266 research outputs found
Variations in the Cyclotron Resonant Scattering Features during 2011 outburst of 4U 0115+63
We study the variations in the Cyclotron Resonant Scattering Feature (CRSF)
during 2011 outburst of the high mass X-ray binary 4U 0115+63 using
observations performed with Suzaku, RXTE, Swift and INTEGRAL satellites. The
wide-band spectral data with low energy coverage allowed us to characterize the
broadband continuum and detect the CRSFs. We find that the broadband continuum
is adequately described by a combination of a low temperature (kT ~ 0.8 keV)
blackbody and a power-law with high energy cutoff (Ecut ~ 5.4 keV) without the
need for a broad Gaussian at ~ 10 keV as used in some earlier studies. Though
winds from the companion can affect the emission from the neutron star at low
energies (< 3 keV), the blackbody component shows a significant presence in our
continuum model. We report evidence for the possible presence of two
independent sets of CRSFs with fundamentals at ~ 11 keV and ~ 15 keV. These two
sets of CRSFs could arise from spatially distinct emitting regions. We also
find evidence for variations in the line equivalent widths, with the 11 keV
CRSF weakening and the 15 keV line strengthening with decreasing luminosity.
Finally, we propose that the reason for the earlier observed anti-correlation
of line energy with luminosity could be due to modelling of these two
independent line sets (~ 11 keV and ~ 15 keV) as a single CRSF.Comment: 12 pages, 8 figures (4 in colour), 6 tables. Accepted for publication
in MNRAS. Typos corrected, Figure 8 changed and some changes to draf
STUDY AND MECHANICAL TESTING OF FIBER REINFORCED PLASTIC LAMINATE AND CARBON FIBER LAMINATE COMPOSITE
The use of composite materials at industrial and domestic levels is increasing day by day, due to which the work in the direction of enhancing its mechanical property is being on a fast pace. In this study, the mechanical properties of Polyester resin and Carbon Fibre Composite were analyzed experimentally. Tensile and Compressive strength of the specimen were determined and compared. It was found both laminates together provides a positive impact in the enhancement of mechanical properties of the composite
Survey on Optimization Methods For Spectrum Sensing in Cognitive Radio Network
A cognitive radio is a capable Technology, which has provided a great innovation in wireless communication system as to improve the efficiency of the electromagnetic spectrum utilization in wireless network. The technology allows unlicensed user or secondary user to use the vacant spectrum of licensed user through dynamic channel assignment strategies to improve the spectral utilization and hence cognitive radio avoids spectrum shortage. Cooperative sensing is one of the fastest growing areas of research and it is likely to be a key enabling technology, for efficiently spectrum sensing in future. For this several spectrum sensing are available, which can detect the white spaces or spectrum holes and share them to the secondary user without interfering with the movement of licensed user. In order to reliably and swiftly detect spectrum holes in cognitive radios, optimization must be used. In this paper we study different optimization for spectrum searching and sharing and also compare this optimization on the basis of probability of total error on fading channel
Variations in the cyclotron resonant scattering features during 2011 outburst of 4U 0115+63
We study the variations in the Cyclotron Resonant Scattering Feature (CRSF) during 2011
outburst of the high mass X-ray binary 4U 0115+63 using observations performed with
Suzaku, RXTE, Swift and INTEGRAL satellites. The wide-band spectral data with low-energy
coverage allowed us to characterize the broad-band continuum and detect the CRSFs. We find
that the broad-band continuum is adequately described by a combination of a low temperature
(kT ∼ 0.8 keV) blackbody and a power law with high energy cutoff (Ecut ∼ 5.4 keV) without
the need for a broad Gaussian at ∼10 keV as used in some earlier studies. Though winds
from the companion can affect the emission from the neutron star at low energies (<3 keV),
the blackbody component shows a significant presence in our continuum model. We report
evidence for the possible presence of two independent sets of CRSFs with fundamentals at ∼11
and ∼15 keV. These two sets of CRSFs could arise from spatially distinct emitting regions.
We also find evidence for variations in the line equivalent widths, with the 11 keV CRSF
weakening and the 15 keV line strengthening with decreasing luminosity. Finally, we propose
that the reason for the earlier observed anticorrelation of line energy with luminosity could be
due to modelling of these two independent line sets (∼11 and ∼15 keV) as a single CRSF
XMM observations of the narrow-line QSO PHL 1092: Detection of a high and variable soft component
We present results based on an XMM-Newton observation of the high luminosity
narrow-line QSO PHL 1092 performed in 2003 January. The 0.3 - 10 keV spectrum
is well described by a model which includes a power-law (Gamma ~ 2.1) and two
blackbody components (kT ~ 130 eV and kT ~ 50 eV). The soft X-ray excess
emission is featureless and contributes ~ 80% to the total X-ray emission in
the 0.3 - 10 keV band. The most remarkable feature of the present observation
is the detection of X-ray variability at very short time scale: the X-ray
emission varied by 35% in about 5000 s. We find that this variability can be
explained by assuming that only the overall normalization varied during the
observation. There was no evidence for any short term spectral variability and
the spectral shape was similar even during the ASCA observation carried out in
1997. Considering the high intrinsic luminosity (~ 2x10^45 erg/s) and the large
inferred mass of the putative black hole (~ 1.6x10^8 M_sun), the observed time
scale of variability indicates emission at close to Eddington luminosity
arising from very close to the black hole. We suggest that PHL 1092 in
particular (and narrow line Seyfert galaxies in general) is a fast rotating
black hole emitting close to its Eddington luminosity and the X-ray emission
corresponds to the high-soft state seen in Galactic black hole sources.Comment: 7 figures, 8 pages, emulateapj style, ApJ in pres
A high-density relativistic reflection origin for the soft and hard X-ray excess emission from Mrk 1044
We present the first results from a detailed spectral-timing analysis of a
long (130 ks) XMM-Newton observation and quasi-simultaneous NuSTAR and
Swift observations of the highly-accreting narrow-line Seyfert 1 galaxy Mrk
1044. The broadband (0.350 keV) spectrum reveals the presence of a strong
soft X-ray excess emission below 1.5 keV, iron K emission
complex at 67 keV and a `Compton hump' at 1530 keV. We find
that the relativistic reflection from a high-density accretion disc with a
broken power-law emissivity profile can simultaneously explain the soft X-ray
excess, highly ionized broad iron line and the Compton hump. At low frequencies
( Hz), the power-law continuum dominated 1.55 keV band
lags behind the reflection dominated 0.31 keV band, which is explained with
a combination of propagation fluctuation and Comptonization processes, while at
higher frequencies ( Hz), we detect a soft lag which is
interpreted as a signature of X-ray reverberation from the accretion disc. The
fractional root-mean-squared (rms) variability of the source decreases with
energy and is well described by two variable components: a less variable
relativistic disc reflection and a more variable direct coronal emission. Our
combined spectral-timing analyses suggest that the observed broadband X-ray
variability of Mrk~1044 is mainly driven by variations in the location or
geometry of the optically thin, hot corona.Comment: 23 pages, 19 figures, 4 tables, Published in MNRA
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