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Tahir Yaqoob - One of the best experts on this subject based on the ideXlab platform.
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the xmm newton iron Line Profile of ngc 3783
The Astrophysical Journal, 2004Co-Authors: J N Reeves, T. J. Turner, K Nandra, I M George, K A Pounds, Tahir YaqoobAbstract:We report on observations of the iron K Line in the nearby Seyfert 1 galaxy, NGC 3783, obtained in a long, two- orbit (� 240 ks) XMM-Newton observation. The Line Profile obtained exhibits two strong narrow peaks at 6.4 and 7.0 keV, with measured Line equivalent widths of 120 and 35 eV, respectively. The 6.4 keVemission is the KLine from near neutral Fe, while the 7.0 keV feature probably originates from a blend of the neutral Fe KLine and the hydrogen-like Line of Fe at 6.97 keV. The relatively narrow velocity width of the KLine (P5000 km s � 1 ), its lack of response to the continuum emission on short timescales, and the detection of a neutral Compton reflection component are all consistent with a distant origin in Compton-thick matter such as the putative molecular torus. A strong absorption Line from highly ionized iron (at 6.67 keV) is detected in the time-averaged iron Line Profile, while the depth of the feature appears to vary with time, being strongest when the continuum flux is higher. The iron absorption Line probably arises from the highest ionization component of the known warm absorber in NGC 3783, with an ionization of log � � 3 and column density of NH � 5 � 10 22 cm � 2 and may originate from within 0.1 pc of the nucleus. Aweak red wing to the iron K Line Profile is also detected below 6.4 keV. However, when the effect of the highly ionized warm absorber on the underlying continuum is taken into account, the requirement for a relativistic iron Line component from the inner disk is reduced. Subject headings: galaxies: active — galaxies: individual (NGC 3783) — galaxies: Seyfert — X-rays: galaxies
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the xmm newton iron Line Profile of ngc 3783
arXiv: Astrophysics, 2003Co-Authors: J N Reeves, T. J. Turner, K Nandra, I M George, K A Pounds, Tahir YaqoobAbstract:We report on observations of the iron K Line in the nearby Seyfert 1 galaxy, NGC 3783, obtained in a long, 2 orbit (240 ks) XMM-Newton observation. The Line Profile obtained exhibits two strong narrow peaks at 6.4 keV and at 7.0 keV, with measured Line equivalent widths of 120 and 35 eV respectively. The 6.4 keV emission is the K-alpha Line from near neutral Fe, whilst the 7.0 keV feature probably originates from a blend of the neutral Fe K-beta Line and the H-like Line of Fe at 6.97 keV. The relatively narrow velocity width of the K-alpha Line (<5000 km/s), its lack of response to the continuum emission on short timescales and the detection of a neutral Compton reflection component are all consistent with a distant origin in Compton-thick matter such as the putative molecular torus. A strong absorption Line from highly ionized iron (at 6.67 keV) is detected in the time-averaged iron Line Profile, whilst the depth of the feature appears to vary with time, being strongest when the continuum flux is higher. The iron absorption Line probably arises from the highest ionization component of the known warm absorber in NGC 3783, with an ionization of logxi=3 and column density of 5x10^{22}cm{-2} and may originate from within 0.1pc of the nucleus. A weak red-wing to the iron K Line Profile is also detected below 6.4 keV. However when the effect of the highly ionized warm absorber on the underlying continuum is taken into account, the requirement for a relativistic iron Line component from the inner disk is reduced.
J N Reeves - One of the best experts on this subject based on the ideXlab platform.
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An Extreme, Blueshifted Iron‐Line Profile in the Narrow‐Line Seyfert 1 PG 1402+261: An Edge‐on Accretion Disk or Highly Ionized Absorption?
The Astrophysical Journal, 2004Co-Authors: J N Reeves, D. Porquet, T. J. TurnerAbstract:We report on a short XMM-Newton observation of the radio-quiet narrow-Line Seyfert 1 galaxy PG 1402+261. The EPIC X-ray spectrum of PG 1402+261 shows a strong excess of counts between 6 and 9 keV in the rest frame. This feature can be modeled by an unusually strong (equivalent width 2 keV) and very broad (FWHM velocity of 110,000 km s-1) iron K-shell emission Line. The Line centroid energy at 7.3 keV appears blueshifted with respect to the iron Kα emission band between 6.4 and 6.97 keV, while the blue wing of the Line extends to 9 keV in the quasar rest frame. The Line Profile can be fitted by reflection from the inner accretion disk, but an inclination angle of >60° is required to model the extreme blue wing of the Line. Furthermore, the extreme strength of the Line requires a geometry whereby the hard X-ray emission from PG 1402+261 above 2 keV is dominated by the pure-reflection component from the disk, while little or none of the direct hard power law is observed. Alternatively, the spectrum above 2 keV may be explained by an ionized absorber, if the column density is sufficiently high (NH>3×1023 cm-2) and if the matter is ionized enough to produce a deep (τ~1) iron K-shell absorption edge at 9 keV. This absorber could originate in a large column density, high-velocity outflow, perhaps similar to those that appear to be observed in several other high accretion rate active galactic nuclei. Further observations, especially at higher spectral resolution, are required to distinguish between the accretion disk reflection and outflow scenarios.
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the xmm newton iron Line Profile of ngc 3783
The Astrophysical Journal, 2004Co-Authors: J N Reeves, T. J. Turner, K Nandra, I M George, K A Pounds, Tahir YaqoobAbstract:We report on observations of the iron K Line in the nearby Seyfert 1 galaxy, NGC 3783, obtained in a long, two- orbit (� 240 ks) XMM-Newton observation. The Line Profile obtained exhibits two strong narrow peaks at 6.4 and 7.0 keV, with measured Line equivalent widths of 120 and 35 eV, respectively. The 6.4 keVemission is the KLine from near neutral Fe, while the 7.0 keV feature probably originates from a blend of the neutral Fe KLine and the hydrogen-like Line of Fe at 6.97 keV. The relatively narrow velocity width of the KLine (P5000 km s � 1 ), its lack of response to the continuum emission on short timescales, and the detection of a neutral Compton reflection component are all consistent with a distant origin in Compton-thick matter such as the putative molecular torus. A strong absorption Line from highly ionized iron (at 6.67 keV) is detected in the time-averaged iron Line Profile, while the depth of the feature appears to vary with time, being strongest when the continuum flux is higher. The iron absorption Line probably arises from the highest ionization component of the known warm absorber in NGC 3783, with an ionization of log � � 3 and column density of NH � 5 � 10 22 cm � 2 and may originate from within 0.1 pc of the nucleus. Aweak red wing to the iron K Line Profile is also detected below 6.4 keV. However, when the effect of the highly ionized warm absorber on the underlying continuum is taken into account, the requirement for a relativistic iron Line component from the inner disk is reduced. Subject headings: galaxies: active — galaxies: individual (NGC 3783) — galaxies: Seyfert — X-rays: galaxies
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the xmm newton iron Line Profile of ngc 3783
arXiv: Astrophysics, 2003Co-Authors: J N Reeves, T. J. Turner, K Nandra, I M George, K A Pounds, Tahir YaqoobAbstract:We report on observations of the iron K Line in the nearby Seyfert 1 galaxy, NGC 3783, obtained in a long, 2 orbit (240 ks) XMM-Newton observation. The Line Profile obtained exhibits two strong narrow peaks at 6.4 keV and at 7.0 keV, with measured Line equivalent widths of 120 and 35 eV respectively. The 6.4 keV emission is the K-alpha Line from near neutral Fe, whilst the 7.0 keV feature probably originates from a blend of the neutral Fe K-beta Line and the H-like Line of Fe at 6.97 keV. The relatively narrow velocity width of the K-alpha Line (<5000 km/s), its lack of response to the continuum emission on short timescales and the detection of a neutral Compton reflection component are all consistent with a distant origin in Compton-thick matter such as the putative molecular torus. A strong absorption Line from highly ionized iron (at 6.67 keV) is detected in the time-averaged iron Line Profile, whilst the depth of the feature appears to vary with time, being strongest when the continuum flux is higher. The iron absorption Line probably arises from the highest ionization component of the known warm absorber in NGC 3783, with an ionization of logxi=3 and column density of 5x10^{22}cm{-2} and may originate from within 0.1pc of the nucleus. A weak red-wing to the iron K Line Profile is also detected below 6.4 keV. However when the effect of the highly ionized warm absorber on the underlying continuum is taken into account, the requirement for a relativistic iron Line component from the inner disk is reduced.
C. Aerts - One of the best experts on this subject based on the ideXlab platform.
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on the use of the fourier transform to determine the projected rotational velocity of Line Profile variable b stars
Astronomy and Astrophysics, 2014Co-Authors: C. Aerts, S Simondiaz, P J Groot, P DegrooteAbstract:Context. The Fourier transform method is a popular tool for deriving the rotational velocities of stars from their spectral Line Profiles. However, its domain of validity does not include Line-Profile variables with time-dependent Profiles. Aims. We investigate the performance of the method for such cases, by interpreting the Line-Profile variations of spotted B stars and of pulsating B stars, as if their spectral Lines were caused by uniform surface rotation along with macroturbulence. Methods. We perform time-series analysis and harmonic least-squares fitting of various Line diagnostics and of the outcome of several implementations of the Fourier transform method. Results. We find that the projected rotational velocities derived from the Fourier transform vary appreciably during the pulsation cycle whenever the pulsational and rotational velocity fields have similar magnitudes. The macroturbulent velocities derived while ignoring the pulsations can vary by tens of km s −1 during the pulsation cycle. The temporal behaviour of the deduced rotational and macroturbulent velocities are in antiphase with each other. The rotational velocity is in phase with the second moment of the Line Profiles. Conclusions. The application of the Fourier method to stars with considerable pulsational Line broadening may lead to an appreciable spread in the values of the rotation velocity, and, by implication, of the deduced value of the macroturbulence. These two quantities should therefore not be derived from single snapshot spectra if the aim is to use them as a solid diagnostic evaluating stellar evolution models of slow-to-moderate rotators.
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on the use of the fourier transform to determine the projected rotational velocity of Line Profile variable b stars
arXiv: Solar and Stellar Astrophysics, 2014Co-Authors: C. Aerts, S Simondiaz, P J Groot, P DegrooteAbstract:The Fourier Transform method is a popular tool to derive the rotational velocities of stars from their spectral Line Profiles. However, its domain of validity does not include Line-Profile variables with time-dependent Profiles. We investigate the performance of the method for such cases, by interpreting the Line-Profile variations of spotted B stars, and of pulsating B tars, as if their spectral Lines were caused by uniform surface rotation along with macroturbulence. We perform time-series analysis and harmonic least-squares fitting of various Line diagnostics and of the outcome of several implementations of the Fourier Transform method. We find that the projected rotational velocities derived from the Fourier Transform vary appreciably during the pulsation cycle whenever the pulsational and rotational velocity fields are of similar magnitude. The macroturbulent velocities derived while ignoring the pulsations can vary with tens of km/s during the pulsation cycle. The temporal behaviour of the deduced rotational and macroturbulent velocities are in antiphase with each other. The rotational velocity is in phase with the second moment of the Line Profiles. The application of the Fourier method to stars with considerable pulsational Line broadening may lead to an appreciable spread in the values of the rotation velocity, and, by implication, of the deduced value of the macroturbulence. These two quantities should therefore not be derived from single snapshot spectra if the aim is to use them as a solid diagnostic for the evaluation of stellar evolution models of slow to moderate rotators.
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observational evidence for a correlation between macroturbulent broadening and Line Profile variations in ob supergiants
The Astrophysical Journal, 2010Co-Authors: C. Aerts, S Simondiaz, A Herrero, K Uytterhoeven, N Castro, J PulsAbstract:The spectra of O and B supergiants (Sgs) are known to be affected by a significant form of extra Line broadening (usually referred to as macroturbulence) in addition to that produced by stellar rotation. Recent analyses of high-resolution spectra have shown that the interpretation of this Line broadening as a consequence of large-scale turbulent motions would imply highly supersonic velocity fields in photospheric regions, making this scenario quite improbable. Stellar oscillations have been proposed as a likely alternative explanation. As part of a long-term observational project, we are investigating the macroturbulent broadening in O and B Sgs and its possible connection with spectroscopic variability phenomena and stellar oscillations. In this Letter, we present the first encouraging results of our project, namely, firm observational evidence for a strong correlation between the extra broadening and photospheric Line-Profile variations in a sample of 13 Sgs with spectral types ranging from O9.5 to B8.
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observational evidence for a correlation between macroturbulent broadening and Line Profile variations in ob supergiants
arXiv: Solar and Stellar Astrophysics, 2010Co-Authors: C. Aerts, S Simondiaz, A Herrero, K Uytterhoeven, N Castro, J PulsAbstract:The spectra of O and B supergiants are known to be affected by a significant form of extra Line broadening (usually referred to as macroturbulence) in addition to that produced by stellar rotation. Recent analyses of high resolution spectra have shown that the interpretation of this Line broadening as a consequence of large scale turbulent motions would imply highly supersonic velocity fields in photospheric regions, making this scenario quite improbable. Stellar oscillations have been proposed as a likely alternative explanation. As part of a long term observational project, we are investigating the macroturbulent broadening in O and B supergiants and its possible connection with spectroscopic variability phenomena and stellar oscillations. In this letter, we present the first encouraging results of our project, namely firm observational evidence for a strong correlation between the extra broadening and photospheric Line-Profile variations in a sample of 13 supergiants with spectral types ranging from O9.5 to B8.
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Line-Profile variability in the βCephei starCentauri
2004Co-Authors: C. Schrijvers, J.h. Telting, C. AertsAbstract:We present an analysis of 530 high-resolution spectra of the β Cephei starCen, showing complex variations in the rotationally broadened absorption Line-Profiles of the Si triplet (λ 4552, 4567, 4574 A). Most data were acquired during four dedicated observing runs between April 1996 and June 1998, with time spans between 6 and 14 days. We calculate velocity moments of the Line Profiles and apply Fourier analysis techniques to analyze their time behavior. The variations of the velocity moments confirm the presence of two periods already known from photometry, and provide evidence for the presence of two or more non-radial pulsation modes. Our analysis of the spectral time series concentrates on the variability at each position in the λ 4567 A Line Profile. In addition to the two frequencies found in the radial-velocity variations, we find several other periodicities to be present across the Line Profile. We use Fourier analysis, sinusoid fitting, and folding techniques to analyze the amplitude and phase information for each of the detected periods. We find evidence for at least five pulsation modes inCen, and identify � -values between 2 and 5.
S Simondiaz - One of the best experts on this subject based on the ideXlab platform.
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on the use of the fourier transform to determine the projected rotational velocity of Line Profile variable b stars
Astronomy and Astrophysics, 2014Co-Authors: C. Aerts, S Simondiaz, P J Groot, P DegrooteAbstract:Context. The Fourier transform method is a popular tool for deriving the rotational velocities of stars from their spectral Line Profiles. However, its domain of validity does not include Line-Profile variables with time-dependent Profiles. Aims. We investigate the performance of the method for such cases, by interpreting the Line-Profile variations of spotted B stars and of pulsating B stars, as if their spectral Lines were caused by uniform surface rotation along with macroturbulence. Methods. We perform time-series analysis and harmonic least-squares fitting of various Line diagnostics and of the outcome of several implementations of the Fourier transform method. Results. We find that the projected rotational velocities derived from the Fourier transform vary appreciably during the pulsation cycle whenever the pulsational and rotational velocity fields have similar magnitudes. The macroturbulent velocities derived while ignoring the pulsations can vary by tens of km s −1 during the pulsation cycle. The temporal behaviour of the deduced rotational and macroturbulent velocities are in antiphase with each other. The rotational velocity is in phase with the second moment of the Line Profiles. Conclusions. The application of the Fourier method to stars with considerable pulsational Line broadening may lead to an appreciable spread in the values of the rotation velocity, and, by implication, of the deduced value of the macroturbulence. These two quantities should therefore not be derived from single snapshot spectra if the aim is to use them as a solid diagnostic evaluating stellar evolution models of slow-to-moderate rotators.
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on the use of the fourier transform to determine the projected rotational velocity of Line Profile variable b stars
arXiv: Solar and Stellar Astrophysics, 2014Co-Authors: C. Aerts, S Simondiaz, P J Groot, P DegrooteAbstract:The Fourier Transform method is a popular tool to derive the rotational velocities of stars from their spectral Line Profiles. However, its domain of validity does not include Line-Profile variables with time-dependent Profiles. We investigate the performance of the method for such cases, by interpreting the Line-Profile variations of spotted B stars, and of pulsating B tars, as if their spectral Lines were caused by uniform surface rotation along with macroturbulence. We perform time-series analysis and harmonic least-squares fitting of various Line diagnostics and of the outcome of several implementations of the Fourier Transform method. We find that the projected rotational velocities derived from the Fourier Transform vary appreciably during the pulsation cycle whenever the pulsational and rotational velocity fields are of similar magnitude. The macroturbulent velocities derived while ignoring the pulsations can vary with tens of km/s during the pulsation cycle. The temporal behaviour of the deduced rotational and macroturbulent velocities are in antiphase with each other. The rotational velocity is in phase with the second moment of the Line Profiles. The application of the Fourier method to stars with considerable pulsational Line broadening may lead to an appreciable spread in the values of the rotation velocity, and, by implication, of the deduced value of the macroturbulence. These two quantities should therefore not be derived from single snapshot spectra if the aim is to use them as a solid diagnostic for the evaluation of stellar evolution models of slow to moderate rotators.
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observational evidence for a correlation between macroturbulent broadening and Line Profile variations in ob supergiants
The Astrophysical Journal, 2010Co-Authors: C. Aerts, S Simondiaz, A Herrero, K Uytterhoeven, N Castro, J PulsAbstract:The spectra of O and B supergiants (Sgs) are known to be affected by a significant form of extra Line broadening (usually referred to as macroturbulence) in addition to that produced by stellar rotation. Recent analyses of high-resolution spectra have shown that the interpretation of this Line broadening as a consequence of large-scale turbulent motions would imply highly supersonic velocity fields in photospheric regions, making this scenario quite improbable. Stellar oscillations have been proposed as a likely alternative explanation. As part of a long-term observational project, we are investigating the macroturbulent broadening in O and B Sgs and its possible connection with spectroscopic variability phenomena and stellar oscillations. In this Letter, we present the first encouraging results of our project, namely, firm observational evidence for a strong correlation between the extra broadening and photospheric Line-Profile variations in a sample of 13 Sgs with spectral types ranging from O9.5 to B8.
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observational evidence for a correlation between macroturbulent broadening and Line Profile variations in ob supergiants
arXiv: Solar and Stellar Astrophysics, 2010Co-Authors: C. Aerts, S Simondiaz, A Herrero, K Uytterhoeven, N Castro, J PulsAbstract:The spectra of O and B supergiants are known to be affected by a significant form of extra Line broadening (usually referred to as macroturbulence) in addition to that produced by stellar rotation. Recent analyses of high resolution spectra have shown that the interpretation of this Line broadening as a consequence of large scale turbulent motions would imply highly supersonic velocity fields in photospheric regions, making this scenario quite improbable. Stellar oscillations have been proposed as a likely alternative explanation. As part of a long term observational project, we are investigating the macroturbulent broadening in O and B supergiants and its possible connection with spectroscopic variability phenomena and stellar oscillations. In this letter, we present the first encouraging results of our project, namely firm observational evidence for a strong correlation between the extra broadening and photospheric Line-Profile variations in a sample of 13 supergiants with spectral types ranging from O9.5 to B8.
T. J. Turner - One of the best experts on this subject based on the ideXlab platform.
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An Extreme, Blueshifted Iron‐Line Profile in the Narrow‐Line Seyfert 1 PG 1402+261: An Edge‐on Accretion Disk or Highly Ionized Absorption?
The Astrophysical Journal, 2004Co-Authors: J N Reeves, D. Porquet, T. J. TurnerAbstract:We report on a short XMM-Newton observation of the radio-quiet narrow-Line Seyfert 1 galaxy PG 1402+261. The EPIC X-ray spectrum of PG 1402+261 shows a strong excess of counts between 6 and 9 keV in the rest frame. This feature can be modeled by an unusually strong (equivalent width 2 keV) and very broad (FWHM velocity of 110,000 km s-1) iron K-shell emission Line. The Line centroid energy at 7.3 keV appears blueshifted with respect to the iron Kα emission band between 6.4 and 6.97 keV, while the blue wing of the Line extends to 9 keV in the quasar rest frame. The Line Profile can be fitted by reflection from the inner accretion disk, but an inclination angle of >60° is required to model the extreme blue wing of the Line. Furthermore, the extreme strength of the Line requires a geometry whereby the hard X-ray emission from PG 1402+261 above 2 keV is dominated by the pure-reflection component from the disk, while little or none of the direct hard power law is observed. Alternatively, the spectrum above 2 keV may be explained by an ionized absorber, if the column density is sufficiently high (NH>3×1023 cm-2) and if the matter is ionized enough to produce a deep (τ~1) iron K-shell absorption edge at 9 keV. This absorber could originate in a large column density, high-velocity outflow, perhaps similar to those that appear to be observed in several other high accretion rate active galactic nuclei. Further observations, especially at higher spectral resolution, are required to distinguish between the accretion disk reflection and outflow scenarios.
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the xmm newton iron Line Profile of ngc 3783
The Astrophysical Journal, 2004Co-Authors: J N Reeves, T. J. Turner, K Nandra, I M George, K A Pounds, Tahir YaqoobAbstract:We report on observations of the iron K Line in the nearby Seyfert 1 galaxy, NGC 3783, obtained in a long, two- orbit (� 240 ks) XMM-Newton observation. The Line Profile obtained exhibits two strong narrow peaks at 6.4 and 7.0 keV, with measured Line equivalent widths of 120 and 35 eV, respectively. The 6.4 keVemission is the KLine from near neutral Fe, while the 7.0 keV feature probably originates from a blend of the neutral Fe KLine and the hydrogen-like Line of Fe at 6.97 keV. The relatively narrow velocity width of the KLine (P5000 km s � 1 ), its lack of response to the continuum emission on short timescales, and the detection of a neutral Compton reflection component are all consistent with a distant origin in Compton-thick matter such as the putative molecular torus. A strong absorption Line from highly ionized iron (at 6.67 keV) is detected in the time-averaged iron Line Profile, while the depth of the feature appears to vary with time, being strongest when the continuum flux is higher. The iron absorption Line probably arises from the highest ionization component of the known warm absorber in NGC 3783, with an ionization of log � � 3 and column density of NH � 5 � 10 22 cm � 2 and may originate from within 0.1 pc of the nucleus. Aweak red wing to the iron K Line Profile is also detected below 6.4 keV. However, when the effect of the highly ionized warm absorber on the underlying continuum is taken into account, the requirement for a relativistic iron Line component from the inner disk is reduced. Subject headings: galaxies: active — galaxies: individual (NGC 3783) — galaxies: Seyfert — X-rays: galaxies
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the xmm newton iron Line Profile of ngc 3783
arXiv: Astrophysics, 2003Co-Authors: J N Reeves, T. J. Turner, K Nandra, I M George, K A Pounds, Tahir YaqoobAbstract:We report on observations of the iron K Line in the nearby Seyfert 1 galaxy, NGC 3783, obtained in a long, 2 orbit (240 ks) XMM-Newton observation. The Line Profile obtained exhibits two strong narrow peaks at 6.4 keV and at 7.0 keV, with measured Line equivalent widths of 120 and 35 eV respectively. The 6.4 keV emission is the K-alpha Line from near neutral Fe, whilst the 7.0 keV feature probably originates from a blend of the neutral Fe K-beta Line and the H-like Line of Fe at 6.97 keV. The relatively narrow velocity width of the K-alpha Line (<5000 km/s), its lack of response to the continuum emission on short timescales and the detection of a neutral Compton reflection component are all consistent with a distant origin in Compton-thick matter such as the putative molecular torus. A strong absorption Line from highly ionized iron (at 6.67 keV) is detected in the time-averaged iron Line Profile, whilst the depth of the feature appears to vary with time, being strongest when the continuum flux is higher. The iron absorption Line probably arises from the highest ionization component of the known warm absorber in NGC 3783, with an ionization of logxi=3 and column density of 5x10^{22}cm{-2} and may originate from within 0.1pc of the nucleus. A weak red-wing to the iron K Line Profile is also detected below 6.4 keV. However when the effect of the highly ionized warm absorber on the underlying continuum is taken into account, the requirement for a relativistic iron Line component from the inner disk is reduced.