98 research outputs found
Properties of the propagating oscillatory shock wave in the accretion flows around few transient black hole candidates during their outbursts
In our study of the timing properties of few Galactic black hole candidates
evolutions of the low and intermediate frequency quasi-periodic oscillations
(LIFQPOs) are observed. In 2005, for explaining evolution of QPO frequency
during rising phase of 2005 GRO J1655-40 outburst, Chakrabarti and his students
introduced a new model, namely propagating oscillatory shock (POS) model. Here
we present the results obtained from the same POS model fitted QPO evolutions
during both the rising and declining phases of the outbursts of 2005 GRO
J165540, 2010-11 GX 339-4, and 2010 & 2011 H 1743-322.Comment: 3 pages, 3 figures, Thirteenth Marcel Grossmann (MG13) Conference
Proceedin
A comparative study of the timing and the spectral properties during two recent outbursts (2010 & 2011) of H 1743-322
The Galactic black hole candidate (BHC) H~1743-322 recently exhibited two
outbursts in X-rays in August 2010 & April 2011. The nature (outburst profile,
evolution of quasi-periodic oscillation (QPO) frequency and spectral states,
etc.) of these two successive outbursts, which continued for around two months
each, are very similar. We present the results obtained from a comparative
study on the temporal and the spectral properties of the source during these
two outbursts. The evolutions of QPOs observed in both the outbursts were well
fitted with propagating oscillatory shock (POS) model. During both the
outbursts, the observed spectral states (i.e, hard, hard-intermediate,
soft-intermediate and soft) follow the `standard' type of hysteresis-loop,
which could be explained with two component advective flow (TCAF) model.Comment: 2 pages, 2 figures, Thirteenth Marcel Grossmann (MG13) Conference
Proceedin
Spectral signatures of dissipative standing shocks and mass outflow in presence of Comptonization around a black hole
Accretion flows having positive specific energy are known to produce outflows
and winds which escape to a large distance. According to Two Component
Advective Flow (TCAF) model, centrifugal pressure dominated region of the flow
just outside the black hole horizon, with or without shocks, acts as the base
of this outflow. Electrons from this region are depleted due to the wind and
consequently, energy transfer rate due to inverse Comptonization of low energy
photons are affected. Specifically, it becomes easier to cool this region and
emerging spectrum is softened. Our main goal is to show spectral softening due
to mass outflow in presence of Compton cooling. To achieve this, we modify
Rankine-Hugoniot relationships at the shock front when post-shock region
suffers mass loss due to winds and energy loss due to inverse Comptonization.
We solve two-temperature equations governing an accretion flow around a black
hole which include Coulomb exchange between protons and electrons and other
major radiative processes such as bremsstrahlung and thermal Comptonization. We
then compute emitted spectrum from this post-shock flow. We also show how
location of standing shock which forms outer boundary of centrifugal barrier
changes with cooling. With an increase in disc accretion rate ,
cooling is enhanced and we find that the shock moves in towards the black hole.
With cooling, thermal pressure is reduced, and as a result, outflow rate is
decreased. We thus directly correlate outflow rate with spectral state of the
disc.Comment: 10 pages, 6 figures, Accepted for publication in Astrophysics and
Space Scienc
Properties of X-ray Flux of Jets During 2005 Outburst of Swift J1753.5-0127 Using TCAF Solution
Galactic black hole candidate Swift~J1753.5-0127 was discovered on 2005 June
30 by the Swift Burst Alert Telescope. We study the accretion flow properties
during its very first outburst through careful analysis of the evolution of the
spectral and the temporal properties using the two-component advective flow
(TCAF) paradigm. RXTE proportional counter array spectra in keV are
fitted with the current version of the TCAF model fits file to estimate
physical flow parameters, such as two component (Keplerian disk and
sub-Keplerian halo) accretion rates, properties of the Compton cloud, probable
mass of the source, etc. The source is found to be in harder (hard and
hard-intermediate) spectral states during the entire phase of the outburst with
very significant jet activity. Since in TCAF solution, the model normalization
is constant for any particular source, any requirement of significantly
different normalization to have a better fit on certain days would point to
X-ray contribution from components not taken into account in the current TCAF
model fits file. By subtracting the contribution using actual normalization, we
derive the contribution of X-rays from the jets and outflows. We study its
properties, such as its magnitude and spectra. We find that on some days, up to
about 32\% X-ray flux is emitted from the base of the jet itself.Comment: 11 pages, 4 figures, 1 table (accepted for publication in ApJ
Spectral study of GX 339-4 with TCAF using Swift/XRT and NuSTAR Observation
We fit spectra of galactic transient source GX~339-4 during its 2013 outburst
using Two Component Advective Flow (TCAF) solution. For the first time, we are
fitting combined NuSTAR and Swift observation with TCAF. We use TCAF to fit
0.8-9.0~keV Swift and 4-79 keV NuSTAR spectra along with the LAOR model. To fit
the data we use disk accretion rate, halo accretion rate, size of the Compton
cloud and the density jump of advective flows at this cloud boundary as model
parameters. From TCAF fitted flow parameters, and energy spectral index we
conclude that the source was in the hard state throughout this particular
outburst. The present analysis also gives some idea about the broadening of Fe
with the accretion rate. Since TCAF does not include Fe line yet,
we make use of the `LAOR model' as a phenomenological model and find an
estimate of the Kerr parameter to be for this candidate.Comment: 10 pages, 4 figures, 1 table, Accepted for Publication in
Astrophysics and Space Scienc
Delayed Outburst of H 1743--322 in 2003 and relation with its other outbursts
The Galactic transient black hole candidate H 1743--322 exhibited a long
duration outburst in 2003 after more than two and a half decades of inactivity.
The 2003 event was extensively studied in multi-wavelength bands by many
groups. The striking feature is that the total energy released is extremely
high as compared to that in tens of outbursts which followed. In this paper, we
look at this event and study both the spectral and temporal properties of the
source using two component advective flow (TCAF) paradigm. We extract accretion
flow parameters for each observation from spectral properties of the decay
phase and determine the mass of the black hole. We computed the energy released
during all the known outbursts since 2003 and showed that on an average, the
energy release in an outburst is proportional to the duration of the quiescent
state just prior to it, with the exception of the 2004 outburst. A constant
rate of supply of matter from the companion cannot explain the energy release
in 2004 outburst. However, if the energy release of 2003 is incomplete and the
leftover is released in 2004, then the companion's rate of matter supply can be
constant since 1977 till date. We believe that erratic behaviour of viscosity
at the accumulation radius of matter as well as location the
itself, rather than the random variation of mass transfer rate from the
companion, could be responsible for non-uniformity in outburst pattern. We
discuss several factors on which the waiting time and duration of the next
outburst could depend.Comment: 29 pages, 6 figures, 3 tables (accepted for publication in "Advances
in Space Research"
Inference on accretion flow dynamics using TCAF solution from the analysis of spectral evolution of H 1743-322 during 2010 outburst
We study accretion flow dynamics of Galactic transient black hole candidate
(BHC) H 1743-322 during its 2010 outburst by analyzing spectral data using Two
Component (Keplerian and sub-Keplerian) Advective Flow (TCAF) solution, after
its inclusion in XSPEC as a local model. We compare our TCAF solution fitted
results with combined disk black body and power-law model fitted results and
find a similar smooth variation of thermal (Keplerian or disk black body) and
non-thermal (power-law or sub-Keplerian) fluxes/rates in two types of model
fits. For a spectral analysis, 2.5-25 keV spectral data from RXTE PCA
instrument are used. From the TCAF solution fit, accretion flow parameters,
such as Keplerian rate, sub-Keplerian rate, location of centrifugal pressure
supported shock and strength of the shock are extracted, thus providing a
deeper understanding of accretion process and properties of accretion disks
around BHC H 1743-322 during its X-ray outburst. Based on the halo to disk
accretion rate ratio (ARR), shock properties, accretion rates and nature of
quasi-periodic oscillations (QPOs, if observed) entire outburst is classified
into four different spectral states, such as, hard, hard-intermediate,
soft-intermediate, and soft. From time variation of intrinsic flow parameters
it appears that their evolutions in decline phase do not retrace path of rising
phase. Since our current model does not include magnetic fields, spectral
turnover at energies beyond 500-600 keV cannot be explained.Comment: 7 pages, 4 figures, 1 table; accepted for publication in Ap
Characterization of GX 339-4 outburst of 2010-11: analysis by xspec using two component advective flow model
We study spectral properties of GX 339-4 during its 2010-11 outburst with Two
Component Advective Flow (TCAF) model after its inclusion in XSPEC as a table
model. We compare results fitted by TCAF model with combined disk black body
and power-law model. For a spectral fit, we use 2.5-25 keV spectral data of the
PCA instrument onboard RXTE satellite. From our fit, accretion flow parameters
such as Keplerian (disk) rate, sub-Keplerian (halo) rate, location and strength
of shock are extracted. We quantify how the disk and the halo rates vary during
the entire outburst. We study how the halo to disk accretion rate ratio (ARR),
quasi-periodic oscillations (QPOs), shock locations and its strength vary when
the system passes through hard, hard-intermediate, soft-intermediate, and soft
states. We find pieces of evidence of monotonically increasing and decreasing
nature of QPO frequencies depending on the variation of ARR during rising and
declining phases. Interestingly, on days of transition from hard state to
hard-intermediate spectral state (during the rising phase) or vice-versa
(during decline phase), ARR is observed to be locally maximum. Non-constancy of
ARR while obtaining reasonable fits points to the presence of two independent
components in the flow.Comment: 12 Pages, 4 Figures, 1 Table, and 1 Appendix (Table
Spectral Analysis of Class Data of GRS 1915+105 Using TCAF Solution
The class variable source GRS 1915+105 exhibits a wide range of time
variabilities in time scales of a few seconds to a few days. Depending on the
count rates in different energy bands and the nature of the conventional
color-color diagram, the variabilities were classified into sixteen classes,
which were later sequenced in ascending order of Comptonization Efficiency
(CE). The CE is the ratio of the phenomenological power-law and disk blackbody
model fitted spectral photon fluxes. For a better understanding of the flow
dynamics in one of the variability classes, namely , we fitted spectra
with the physical two-component advective flow (TCAF) model. In class,
X-ray flux is steady with no significant variation, however, various
subclasses are observed at different X-ray flux and variations of count rates
across different subclasses must be linked to the variation of flow
parameters such as the accretion rates, be it the Keplerian disc rate and/or
the low angular momentum halo rate. We find that in the classes,
which are reportedly devoid of significant outflows, the spectra could be
fitted well using TCAF solution alone. In the class, which are
always linked with outflows, a cutoff power-law model is needed in addition to
the TCAF solution. At the same time, the normalization required by this model
along with the variation of photon index and exponential roll-off factor
provides us with the information on the relative dominance of the outflow in
the latter two classes. TCAF fit also provides us with the size and location of
the Compton cloud along with its optical depth. Thus by fitting with TCAF, a
physical understanding of the flow geometry in different classes of GRS
1915+105 has been obtained.Comment: 13 pages, 6 figures, 3 tables, Accepted for publication in Research
in Astronomy and Astrophysics on June 4, 2020 (Original version submitted on
February 20, 2020
Inference on Disk-Jet Connection of MAXI J1836-194: Analysis with the TCAF Solution
Galactic transient black hole candidate (BHC) MAXI~J1836-194 was discovered
on 2011 Aug 30, by MAXI/GSC and Swift/BAT. The source activity during this
outburst was continued for ~3 months before entering into the quiescent state.
It again became active in March 2012 and continued for another ~2 months. In
this paper, 3-25 keV RXTE/PCA spectra of 2011 outburst and 0.5-10.0 keV
Swift/XRT data during its 2012 outburst are analyzed with the two-component
advective flow (TCAF) model based fits file in XSPEC. We calculate the X-ray
contributions coming from jets/outflow using a newly developed method based on
the deviation of the TCAF model normalization. We also studied the correlation
between observed radio and estimated jet X-ray fluxes. The correlation indices
() are found to be , and , when the 7.45 GHz VLA radio flux is
correlated with the total X-ray and the jet X-ray fluxes in 3-25 keV range
respectively. It has been found that the jet contributes in X-rays up to a
maximum of 86\% during its 2011 outburst. This makes the BHC MAXI J1836-194 to
be strongly jet dominated during the initial rising phase.Comment: 12 pages, 5 figures, 2 tables, submitted to Astrophysics and Space
Scienc
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