647 research outputs found
An outburst scenario for the X-ray spectral variability in 3C 111
We present a combined Suzaku and Swift BAT broad-band E=0.6-200keV spectral
analysis of three 3C 111 observations obtained in 2010. The data are well
described with an absorbed power-law continuum and a weak (R~0.2) cold
reflection component from distant material. We constrain the continuum cutoff
at E_c~150-200keV, which is in accordance with X-ray Comptonization corona
models and supports claims that the jet emission is only dominant at much
higher energies. Fe XXVI Ly\alpha emission and absorption lines are also
present in the first and second observations, respectively. The modelling and
interpretation of the emission line is complex and we explore three
possibilities. If originating from ionized disc reflection, this should be
emitted at r_in> 50r_g or, in the lamp-post configuration, the illuminating
source should be at a height of h> 30r_g over the black hole. Alternatively,
the line could be modeled with a hot collisionally ionized plasma with
temperature kT = 22.0^{+6.1}_{-3.2} keV or a photo-ionized plasma with
log\xi=4.52^{+0.10}_{-0.16} erg s^{-1} cm and column density N_H > 3x10^23
cm^{-2}. However, the first and second scenarios are less favored on
statistical and physical grounds, respectively. The blue-shifted absorption
line in the second observation can be modelled as an ultra-fast outflow (UFO)
with ionization parameter log\xi=4.47^{+0.76}_{-0.04} erg s^{-1} cm, column
density N_H=(5.3^{+1.8}_{-1.3})x 10^{22} cm^{-2} and outflow velocity v_out =
0.104+/-0.006 c. Interestingly, the parameters of the photo-ionized emission
model remarkably match those of the absorbing UFO. We suggest an outburst
scenario in which an accretion disc wind, initially lying out of the line of
sight and observed in emission, then crosses our view to the source and it is
observed in absorption as a mildly-relativistic UFO.Comment: Accepted for publication in MNARS on July 1st 201
Properties of AGN coronae in the NuSTAR era
The focussing optics of NuSTAR have enabled high signal-to-noise spectra to
be obtained from many X-ray bright Active Galactic Nuclei (AGN) and Galactic
Black Hole Binaries (BHB). Spectral modelling then allows robust
characterization of the spectral index and upper energy cutoff of the coronal
power-law continuum, after accounting for reflection and absorption effects.
Spectral-timing studies, such as reverberation and broad iron line fitting, of
these sources yield coronal sizes, often showing them to be small and in the
range of 3 to 10 gravitational radii in size. Our results indicate that coronae
are hot and radiatively compact, lying close to the boundary of the region in
the compactness - temperature diagram which is forbidden due to runaway pair
production. The coincidence suggests that pair production and annihilation are
essential ingredients in the coronae of AGN and BHB and that they control the
shape of the observed spectra.Comment: 11 pages, 8 figures, accepted for publication in MNRA
Radio continuum and X-ray emission from the most extreme FIR-excess galaxy NGC 1377: An extremely obscured AGN revealed
Galaxies which strongly deviate from the radio-far IR correlation are of
great importance for studies of galaxy evolution as they may be tracing early,
short-lived stages of starbursts and active galactic nuclei (AGNs). The most
extreme FIR-excess galaxy NGC1377 has long been interpreted as a young dusty
starburst, but millimeter observations of CO lines revealed a powerful
collimated molecular outflow which cannot be explained by star formation alone.
We present new radio observations at 1.5 and 10 GHz obtained with the Jansky
Very Large Array (JVLA) and Chandra X-ray observations towards NGC1377. The
observations are compared to synthetic starburst models to constrain the
properties of the central energy source. We obtained the first detection of the
cm radio continuum and X-ray emission in NGC1377. We find that the radio
emission is distributed in two components, one on the nucleus and another
offset by 4.5 to the South-West. We confirm the extreme FIR-excess of the
galaxy, with a 4.2, which deviates by more than
7- from the radio-FIR correlation. Soft X-ray emission is detected on
the off-nucleus component. From the radio emission we estimate for a young
( Myr) starburst a star formation rate SFR0.1 M yr. Such
a SFR is not sufficient to power the observed IR luminosity and to drive the CO
outflow. We find that a young starburst cannot reproduce all the observed
properties of the nucleus of NGC1377. We suggest that the galaxy may be
harboring a radio-quiet, obscured AGN of 10M, accreting at
near-Eddington rates. We speculate that the off-nucleus component may be
tracing an hot-spot in the AGN jet.Comment: 14 pages, accepted for publication on Astronomy and Astrophysics on
08/07/201
Relativistic spectroscopy of the extreme NLS1 IRAS13224-3809
The narrow line Seyfert 1 (NLS1) IRAS 13224-3809 is the most X-ray variable
active galactic nucleus (AGN), exhibiting 0.3-10 keV flux changes of over an
order of magnitude within an hour. We report on the results of the 1.5 Ms 2016
XMM-Newton/NuSTAR observing campaign, which revealed the presence of a 0.24c
ultra-fast outflow in addition to the well-known strong relativistic
reflection. We also summarise other key results of the campaign, such as the
first detection of a non-linear RMS-flux relation in an accreting source,
correlations between outflow absorption strength/velocity and source flux, and
a disconnect between the X-ray and UV emission. Our results are consistent with
a scenario where a disk wind is launched close to the black hole, imprinting
absorption features into the spectrum and variability.Comment: 6 pages, 7 figures, contributed talk at "Revisiting narrow-line
Seyfert 1 galaxies and their place in the Universe" (Padova, April 2018).
Accepted for publication in Proceedings of Science, PoS(NLS1-2018)03
Coronal Properties of Swift/BAT-selected Seyfert 1 AGNs Observed with NuSTAR
The NuSTAR observatory, with its high sensitivity in hard X-rays, has enabled detailed broadband modeling of the X-ray spectra of active galactic nuclei (AGNs), thereby allowing constraints to be placed on the high-energy cutoff of the X-ray coronal continuum. We investigate the spectral properties of a sample of 46 NuSTAR-observed Seyfert 1 AGNs selected from the Swift/Burst Alert Telescope 70 month hard X-ray survey. Our measurements of the high-energy cutoff of the continuum from modeling the NuSTAR X-ray spectra are used to map out the temperature–compactness (θ–l) plane for AGN coronae. We find that most of the coronae lie clustered near the boundary for runaway pair production, suggesting that annihilation and pair production act to regulate the temperature of the corona. We discuss the implications of coronae whose high-energy cutoff may indicate a low coronal temperature on the heating and thermalization mechanisms in the corona
-Scale Decoupling of the Mechanical Relaxation and Diverging Shear Wave Propagation Lengthscale in Triphenylphosphite
We have performed depolarized Impulsive Stimulated Scattering experiments to
observe shear acoustic phonons in supercooled triphenylphosphite (TPP) from
10 - 500 MHz. These measurements, in tandem with previously performed
longitudinal and shear measurements, permit further analyses of the relaxation
dynamics of TPP within the framework of the mode coupling theory (MCT). Our
results provide evidence of coupling between the shear and
longitudinal degrees of freedom up to a decoupling temperature = 231 K. A
lower bound length scale of shear wave propagation in liquids verified the
exponent predicted by theory in the vicinity of the decoupling temperature
Disentangling the Complex Broadband X-ray Spectrum of IRAS 13197-1627 with NuSTAR, XMM-Newton and Suzaku
We present results from a coordinated -+ observation of
the type 1.8 Seyfert galaxy IRAS 13197-1627. This is a highly complex source,
with strong contributions from relativistic reflection from the inner accretion
disk, neutral absorption and further reprocessing by more distant material, and
ionised absorption from an outflow. We undertake a detailed spectral analysis
combining the broadband coverage provided by -+ with a
multi-epoch approach incorporating archival observations performed by
- and . Our focus is on characterising the reflection from
the inner accretion disk, which previous works have suggested may dominate the
AGN emission, and constraining the black hole spin. Using lamppost disk
reflection models, we find that the results for the inner disk are largely
insensitive to assumptions regarding the geometry of the distant reprocessor
and the precise form of the illuminating X-ray continuum. However, these
results do depend on the treatment of the iron abundance of the distant
absorber/reprocessor. The multi-epoch data favour a scenario in which the AGN
is chemically homogeneous, and we find that a rapidly rotating black hole is
preferred, with , but a slowly-rotating black hole is not
strongly excluded. In addition to the results for the inner disk, we also find
that both the neutral and ionised absorbers vary from epoch to epoch, implying
that both have some degree of inhomogeneity in their structure.Comment: 15 pages, 7 figures, accepted for publication in MNRA
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