92 research outputs found
MAXI J0637-430: A Possible Candidate for Bulk Motion Comptonization?
The transient Galactic black hole candidate MAXI J0637-430 went through an
outburst in 2019--20 for the very first time. This outburst was active for
almost 6 months from November 2019 to May 2020. We study the spectral
properties of this source during that outburst using archival data from NICER,
Swift, and NuSTAR satellites/instruments. We have analyzed the source during 6
epochs on which simultaneous NICER--NuSTAR and Swift/XRT--NuSTAR data were
available. Using both phenomenological and physical model fitting approaches,
we analyzed the spectral data in the broad keV energy band. We first
used a combination of disk blackbody with power-law, disk blackbody with broken
power-law, and disk blackbody with power-law and bmc models. For a better
understanding of the accretion picture, e.g., understanding how the accretion
rates change with the changing size of the perceived Compton cloud, we used the
two-component advective flow (TCAF) model with broken power-law, TCAF with
power-law and bmc models. For last 3 epochs, the diskbb+power-law and TCAF
models were able to spectrally fit the data for acceptable .
However, for the first 3 epochs, we needed an additional component to fit
spectra for acceptable . From our analysis, we reported about the
possible presence of another component during these first 3 epochs when the
source was in the high soft state. This additional component in this state is
best described by the bulk motion Comptonization phenomenon. From the TCAF
model fitting, we estimated the average mass of the source as
.Comment: 16 pages, 5 figure
Accretion Flow Properties of EXO 1846-031 During its Multi-Peaked Outburst After Long Quiescence
We study the recent outburst of the black hole candidate EXO 1846-031 which
went into an outburst in 2019 after almost 34 years in quiescence. We use
archival data from Swift/XRT, MAXI/GSC, NICER/XTI and NuSTAR/FPM
satellites/instruments to study the evolution of the spectral and temporal
properties of the source during the outburst. Low energy X-ray flux of the
outburst shows multiple peaks making it a multipeak outburst. Evolving type-C
quasi-periodic oscillations (QPOs) are observed in the NICER data in the hard,
hard intermediate and soft intermediate states. We use the physical Two
Component Advective Flow (TCAF) model to analyze the combined spectra of
multiple satellite instruments. According to the TCAF model, the accreting
matter is divided into Keplerian and sub-Keplerian parts, and the variation in
the observed spectra in different spectral states arises out of the variable
contributions of these two types of accreting matter in the total accretion
rate. Studying the evolution of the accretion rates and other properties of the
accretion flow obtained from the spectral analysis, we show how the multiple
peaks in the outburst flux arises out of discontinuous supply and different
radial velocities of two types of accreting matter from the pile-up radius. We
detect an Fe emission line at keV in the hard and the intermediate
states in the NICER spectra. We determine the probable mass of the black hole
to be from the spectral analysis with the TCAF
model. We also estimate viscous time scale of the source in this outburst to be
days from the peak difference of the Keplerian and sub-Keplerian mass
accretion rates.Comment: 15 pages, 8 Figures, 2 Tables (In Communication ApJ
Synthetic strategy of porous ZnO and CdS nanostructures doped ferroelectric liquid crystal and its optical behavior
A simple and scalable chemical approach has been proposed for the generation of 1-dimensional nanostructures of two most important inorganic materials such as zinc oxide and cadmium sulfide. By controlling the growth habit of the nanostructures with manipulated reaction conditions, the diameter and uniformity of the nanowires/nanorods were tailored. We studied extensively optical behavior and structural growth of CdS NWs and ZnO NRs doped ferroelectric liquid crystal Felix-017/100. Due to doping band gap has been changed and several blue shifts occurred in photoluminescence spectra because of nanoconfinement effect and mobility of charges
Effect of acyl chloride functionalized carbon black on mechanical and thermal properties of acrylonitrile butadiene styrene/polyaniline blend
472-479Pristine Carbon Black (CB) has been first oxidised to introduce carboxylic acid functional group on the surface of CB, followed by treating with thionyl chloride. The presence of acyl chloride group in the resultant product has been ascertained by FTIR spectroscopy. The acyl chloride functionalized CB (CB-Ac) has been used as a filler in Acrylonitrile Butadiene Styrene (ABS)/Polyaniline (PANI) blend to improve the mechanical and thermal properties. Further addition of Nanoclay (NC) in the blend has improved the dispersion of fillers in the polymer matrix as confirmed by FESEM images and XRD pattern. The Ultimate Tensile Analysis (UTA) and Dynamic mechanical analysis (DMA) have been studied. The Young modulus has shown increment of 48% and 66% in case of CB-Ac and CB-Ac/NC filled blend, respectively. The ultimate tensile strength has also been found to be increased in CB-Ac and CB-Ac/NC filled blends. DMA has given the insight about the excellent improvement in damping properties of the composites due to filler addition. Themo gravimetric analysis (TGA) and Differential scanning calorimetry (DSC) has been carried out to ascertain the thermal properties. TGA has revealed the excellent augmentation in the flame retardancy and heat resistance of the composites due to CB-Ac/NC loading. DSC study has further verified the improvement in degree of crystallinity due to interfacial attraction between fillers and polymer matrix
Switching of ferroelectric liquid crystal doped with cetyltrimethylammonium bromide-assisted CdS nanostructures
Large scale high yield cadmium sulfide (CdS) nanowires with uniform diameter were synthesized using a rapid and simple solvo-chemical and hydrothermal route assisted by the surfactant cetyltrimethylammonium bromide (CTAB). Unique CdS nanowires of different morphologies could be selectively produced by only varying the concentration of CTAB in the reaction system with cadmium acetate, sulfur powder and ethylenediamine. We obtained CdS nanowires with diameters of 64–65 nm and lengths of up to several micrometers. A comparative study of the optical properties of ferroelectric liquid crystal (FLC) Felix-017/100 doped with 1% of CdS nanowires was performed. Response times of the order of from 160 to 180 μs, rotational viscosities of the order of from 5000 to 3000 mN s m−2 and polarizations of the order of from 10 to 70 nC cm−2 were measured. We also observed an anti-ferroelectric to ferroelectric transition for CdS doped FLC instead of the ferroelectric to paraelectric transition for pure FLC
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