allen, D. Proga, T. R. Kallman Jan 2013

Regulation Of Black Hole Winds And Jets Across The Mass Scale, A. L. King, J. M. Miller, J. Raymond, A. C. Fabian, C. S. Reynolds, K. Gültekin, E. M. Cackett, S. W. Allen, D. Proga, T. R. Kallman

Physics and Astronomy Faculty Research Publications

We present a study of the mechanical power generated by both winds and jets across the black hole mass scale. We begin with the study of ionized X-ray winds and present a uniform analysis using Chandra grating spectra. The high-quality grating spectra facilitate the characterization of the outflow velocity, ionization, and column density of the absorbing gas. We find that the kinetic power of the winds, derived from these observed quantities, scales with increasing bolometric luminosity as log (L wind, 42/Cv ) = (1.58 ± 0.07)log (L Bol, 42) - (3.19 ± 0.19). This suggests that supermassive …

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