10 research outputs found
Ultra Luminous X-ray sources - new distance indicators?
In this paper we fit the NuSTAR and XMM-Newton data of three sources:
NGC7793~P13, NGC5907~ULX1, and Circinus~ULX5. Our single model contains
emission form non-spherical system: neutron star plus accretion disk directed
towards observer. We obtained the very good fit with the reduced per
degree of freedom equal 1.08 for P13, 1.01 for ULX1, and 1.14 for ULX5.The
normalization of our model constrains the distance to the source. The resulting
distances are , and
~Mpc for P13, ULX1 and ULX5 respectively. The distances
to P13 and ULX5 are in perfect agreement with previous distance measurements to
their host galaxies. Our results confirm that P13, ULX1 and ULX5 may contain
central hot neutron star. When the outgoing emission is computed by integration
over the emitting surface and successfully fitted to the data, then the
resulting model normalization is the direct distance indicator.Comment: 5 pages, 3 figures, accepted for publication in A&A Letter
On the Intermediate Line Region in AGNs
In this paper we explore the intermediate line region (ILR) by using the
photoionisation simulations of the gas clouds present at different radial
distances from the center, corresponding to the locations from BLR out to NLR
in four types of AGNs. We let for the presence of dust whenever conditions
allow for dust existence. All spectral shapes are taken from the recent
multi-wavelength campaigns. The cloud density decreases with distance as a
power law. We found that the slope of the power law density profile does not
affect the line emissivity radial profiles of major emission lines: H,
He~II, Mg~II, C~III] ~and [O~III]. When the density of the cloud at the
sublimation radius is as high as 10 cm, the ILR should clearly
be seen in the observations independently of the shape of the illuminating
radiation. Moreover, our result is valid for low ionization nuclear emission
regions of active galaxies.Comment: 8 pages, 2 figures, Accepted for publication in the Journal Frontiers
in Astronomy and Space Science
Variable mass accretion and failed wind explain changing look phenomena in NGC 1365
Changing look active galactic nuclei (CLAGNs) show complex nature in their
X-ray spectral shape and line of sight column density variation. The physical
mechanisms responsible for these variations are unclear. Here, we study the
spectral properties of a CLAGN, NGC\,1365 using combined {\it XMM-Newton} and
{\it NuSTAR} observations to understand the CL behavior. The model fitted mass
accretion rate varied between and and the dynamic corona changed from to . We found
that the variable absorption column density correlates with the mass accretion
rate and the geometry of the corona. The derived wind velocity was sufficiently
low compared to the escape velocity to drive the wind away from the disc for
the epochs when column densities were high. This suggests that the high and
variable absorption can be due to failed winds from the disc. Our estimated
ratio of mass outflow to inflow rate from the inner region of the disc lies
between and . From spectral fitting of the
combined data, we found the mass of the central black hole to be constant
, consistent with earlier
findings. The confidence contours of with other model parameters show
that the model fitted parameters are robust and non-degenerate. Our study
construed that the changing accretion rate, which is a fundamental physical
quantity and the geometry of the corona driving the CL phenomena in NGC\,1365.
The physical picture considered in this work connects both variable continuum
and variable absorbing medium scenarios.Comment: 8 pages, 7 figures, 1 table, accepted for publication in A&A,
comments welcom
The dust origin of the Broad Line Region and the model consequences for AGN unification scheme
We propose a very simple physical mechanism responsible for the formation of
the Low Ionization Line part of the Broad Line Region in Active Galactic
Nuclei. It explains the scaling of the Broad Line Region size with the
monochromatic luminosity, including the exact slope and the proportionality
constant, seen in the reverberation studies of nearby sources. The scaling is
independent from the mass and accretion rate of an active nucleus. The
mechanism predicts the formation of a dust-driven wind in the disk region where
the local effective temperature of a non-illuminated accretion disk drops below
1000 K and allows for dust formation. We explore now the predictive power of
the model with the aim to differentiate between this model and the previously
proposed mechanisms of the formation of the Broad Line Region. We discuss the
expected departures from the universal scaling at long wavelength, and the role
of the inclination angle of the accretion disk in the source. We compare the
expected line profiles with Mg II line profiles in the quasars observed by us
with the SALT telescope. We also discuss the tests based on the presence or
absence of the broad emission lines in low luminosity active galaxies. Finally,
we discuss the future tests of the model to be done with expected ground-based
observations and satellite missions.Comment: Based the talk presented during the COSPAR 2014 meeting, Advances in
Space Research (in press
Constraining X-ray variability of the blazar 3C 273 using XMM-Newton observations over two decades
Blazars exhibit relentless variability across diverse spatial and temporal
frequencies. The study of long- and short-term variability properties observed
in the X-ray band provides insights into the inner workings of the central
engine. In this work, we present timing and spectral analyses of the blazar 3C
273 using the X-ray observations from the telescope
covering the period from 2000 to 2020. The methods of timing analyses include
estimation of fractional variability, long- and short-term flux distribution,
rms-flux relation, and power spectral density analysis. The spectral analysis
include estimating a model independent flux hardness ratio and fitting the
observations with multiplicative and additive spectral models such as
\textit{power-law}, \textit{log-parabola}, \textit{broken power-law}, and
\textit{black body}. The \textit{black body} represents the thermal emission
from the accretion disk, while the other models represent the possible energy
distributions of the particles emitting synchrotron radiation in the jet.
During the past two decades, the source flux changed by of a factor of three,
with a considerable fractional variability of 27\%. However, the intraday
variation was found to be moderate. Flux distributions of the individual
observations were consistent with a normal or log-normal distribution, while
the overall flux distribution including entire observations appear to be rather
multi-modal and of a complex shape. The spectral analyses indicate that
\textit{log-parabola} added with a \textit{black body} gives the best fit for
most of the observations. The results indicate a complex scenario in which the
variability can be attributed to the intricate interaction between the
disk/corona system and the jet.Comment: 18 pages, 8 figures, ApJ accepte
Dusty plasma in active galactic nuclei
Since many years we know that dust in the form of the dusty-molecular torus
is responsible for the obscuration in active galactic nuclei (AGN) at large
viewing angles and thus for the classification of AGN. Recently, we gained some
observational and theoretical insight into geometry of the region and the role
of the dust in the dynamics of the outflow and failed winds. We will briefly
touch on all these aspects, including our dust-based model (FRADO - Failed
Radiatively Accelerated Dusty Outflow) of the formation of the Balmer lines in
AGN.Comment: Partially based on talk at 31st Symposium on the Physics of Ionized
Gases in Belgrade, submitted to the European Physical Journal D Topical
Issue: "Physics of Ionized Gases and Spectroscopy of Isolated Complex
Systems: Fundamentals and Applications
Constraining X-Ray Variability of the Blazar 3C 273 Using XMM-Newton Observations over Two Decades
Blazars exhibit relentless variability across diverse spatial and temporal frequencies. The study of long- and short-term variability properties observed in the X-ray band provides insights into the inner workings of the central engine. In this work, we present timing and spectral analyses of the blazar 3C 273 using the X-ray observations from the XMM-Newton telescope covering the period from 2000 to 2020. The methods of timing analyses include estimation of fractional variability, long- and short-term flux distribution, rms–flux relation, and power spectral density analysis. The spectral analysis include estimating a model-independent flux hardness ratio and fitting the observations with multiplicative and additive spectral models such as power law , log-parabola , broken power law , and blackbody . The blackbody represents the thermal emission from the accretion disk, while the other models represent the possible energy distributions of the particles emitting synchrotron radiation in the jet. During the past two decades, the source flux changed by a factor of three, with a considerable fractional variability of 27%. However, the intraday variation was found to be moderate. Flux distributions of the individual observations were consistent with a normal or log-normal distribution, while the overall flux distribution including all observations appears to be rather multimodal and of a complex shape. The spectral analyses indicate that a log-parabola added to a blackbody gives the best fit for most of the observations. The results indicate a complex scenario in which the variability can be attributed to the intricate interaction between the disk/corona system and the jet