The Suzaku view of highly-ionised outflows in AGN: I - Statistical detection and global absorber properties. (arXiv:1211.5810v1 [astro-ph.HE]):
We present the results of a new spectroscopic study of Fe K-band absorption
in Active Galactic Nuclei (AGN). Using data obtained from the Suzaku public
archive we have performed a statistically driven blind search for Fe XXV Hea
and/or Fe XXVI Lyb absorption lines in a large sample of 51 type 1.0-1.9 AGN.
Through extensive Monte Carlo simulations we find statistically significant
absorption is detected at E>6.7 keV in 20/51 sources at the P(MC)>95% level,
which corresponds to ~40% of the total sample. In all cases, individual
absorption lines are detected independently and simultaneously amongst the two
(or three) available XIS detectors which confirms the robustness of the line
detections. The most frequently observed outflow phenomenology consists of two
discrete absorption troughs corresponding to Fe XXV Hea and Fe XXVI Lyb at a
common velocity shift. From xstar fitting the mean column density and
ionisation parameter for the Fe K absorption components are log(NH/cm^{-2})~23
and log(xi/erg cm s^{-1})~4.5, respectively. Measured outflow velocities span a
continuous range from <1,500 km/s up to ~100,000 km/s, with mean and median
values of ~0.1c and ~0.056c, respectively. The results of this work are
consistent with those recently obtained using XMM-Newton and independently
provides strong evidence for the existence of very highly-ionised circumnuclear
material in a significant fraction of both radio-quiet and radio-loud AGN in
the local universe.
Saturday, December 1, 2012
The rapid evolution of AGN feedback in brightest cluster galaxies: switching from quasar-mode to radio-mode feedback. (arXiv:1211.5606v1 [astro-ph.CO])
The rapid evolution of AGN feedback in brightest cluster galaxies: switching from quasar-mode to radio-mode feedback. (arXiv:1211.5606v1 [astro-ph.CO]):
We present an analysis of the 2-10 keV X-ray emission associated with the
active galactic nuclei (AGNs) in brightest cluster galaxies (BCGs). Our sample
consists of 32 BCGs that lie in highly X-ray luminous cluster of galaxies
[L_X-ray(0.1-2.4 keV)>3*10^44 erg/s] in which AGN-jetted outflows are creating
and sustaining clear X-ray cavities. Our sample covers the redshift range
0<z<0.6 and reveals strong evolution in the nuclear X-ray luminosities, such
that the black holes in these systems have become on average at least 10 times
fainter over the last 5 Gyrs. Mindful of the potential selection effects that
may affect our results, we propose two possible scenarios to explain our
results: 1) either that the AGNs in BCGs with X-ray cavities are steadily
becoming fainter, or more likely, 2) that the fraction of these BCGs with
radiatively efficient nuclei is decreasing with time from roughly 60 per cent
at z~0.6 to 30 per cent at z~0.1. Based on this strong evolution, we predict
that a significant fraction of BCGs in z~1 clusters may host quasars at their
centres, potentially complicating the search for such clusters at high
redshift. In analogy with black-hole binaries and based on the observed
Eddington ratios of our sources, we further propose that the evolving AGN
population in BCGs with X-ray cavities may be transiting from a canonical
low/hard state analogous to that of X-ray binaries to a quiescent state over
the last 5 Gyrs.
We present an analysis of the 2-10 keV X-ray emission associated with the
active galactic nuclei (AGNs) in brightest cluster galaxies (BCGs). Our sample
consists of 32 BCGs that lie in highly X-ray luminous cluster of galaxies
[L_X-ray(0.1-2.4 keV)>3*10^44 erg/s] in which AGN-jetted outflows are creating
and sustaining clear X-ray cavities. Our sample covers the redshift range
0<z<0.6 and reveals strong evolution in the nuclear X-ray luminosities, such
that the black holes in these systems have become on average at least 10 times
fainter over the last 5 Gyrs. Mindful of the potential selection effects that
may affect our results, we propose two possible scenarios to explain our
results: 1) either that the AGNs in BCGs with X-ray cavities are steadily
becoming fainter, or more likely, 2) that the fraction of these BCGs with
radiatively efficient nuclei is decreasing with time from roughly 60 per cent
at z~0.6 to 30 per cent at z~0.1. Based on this strong evolution, we predict
that a significant fraction of BCGs in z~1 clusters may host quasars at their
centres, potentially complicating the search for such clusters at high
redshift. In analogy with black-hole binaries and based on the observed
Eddington ratios of our sources, we further propose that the evolving AGN
population in BCGs with X-ray cavities may be transiting from a canonical
low/hard state analogous to that of X-ray binaries to a quiescent state over
the last 5 Gyrs.
Radiative efficiency, variability and Bondi accretion onto massive black holes: from mechanical to quasar feedback in brightest cluster galaxies. (arXiv:1211.5604v1 [astro-ph.CO])
Radiative efficiency, variability and Bondi accretion onto massive black holes: from mechanical to quasar feedback in brightest cluster galaxies. (arXiv:1211.5604v1 [astro-ph.CO]):
We examine unresolved nuclear X-ray sources in 57 brightest cluster galaxies
to study the relationship between nuclear X-ray emission and accretion onto
supermassive black holes (SMBHs). The majority of the clusters in our sample
have prominent X-ray cavities embedded in the surrounding hot atmospheres,
which we use to estimate mean jet power and average accretion rate onto the
SMBHs over the past several hundred Myr. We find that ~50% of the sample have
detectable nuclear X-ray emission. The nuclear X-ray luminosity is correlated
with average accretion rate determined using X-ray cavities, which is
consistent with the hypothesis that nuclear X-ray emission traces ongoing
accretion. The results imply that jets in systems that have experienced recent
AGN outbursts, in the last ~10^7yr, are `on' at least half of the time. Nuclear
X-ray sources become more luminous with respect to the mechanical jet power as
the mean accretion rate rises. We show that nuclear radiation exceeds the jet
power when the mean accretion rate rises above a few percent of the Eddington
rate, where the AGN apparently transitions to a quasar. The nuclear X-ray
emission from three objects (A2052, Hydra A, M84) varies by factors of 2-10 on
timescales of 6 months to 10 years. If variability at this level is a common
phenomenon, it can account for much of the scatter in the relationship between
mean accretion rate and nuclear X-ray luminosity. We find no significant change
in the spectral energy distribution as a function of luminosity in the variable
objects. The relationship between accretion and nuclear X-ray luminosity is
consistent with emission from either a jet, an ADAF, or a combination of the
two, although other origins are possible. We also consider the longstanding
problem of whether jets are powered by the accretion of cold circumnuclear gas
or nearly spherical inflows of hot keV gas.[abridged]
We examine unresolved nuclear X-ray sources in 57 brightest cluster galaxies
to study the relationship between nuclear X-ray emission and accretion onto
supermassive black holes (SMBHs). The majority of the clusters in our sample
have prominent X-ray cavities embedded in the surrounding hot atmospheres,
which we use to estimate mean jet power and average accretion rate onto the
SMBHs over the past several hundred Myr. We find that ~50% of the sample have
detectable nuclear X-ray emission. The nuclear X-ray luminosity is correlated
with average accretion rate determined using X-ray cavities, which is
consistent with the hypothesis that nuclear X-ray emission traces ongoing
accretion. The results imply that jets in systems that have experienced recent
AGN outbursts, in the last ~10^7yr, are `on' at least half of the time. Nuclear
X-ray sources become more luminous with respect to the mechanical jet power as
the mean accretion rate rises. We show that nuclear radiation exceeds the jet
power when the mean accretion rate rises above a few percent of the Eddington
rate, where the AGN apparently transitions to a quasar. The nuclear X-ray
emission from three objects (A2052, Hydra A, M84) varies by factors of 2-10 on
timescales of 6 months to 10 years. If variability at this level is a common
phenomenon, it can account for much of the scatter in the relationship between
mean accretion rate and nuclear X-ray luminosity. We find no significant change
in the spectral energy distribution as a function of luminosity in the variable
objects. The relationship between accretion and nuclear X-ray luminosity is
consistent with emission from either a jet, an ADAF, or a combination of the
two, although other origins are possible. We also consider the longstanding
problem of whether jets are powered by the accretion of cold circumnuclear gas
or nearly spherical inflows of hot keV gas.[abridged]
Major contributor to AGN feedback: VLT X-shooter observations of SIV BAL QSO outflows. (arXiv:1211.6250v1 [astro-ph.CO])
Major contributor to AGN feedback: VLT X-shooter observations of SIV BAL QSO outflows. (arXiv:1211.6250v1 [astro-ph.CO]):
We present the most energetic BALQSO outflow measured to date, with a kinetic
luminosity of at least 10^46 ergs/s, which is 5% of the bolometric luminosity
of this high Eddington ratio quasar. The associated mass flow rate is 400 solar
masses per year. Such kinetic luminosity and mass flow rate should provide
strong AGN feedback effects. The outflow is located at about 300 pc from the
quasar and has a velocity of roughly 8000 km/s. Our distance and energetic
measurements are based in large part on the identification and measurement of
SIV and SIV* BALs. The use of this high ionization species allows us to
generalize the result to the majority of high ionization BALQSOs that are
identified by their CIV absorption. We also report the energetics of two other
outflows seen in another object using the same technique. The distances of all
3 outflows from the central source (100-2000pc) suggest that we observe BAL
troughs much farther away from the central source than the assumed acceleration
region of these outflows (0.01-0.1pc).
We present the most energetic BALQSO outflow measured to date, with a kinetic
luminosity of at least 10^46 ergs/s, which is 5% of the bolometric luminosity
of this high Eddington ratio quasar. The associated mass flow rate is 400 solar
masses per year. Such kinetic luminosity and mass flow rate should provide
strong AGN feedback effects. The outflow is located at about 300 pc from the
quasar and has a velocity of roughly 8000 km/s. Our distance and energetic
measurements are based in large part on the identification and measurement of
SIV and SIV* BALs. The use of this high ionization species allows us to
generalize the result to the majority of high ionization BALQSOs that are
identified by their CIV absorption. We also report the energetics of two other
outflows seen in another object using the same technique. The distances of all
3 outflows from the central source (100-2000pc) suggest that we observe BAL
troughs much farther away from the central source than the assumed acceleration
region of these outflows (0.01-0.1pc).
Hydrodynamic Studies of the Evolution of Recurrent, Symbiotic, and Dwarf Novae: The White Dwarf Components are Growing in Mass. (arXiv:1211.6145v1 [astro-ph.SR])
Hydrodynamic Studies of the Evolution of Recurrent, Symbiotic, and Dwarf Novae: The White Dwarf Components are Growing in Mass. (arXiv:1211.6145v1 [astro-ph.SR]):
Symbiotic binaries are systems containing white dwarfs (WDs) and red giants.
Symbiotic novae are those systems in which thermonuclear eruptions occur on the
WD components. These are to be distinguished from events driven by accretion
disk instabilities analogous to dwarf novae eruptions in cataclysmic variable
outbursts. Another class of symbiotic systems are those in which the WD is
extremely luminous and it seems likely that quiescent nuclear burning is
ongoing on the accreting WD. A fundamental question is the secular evolution of
the WD. Do the repeated outbursts or quiescent burning in these accreting
systems cause the WD to gain or lose mass? If it is gaining mass, can it
eventually reach the Chandrasekhar Limit and become a supernova (a SN Ia if it
can hide the hydrogen and helium in the system)? In order to better understand
these systems, we have begun a new study of the evolution of Thermonuclear
Runaways (TNRs) in the accreted envelopes of WDs using a variety of initial WD
masses, luminosities and mass accretion rates. We use our 1-D hydro code, NOVA,
which includes the new convective algorithm of Arnett, Meakin and Young, the
Hix and Thielemann nuclear reaction solver, the Iliadis reaction rate library,
the Timmes equation of state, and the OPAL opacities. We assume a solar
composition (Lodders abundance distribution) and do not allow any mixing of
accreted material with core material. This assumption strongly influences our
results. We report here (1) that the WD grows in mass for all simulations so
that canonical `steady burning' does not occur, and (2) that only a small
fraction of the accreted matter is ejected in some (but not all) simulations.
We also find that the accreting systems, before thermonuclear runaway, are too
cool to be seen in X-ray searches for SN Ia progenitors.
Symbiotic binaries are systems containing white dwarfs (WDs) and red giants.
Symbiotic novae are those systems in which thermonuclear eruptions occur on the
WD components. These are to be distinguished from events driven by accretion
disk instabilities analogous to dwarf novae eruptions in cataclysmic variable
outbursts. Another class of symbiotic systems are those in which the WD is
extremely luminous and it seems likely that quiescent nuclear burning is
ongoing on the accreting WD. A fundamental question is the secular evolution of
the WD. Do the repeated outbursts or quiescent burning in these accreting
systems cause the WD to gain or lose mass? If it is gaining mass, can it
eventually reach the Chandrasekhar Limit and become a supernova (a SN Ia if it
can hide the hydrogen and helium in the system)? In order to better understand
these systems, we have begun a new study of the evolution of Thermonuclear
Runaways (TNRs) in the accreted envelopes of WDs using a variety of initial WD
masses, luminosities and mass accretion rates. We use our 1-D hydro code, NOVA,
which includes the new convective algorithm of Arnett, Meakin and Young, the
Hix and Thielemann nuclear reaction solver, the Iliadis reaction rate library,
the Timmes equation of state, and the OPAL opacities. We assume a solar
composition (Lodders abundance distribution) and do not allow any mixing of
accreted material with core material. This assumption strongly influences our
results. We report here (1) that the WD grows in mass for all simulations so
that canonical `steady burning' does not occur, and (2) that only a small
fraction of the accreted matter is ejected in some (but not all) simulations.
We also find that the accreting systems, before thermonuclear runaway, are too
cool to be seen in X-ray searches for SN Ia progenitors.
The Nearest Millisecond Pulsar Revisited with XMM-Newton: Improved Mass-Radius Constraints for PSR J0437-4715. (arXiv:1211.6113v1 [astro-ph.HE])
The Nearest Millisecond Pulsar Revisited with XMM-Newton: Improved Mass-Radius Constraints for PSR J0437-4715. (arXiv:1211.6113v1 [astro-ph.HE]):
I present an analysis of the deepest X-ray exposure of a radio millisecond
pulsar (MSP) to date, an X-ray Multi Mirror-Newton European Photon Imaging
Camera spectroscopic and timing observation of the nearest known MSP, PSR
J0437--4715. The timing data clearly reveal a secondary broad X-ray pulse
offset from the main pulse by $\sim$0.55 in rotational phase. In the context of
a model of surface thermal emission from the hot polar caps of the neutron
star, this can be plausibly explained by a magnetic dipole field that is
significantly displaced from the stellar center. Such an offset, if commonplace
in MSPs, has important implications for studies of the pulsar population, high
energy pulsed emission, and the pulsar contribution to cosmic ray positrons.
The continuum emission shows evidence for at least three thermal components,
with the hottest radiation most likely originating from the hot magnetic polar
caps and the cooler emission from the bulk of the surface. I present pulse
phase-resolved X-ray spectroscopy of PSR J0437--4715, which for the first time,
properly accounts for the system geometry of a radio pulsar. Such an approach
is essential for unbiased measurements of the temperatures and emission areas
of polar cap radiation from pulsars. Detailed modelling of the thermal pulses,
including relativistic and atmospheric effects, provides a constraint on the
redshift-corrected neutron star radius of R>11.1 km (at 3 sigma conf.) for the
current radio timing mass measurement of 1.76 M_sun. This limit favors "stiff'"
equations of state.
I present an analysis of the deepest X-ray exposure of a radio millisecond
pulsar (MSP) to date, an X-ray Multi Mirror-Newton European Photon Imaging
Camera spectroscopic and timing observation of the nearest known MSP, PSR
J0437--4715. The timing data clearly reveal a secondary broad X-ray pulse
offset from the main pulse by $\sim$0.55 in rotational phase. In the context of
a model of surface thermal emission from the hot polar caps of the neutron
star, this can be plausibly explained by a magnetic dipole field that is
significantly displaced from the stellar center. Such an offset, if commonplace
in MSPs, has important implications for studies of the pulsar population, high
energy pulsed emission, and the pulsar contribution to cosmic ray positrons.
The continuum emission shows evidence for at least three thermal components,
with the hottest radiation most likely originating from the hot magnetic polar
caps and the cooler emission from the bulk of the surface. I present pulse
phase-resolved X-ray spectroscopy of PSR J0437--4715, which for the first time,
properly accounts for the system geometry of a radio pulsar. Such an approach
is essential for unbiased measurements of the temperatures and emission areas
of polar cap radiation from pulsars. Detailed modelling of the thermal pulses,
including relativistic and atmospheric effects, provides a constraint on the
redshift-corrected neutron star radius of R>11.1 km (at 3 sigma conf.) for the
current radio timing mass measurement of 1.76 M_sun. This limit favors "stiff'"
equations of state.
Effects of Kerr Strong Gravity on Quasar X-ray Microlensing. (arXiv:1211.6487v1 [astro-ph.HE])
Effects of Kerr Strong Gravity on Quasar X-ray Microlensing. (arXiv:1211.6487v1 [astro-ph.HE]):
Recent quasar microlensing observations have constrained the sizes of X-ray
emission regions to be within about 10 gravitational radii of the central
supermassive black hole. Therefore, the X-ray emission from lensed quasars is
first strongly lensed by the black hole before it is lensed by the foreground
galaxy and star fields. We present a scheme that combines the initial strong
lensing of a Kerr black hole with standard linearized microlensing by
intervening stars. We find that X-ray microlensed light curves incorporating
Kerr strong gravity can differ significantly from standard curves. The
amplitude of the fluctuations in the light curves can increase or decrease by
~0.65-0.75 mag by including Kerr strong gravity. Larger inclination angles give
larger amplitude fluctuations in the microlensing light curves. Consequently,
current X-ray microlensing observations might have under or overestimated the
sizes of the X-ray emission regions. We estimate this bias using a simple
metric based on the amplitude of magnitude fluctuations. The half light radius
of the X-ray emission region can be underestimated up to ~50% or overestimated
up to ~20%. Underestimates are found in most situations we have investigated.
The only exception is for a disk with large spin, radially flat emission
profile, and observed nearly face on, where an overestimate is found. Thus,
more accurate microlensing size constraints should be obtainable by including
Kerr lensing. The caustic crossing time can differ by months after including
Kerr strong gravity. A simultaneous monitoring of gravitational lensed quasars
in both X-ray and optical bands with densely sampled X-ray light curves might
reveal this feature. We conclude that it should be possible to constrain
important parameters such as inclination angles and black hole spins from
combined Kerr and microlensing effects.
Recent quasar microlensing observations have constrained the sizes of X-ray
emission regions to be within about 10 gravitational radii of the central
supermassive black hole. Therefore, the X-ray emission from lensed quasars is
first strongly lensed by the black hole before it is lensed by the foreground
galaxy and star fields. We present a scheme that combines the initial strong
lensing of a Kerr black hole with standard linearized microlensing by
intervening stars. We find that X-ray microlensed light curves incorporating
Kerr strong gravity can differ significantly from standard curves. The
amplitude of the fluctuations in the light curves can increase or decrease by
~0.65-0.75 mag by including Kerr strong gravity. Larger inclination angles give
larger amplitude fluctuations in the microlensing light curves. Consequently,
current X-ray microlensing observations might have under or overestimated the
sizes of the X-ray emission regions. We estimate this bias using a simple
metric based on the amplitude of magnitude fluctuations. The half light radius
of the X-ray emission region can be underestimated up to ~50% or overestimated
up to ~20%. Underestimates are found in most situations we have investigated.
The only exception is for a disk with large spin, radially flat emission
profile, and observed nearly face on, where an overestimate is found. Thus,
more accurate microlensing size constraints should be obtainable by including
Kerr lensing. The caustic crossing time can differ by months after including
Kerr strong gravity. A simultaneous monitoring of gravitational lensed quasars
in both X-ray and optical bands with densely sampled X-ray light curves might
reveal this feature. We conclude that it should be possible to constrain
important parameters such as inclination angles and black hole spins from
combined Kerr and microlensing effects.
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