Kendrah D. Murphy

Skidmore College, Saratoga Springs, New York, United States

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Publications (21)55.76 Total impact

  • Source
    T. Yaqoob, K. D. Murphy, L. Miller, T. J. Turner
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    ABSTRACT: The absolute luminosity of the Fe Kalpha emission line from matter illuminated by X-rays in astrophysical sources is nontrivial to calculate except when the line-emitting medium is optically-thin to absorption and scattering. We characterize the Fe Kalpha line flux using a dimensionless efficiency, defined as the fraction of continuum photons above the Fe K shell absorption edge threshold energy that appear in the line. The optically-thin approximation begins to break down even for column densities as small as 2 x 10^22 cm^-2. We show how to obtain reliable estimates of the Fe Kalpha line efficiency in the case of cold, neutral matter, even for the Compton-thick regime. We find that, regardless of geometry and covering factor, the largest Fe Kalpha line efficiency is attained well before the medium becomes Compton-thick. For cosmic elemental abundances it is difficult to achieve an efficiency higher than a few percent under the most favorable conditions and lines of sight. For a given geometry, Compton-thick lines-of-sight may have Fe Kalpha line efficiencies that are orders of magnitude less than the maximum possible for that geometry. Configurations that allow unobscured views of a Compton-thick reflecting surface are capable of yielding the highest efficiencies. Our results can be used to estimate the predicted flux of the narrow Fe Kalpha line at ~6.4 keV from absorption models in AGN. In particular we show that contrary to a recent claim in the literature, absorption dominated models for the relativistic Fe Kalpha emission line in MCG -6-30-15 do not over-predict the narrow Fe Kalpha line for any column density or covering factor. Comment: Accepted for publication in MNRAS. Seven pages, 2 figures
    Monthly Notices of the Royal Astronomical Society 07/2011; 415(4):3966 - 3967. · 5.52 Impact Factor
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    Kendrah D. Murphy, Tahir Yaqoob
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    ABSTRACT: The central engines of both type 1 and type 2 active galactic nuclei are thought to harbour a toroidal structure that absorbs and reprocesses high-energy photons from the central X-ray source. Unique features in the reprocessed spectra can provide powerful physical constraints on the geometry, column density, element abundances and orientation of the circumnuclear matter. If the reprocessor is Compton-thick, the calculation of emission-line and continuum spectra that are suitable for direct fitting to X-ray data is challenging because the reprocessed emission depends on the spectral shape of the incident continuum, which may not be directly observable. We present new Monte Carlo calculations of Green's functions for a toroidal reprocessor that provide significant improvements over currently available models. The Green's function approach enables the construction of X-ray spectral fitting models that allow arbitrary incident spectra as part of the fitting process. The calculations are fully relativistic and have been performed for column densities that cover the Compton-thin to Compton-thick regime, for incident photon energies up to 500 keV. The Green's function library can easily be extended cumulatively to provide models that are valid for higher input energies and a wider range of element abundances and opening angles of the torus. The reprocessed continuum and fluorescent line emission due to Fe Kα, Fe Kβ and Ni Kα are treated self-consistently, eliminating the need for ad hoc modelling that is currently common practice. We find that the spectral shape of the Compton-thick reflection spectrum in both the soft and hard X-ray bands in our toroidal geometry is different compared with that obtained from disc models. A key result of our study is that a Compton-thick toroidal structure that subtends the same solid angle at the X-ray source as a disc can produce a reflection spectrum that is ~6 times weaker than that from a disc. This highlights the widespread and erroneous interpretation of the so-called `reflection-fraction' as a solid angle, obtained from fitting disc-reflection models to Compton-thick sources without regard for proper consideration of geometry.
    Monthly Notices of the Royal Astronomical Society 01/2011; 415:3962-3965. · 5.52 Impact Factor
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    Tahir Yaqoob, Kendrah D. Murphy
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    ABSTRACT: We present new results from Monte Carlo calculations of the flux and equivalent width (EW) of the Ni Kalpha fluorescent emission line in the toroidal X-ray reprocessor model of Murphy & Yaqoob. In the Compton-thin regime, the EW of the Ni Kalpha line is a factor of ˜22 less than that of the Fe Kalpha line but this factor can be as low as ˜6 in the Compton-thick regime. We show that the optically thin limit for this ratio depends only on the Fe to Ni abundance ratio, it being independent of the geometry and covering factor of the reprocessor, and also independent of the shape of the incident X-ray continuum. We give some useful analytic expressions for the absolute flux and the EW of the Ni Kalpha line in the optically thin limit. When the reprocessor is Compton thick and the incident continuum is a power law with a photon index of 1.9, the Ni Kalpha EW has a maximum value of ˜3 and ˜250 eV for non-intercepting and intercepting lines of sight, respectively. Larger EWs are obtained for flatter continua. We have also studied the Compton shoulder of the Ni Kalpha line and find that the ratio of scattered to unscattered flux in the line has a maximum value of 0.26, less than the corresponding maximum for the Fe Kalpha line. However, we find that the shape of the Compton shoulder profile for a given column density and inclination angle of the torus is similar to the corresponding profile for the Fe Kalpha line. Our results will be useful for interpreting X-ray spectra of active galactic nuclei (AGNs) and X-ray binary systems in which the system parameters are favourable for the Ni Kalpha line to be detected.
    Monthly Notices of the Royal Astronomical Society 01/2011; 412:1765-1770. · 5.52 Impact Factor
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    Tahir Yaqoob, Kendrah D. Murphy
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    ABSTRACT: Heavily obscured active galactic nuclei (AGNs) play an important role in contributing to the cosmic X-ray background (CXRB). However, the AGNs found in deep X-ray surveys are often too weak to allow direct measurement of the column density of obscuring matter. One method adopted in recent years to identify heavily obscured, Compton-thick AGNs under such circumstances is to use the observed mid-infrared to X-ray luminosity ratio as a proxy for the column density. This is based on the supposition that the amount of energy lost by the illuminating X-ray continuum to the obscuring matter and reprocessed into infrared emission is directly related to the column density and that the proxy is not sensitive to other physical parameters of the system (aside from contamination by dust emission from, for example, star-forming regions). Using Monte Carlo simulations, we find that the energy losses experienced by the illuminating X-ray continuum in the obscuring matter are far more sensitive to the shape of the X-ray continuum and to the covering factor of the X-ray reprocessor than they are to the column density of the material. Specifically we find that it is possible for the infrared to X-ray luminosity ratio for a Compton-thin source to be just as large as that for a Compton-thick source even without any contamination from dust. Since the intrinsic X-ray continuum and covering factor of the reprocessor are poorly constrained from deep X-ray survey data, we conclude that the mid-infrared to X-ray luminosity ratio is not a reliable proxy for the column density of obscuring matter in AGNs even when there is no other contribution to the mid-infrared luminosity aside from X-ray reprocessing. This conclusion is independent of the geometry of the obscuring matter. Comment: Accepted for publication in MNRAS. 12 pages, 7 figures
    Monthly Notices of the Royal Astronomical Society 10/2010; · 5.52 Impact Factor
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    Tahir Yaqoob, Kendrah D. Murphy
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    ABSTRACT: We present new, high signal-to-noise ratio results from a Monte Carlo study of the properties of the Compton shoulder of the Fe Kalpha emission line in the toroidal X-ray reprocessor model of Murphy & Yaqoob (2009, MNRAS, 397, 1549). The model comprehensively covers the Compton-thin to Compton-thick regimes and we find that the variety of Compton shoulder profiles is greater than that for both (centrally-illuminated) spherical and disk geometries. Our Monte Carlo simulations were done with a statistical accuracy that is high enough to reveal, for the case of an edge-on, Compton-thick torus, a new type of Compton shoulder that is not present in the spherical or disk geometries. Such a Compton shoulder is dominated by a narrow back-scattering feature at ~6.24 keV. Our results also reveal a dependence of the shape of the Compton shoulder (and its magnitude relative to the Fe Kalpha line core) on the spectral shape of the incident X-ray continuum. We also show the effects of velocity broadening on the Fe Kalpha line profile and find that if either the velocity width or instrument resolution is greater than a FWHM of ~2000 km/s, the Compton shoulder begins to become blended with the line core and the characteristic features of the Compton shoulder become harder to resolve. In particular, at a FWHM of ~7000 km/s the Compton shoulder is NOT resolved at all, its only signature being a weak asymmetry in the blended line profile. Thus, CCD X-ray detectors cannot unambiguously resolve the Compton shoulder. Our results are freely available in a format that is suitable for direct spectral-fitting of the continuum and line model to real data. Comment: Accepted for publication in MNRAS. 12 pages, 6 figures. Abstract is abridged
    Monthly Notices of the Royal Astronomical Society 10/2010; · 5.52 Impact Factor
  • Kendrah D. Murphy, T. Yaqoob
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    ABSTRACT: Obscured AGN are widely recognized to play a critical role in AGN evolution and the accretion history of the universe. These objects are furthermore thought to make a significant contribution to the cosmic X-ray background (CXRB), although their contribution relative to unobscured AGN, especially with respect to a possible "hidden" population of obscured AGN, remains a topic of debate. The infrared to X-ray luminosity ratio is often used as an indicator of Compton-thick AGN, especially for weak sources in deep surveys. We present new theoretical energy-loss calculations that allow us to investigate the relationship between this luminosity ratio due to X-ray reprocessing, and the column density of the reprocessor. We will discuss the reliability of the infrared to X-ray luminosity ratio as a diagnostic of the column density. We will furthermore discuss observed-to-intrinsic X-ray luminosity ratio calculations, showing that even hard X-ray surveys are biased against detecting obscured Compton-thick AGN. However, if a source is viewed through an unobscured line-of-sight, the reprocessing material out of the line-of-sight can significantly enhance the apparent luminosity, if the Compton depth is greater than 1. X-ray surveys will therefore favor detections of unobscured AGN with Compton-thick reprocessors rather than obscured Compton-thick sources.
    02/2010;
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    ABSTRACT: We present the analysis of an XMM-Newton observation of the Seyfert galaxy NGC 2992. The source was found in its highest level of X-ray activity yet detected, a factor ~23.5 higher in the 2-10 keV flux than the historical minimum. NGC 2992 is known to exhibit X-ray flaring activity on timescales of days to weeks, and the XMM-Newton data provide at least a factor of ~3 better spectral resolution in the Fe K band than any previously measured flaring X-ray state. We find that there is a broad feature in the ~5-7 keV band that could be interpreted as a relativistic Fe Kalpha emission line. Its flux appears to have increased in tandem with the 2-10 keV continuum when compared to a previous Suzaku observation when the continuum was a factor of ~8 lower than that during the XMM-Newton observation. The XMM-Newton data are consistent with the general picture that increased X-ray activity and corresponding changes in the Fe Kalpha line emission occur in the innermost regions of the putative accretion disk. This behavior contrasts with the behavior of other active galactic nuclei in which the Fe Kalpha line does not respond to variability in the X-ray.
    The Astrophysical Journal 01/2010; 713(2):1256-1265. · 6.73 Impact Factor
  • T. Yaqoob, K. D. Murphy, L. Miller, T. J. Turner
    Monthly Notices of The Royal Astronomical Society - MON NOTIC ROY ASTRON SOC. 01/2010; 401(1):411-417.
  • Tahir Yaqoob, K. Murphy
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    ABSTRACT: Obscured AGN are now recognized as playing a major role in the population of accreting supermassive black holes and contributing to the Cosmic X-ray Background (CXRB). A "missing" Compton-thick population was expected to emerge from hard (>10 keV) X-ray surveys such as those performed by the Swift BAT and INTEGRAL but these heavily obscured AGN remain elusive and their contribution to the CXRB is still uncertain. We present new results from theoretical calculations that show that hard X-ray surveys are biased againt obscured AGN even when the obscuration is not Compton-thick. We also show that the same material responsible for obscuration in AGN, when viewed thorough non-intercepting lines of sight, can enhance the apparent luminosity by more than 40% when the Compton depth is >1. Thus, even hard X-ray imaging surveys such as those planned with NuSTAR and Astro-H will be more sensitive to Compton-thick UNOBSCURED AGN than Compton-thick obscured AGN by at least an order of magnitude (for NH=1025 cm-2).
    01/2010;
  • Tahir Yaqoob, Kendrah Murphy
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    ABSTRACT: Obscured AGN are now recognized as playing a major role in the population of accreting supermassive black holes. We present new results from theoretical calculations that reveal some rather surprising characteristics of Compton-thick AGN. Our findings have a direct impact on the interpretation of existing data, as well as data from the upcoming missions NuSTAR and Astro-H. We show calculations of the dependence of the Fe K line EW, flux, and observed to intrinsic continuum luminosity ratios on the reprocessor column density, geometry, and orientation. We find that, whilst a large EW Fe K emission line is traditionally thought to be a hallmark for identifying Compton-thick AGN, there is a large part of parameter space in which the Fe K line may not even be detectable due to a small EW. We also show that the soft and hard reprocessed X-ray continua differ significantly from those based on models that are currently used to deduce column density distributions of AGN found in surveys, such as those with Chandra, XMM, and the Swift-BAT. The origin of the differences can be attributed to the inclusion of more realistic assumptions in our models compared to those currently in use. These results also impact synthesis models of the CXRB since our model can be used to derive more realistic column density distributions for AGN. The intrinsic continuum luminosity in Compton-thick AGN is a critical quantity that cannot be directly measured and there is no proxy for estimating it in a trivial manner. However, we show how a robust lower limit on the intrinsic luminosity may be inferred. When applied to Swift-BAT AGN, our calculations show that the BAT survey is actually more biased towards Compton-thick type 1 AGN than Compton-thin type 2 OR type 1 AGN.
    09/2009;
  • Kendrah Murphy, Tahir Yaqoob
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    ABSTRACT: New theoretical model results for Compton-thick reprocessors show that the effects of geometry on the X-ray spectra of AGN are large enough that constraints from real data are possible. Signatures of absorption and Compton scattering of high-energy photons in circumnuclear material, which are critically dependent on the geometry and structure of the reprocessor, are evident in the X-ray spectra of a variety of AGN. However, in order to derive robust constraints from the data, one must model the reflection continuum and line emission self-consistently. The results from our model now allow us to extract such information from high-resolution X-ray data. We show that the X-ray reflection continuum, in addition to being highly sensitive to the column density of the reprocessor and to inclination angle effects, has a dramatic dependence on the geometry of the reprocessor that has hitherto been unexploited. We highlight, in particular, the observable differences between a reflection continuum arising from a toroidal geometry and that resulting from a disk. The equivalent width of the Fe K line core, as well as the detailed shape and relative magnitude of its Compton shoulder, prove to be additional, important diagnostics of the geometry, column density, and inclination of the structure. The velocity width of the Fe K line core has the potential to reveal the spatial location of the reprocessor. However, we emphasize that the velocity width can only be accurately measured if the continuum emission and the Compton shoulder are accounted for with an appropriate model that accommodates a range of geometrical configurations. We demonstrate that new information may be deduced from current data with the application of our Compton-thick reprocessor model. We discuss further insights into AGN systems that will be made possible through measurement and modeling of relevant spectral features with future high-resolution, high-throughput spectroscopic instruments.
    09/2009;
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    Kendrah D. Murphy, Tahir Yaqoob
    [Show abstract] [Hide abstract]
    ABSTRACT: The central engines of both type 1 and type 2 active galactic nuclei are thought to harbour a toroidal structure that absorbs and reprocesses high-energy photons from the central X-ray source. Unique features in the reprocessed spectra can provide powerful physical constraints on the geometry, column density, element abundances and orientation of the circumnuclear matter. If the reprocessor is Compton-thick, the calculation of emission-line and continuum spectra that are suitable for direct fitting to X-ray data is challenging because the reprocessed emission depends on the spectral shape of the incident continuum, which may not be directly observable. We present new Monte Carlo calculations of Green's functions for a toroidal reprocessor that provide significant improvements over currently available models. The Green's function approach enables the construction of X-ray spectral fitting models that allow arbitrary incident spectra as part of the fitting process. The calculations are fully relativistic and have been performed for column densities that cover the Compton-thin to Compton-thick regime, for incident photon energies up to 500 keV. The Green's function library can easily be extended cumulatively to provide models that are valid for higher input energies and a wider range of element abundances and opening angles of the torus. The reprocessed continuum and fluorescent line emission due to Fe Kα, Fe Kβ and Ni Kα are treated self-consistently, eliminating the need for ad hoc modelling that is currently common practice. We find that the spectral shape of the Compton-thick reflection spectrum in both the soft and hard X-ray bands in our toroidal geometry is different compared with that obtained from disc models. A key result of our study is that a Compton-thick toroidal structure that subtends the same solid angle at the X-ray source as a disc can produce a reflection spectrum that is ∼6 times weaker than that from a disc. This highlights the widespread and erroneous interpretation of the so-called ‘reflection-fraction’ as a solid angle, obtained from fitting disc-reflection models to Compton-thick sources without regard for proper consideration of geometry.
    Monthly Notices of the Royal Astronomical Society 08/2009; 397(3):1549 - 1562. · 5.52 Impact Factor
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    K. D. Murphy, T. Yaqoob, M. Dovčiak, V. Karas
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    ABSTRACT: Future X-ray instrumentation is expected to allow us to significantly improve the constraints derivedfrom the Fe K lines in AGN, such as the black-hole angular momentum (spin) and the inclination angle of the putative accretion disk. We consider the possibility that measurements of the persistent, time-averaged Fe K line emission from the disk could be supplemented by the observation of a localized flare, or "hotspot", orbiting close to the black hole. Although observationally challenging, such measurements would recover some of the information loss that is inherent to the radially-integrated line profiles. We present calculations for this scenario to assess the extent to which, in principle, black-hole spin may be measured. We quantify the feasibility of this approach using realistic assumptions about likely measurement uncertainties. Comment: 7 pages, 7 figures. Accepted for publication in ApJ
    The Astrophysical Journal 06/2009; · 6.73 Impact Factor
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    ABSTRACT: We present new Suzaku XIS+HXD data from an observation of 3C 273. A significant but weak Fe K emission line is detected, consistent with historical X-ray observations going back to Ginga. The line is centered around 6.6 keV, indicating an origin in ionized Fe. The continuum measured by the XIS+HXD, however, shows very litte deviation from a power law, consistent with BeppoSAX MECS+PDS data. We discuss the implied constraints on beaming of the X-ray continuum and on the ionization state of the putative accretion disk and the associated reflection continuum. Historically, 3C 273 shows a variable ratio of jet-like and Seyfert-like X-ray continua, the former dominating high flux states, which we show is consistent with 2cm radio monitoring (Mojave Project). The Suzaku data are also useful for assessing the broadband relative calibration of the XIS units and the HXD. We compare the 3C 273 results with those from two contrasting AGN observed by Suzaku: (1) the bright, z=2.172 blazar S 0836+714 (which has a very flat power law with no reflection continuum), and (2) the Seyfert galaxy MCG -6-30-15 which shows a strong reflection continuum that changed in magnitude relative to the direct continuum between two Suzaku epochs.
    03/2008;
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    ABSTRACT: Future X-ray instrumentation is expected to allow us to significantly improve the constraints derived from the Fe K lines in AGN, such as the black-hole angular momentum (spin) and the inclination angle of the putative accretion disk. However, there is some degree of model dependence and degeneracy of physical parameters derived from the radially-integrated, timeaveraged, relativistically broadened components of the Fe K line emission that will persist despite the expected improvements in instrumentation. In particular, the emissivity of the Fe K line as a function of radial position on the accretion disk is unknown and introduces degeneracy in the derived parameters, as does the unknown ionization state of Fe in the disk. Compounding the degeneracy is the fact that, for the majority of AGN, a significant fraction of the Fe K line emission does not originate in the disk, but in distant matter. To derive meaningful constraints from data, one must fit the different convolved line components as well as multiple reflection continua, a process that can be rather ad-hoc. To that end we describe a new X-ray spectral-fitting tool that will allow one to self-consistently fit for the line emission from distant matter as well as for the associated Compton-reflection continuum. The model will allow an arbitrary incident spectrum (up to about 1 MeV) to be part of the fit, and will be valid for a large range of column densities that cover the Compton-thick regime. This model can then be combined with models of relativistic broadening of the disk emission and reflection components to comprehensively fit the broadband spectra of AGN. We then consider the possibility that these measurements of the persistent, time-averaged Fe K line emission from the disk could be supplemented by the observation of a localized flare, or 'hotspot', orbiting close to the black hole. Since time-resolved spectroscopy of the flaring Fe K line emission would not involve the unknown form of the line radial emissivity function, it could potentially provide robust, model-independent information on the black-hole spin. Although observationally challenging, such measurements would recover some of the information loss that is inherent to the radiallyintegrated line profiles. We present calculations for this scenario which represent the best-case model-independent measurement of the black-hole spin that is achievable in principle. We quantify the feasibility of this approach using realistic assumptions about likely measurement uncertainties.
    01/2008;
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    ABSTRACT: Suzaku observations of over 50 AGN are now public and over half of these have noncontemporaneous BeppoSAX data that are highly complementary to the Suzaku data. Suzaku has broadband spectral coverage from 0.5 keV up to tens of keV, combined with the good resolving power and high throughput of the XIS CCD detectors. The Suzaku mission is highly optimized to simultaneously measure the line-of-sight absorption, the Compton-reflection continuum, and Fe K emission and absorption features in celestial X-ray sources. We present some highlights of results from Suzaku observations of AGN as they pertain to providing improved constraints on the putative accreting black-hole systems and their environment. Improved data demand improved modeling and we breifly describe a suite of spectral-fitting routines that address this challenge. The fitting tools not only model relativistic Fe K line emission and continuum re- flection from an accretion disk (with the black-hole spin allowed to be a free parameter), but also self-consistently model the Compton-reflection continuum and the Fe K line emission from distant matter (such as a parsec-scale torus), even when it is Compton thick.
    01/2008;
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    Kendrah D. Murphy, Tahir Yaqoob, Yuichi Terashima
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    ABSTRACT: We present the results of a one year monitoring campaign of the Seyfert 1.9 galaxy NGC 2992 with RXTE. Historically, the source has been shown to vary dramatically in 2-10 keV flux over timescales of years and was thought to be slowly transitioning between periods of quiescence and active accretion. Our results show that in one year the source continuum flux covered almost the entire historical range, making it unlikely that the low-luminosity states correspond to the accretion mechanism switching off. During flaring episodes we found that a highly redshifted Fe K line appears, implying that the violent activity is occurring in the inner accretion disk, within ~100 gravitational radii of the central black hole. We also found that the spectral index of the X-ray continuum remained approximately constant during the large amplitude variability. These observations make NGC 2992 well-suited for future multi-waveband monitoring, as a test-bed for constraining accretion models. Comment: Abstract is abridged. Accepted for publication in the September 2007 issue of ApJ. 39 pages, 14 figures, 3 tables
    The Astrophysical Journal 05/2007; · 6.73 Impact Factor
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    Tahir Yaqoob, Kendrah D. Murphy, Yuichi Terashima
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    ABSTRACT: The Seyfert 1.9 galaxy NGC 2992 has been observed by all X-ray astronomy missions since HEAO-1 for over a quarter of a century, including a one-year RXTE monitoring campaign in 2005/2006 and three Suzaku observations in 2005. The source exhibited over a factor of 20 variability in the hard X-ray luminosity over the ˜25 year period and over an order-of-magnitude variability in the luminosity during the RXTE monitoring period. The luminosity changes are accompanied by spectral variability. In particular there is complex variability in the Fe K emission-line profile which consists of an accretion-disk component and a distant-matter component. The relativistic disk line component shows variability that likely corresponds to changes in the spatial illumination of the disk and the Suzaku data are able to decouple the disk line component from the distant-matter component. In one of the historical BeppoSAX observations an emission-line component from highly ionized Fe was also apparent. In this contribution we illustrate how the unique X-ray properties of NGC 2992 make it one of best supermassive black-hole candidates for testing accretion disk theories since any model must be able to satisfy all of the short and long timescale observational constraints. Future observations need to be planned to exploit the rich behavior to provide even more stringent constraints. NGC 2992 is also a good candidate for constraining AGN unification models.
    Proceedings of the International Astronomical Union 01/2007; 238:123-126.
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    ABSTRACT: We present detailed time-averaged X-ray spectroscopy in the 0.5-10keV band of the Seyfert 1.9 galaxy NGC 2992 with the Suzaku X-ray Imaging Spectrometer (XIS). There is an Fe K line emission complex that we model with broad and narrow lines and we show that the intensities of the two components are decoupled at a confidence level >3σ The broad line (EW = 118-61+32eV) could originate in an accretion disk (inclined at > 30°). The narrow Fe Kα line (EW = 163-26+47eV) is unresolved by the XIS at 99% confidence and likely originates in distant matter. A significant (narrow) Fe Kβ line is also detected and we describe a new robust method to constrain the ionization state of Fe in the distant line emitter (e.g. the putative obscuring torus). The method does not require any knowledge of possible gravitational and Doppler energy shifts and we deduce that the predominant ionization state of Fe in the distant matter is lower than Fe VIII (at 99% confidence), conservatively taking into account residual calibration uncertainties and theoretical and experimental uncertainties in the Fe K fluorescent line energies. We argue that the narrow Fe Kα and Fe Kβ lines likely originate in a Compton-thin structure.
    Publications- Astronomical Society of Japan 12/2006; 59:283-299. · 2.44 Impact Factor
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    ABSTRACT: We present detailed time-averaged X-ray spectroscopy in the 0.5--10 keV band of the Seyfert~1.9 galaxy NGC 2992 with the Suzaku X-ray Imaging Spectrometers (XIS). We model the complex continuum in detail. There is an Fe K line emission complex that we model with broad and narrow lines and we show that the intensities of the two components are decoupled at a confidence level >3sigma. The broad Fe K line has an EW of 118 (+32,-61) eV and could originate in an accretion disk (with inclination angle greater than ~30 degrees). The narrow Fe Kalpha line has an EW of 163 (+47,-26) eV and is unresolved FWHM <4090 km/s) and likely originates in distant matter. The absolute flux in the narrow line implies that the column density out of the line-of-sight could be much higher than measured in the line-of-sight, and that the mean (historically-averaged) continuum luminosity responsible for forming the line could be a factor of several higher than that measured from the data. We also detect the narrow Fe Kbeta line with a high signal-to-noise ratio and describe a new robust method to constrain the ionization state of Fe responsible for the Fe Kalpha and Fe Kbeta lines that does not require any knowledge of possible gravitational and Doppler energy shifts affecting the line energies. For the distant line-emitting matter (e.g. the putative obscuring torus) we deduce that the predominant ionization state is lower than Fe VIII (at 99% confidence), conservatively taking into account residual calibration uncertainties in the XIS energy scale and theoretical and experimental uncertainties in the Fe K fluorescent line energies. From the limits on a possible Compton-reflection continuum it is likely that the narrow Fe Kalpha and Fe Kbeta lines originate in a Compton-thin structure.
    10/2006;