16,654 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
The third conformer of graphane: A first principles DFT based study
We propose, on the basis of our first principles density functional based
calculations, a new isomer of graphane, in which the C-H bonds of a hexagon
alternate in 3-up, 3-down fashion on either side of the sheet. This 2D puckered
structure called 'stirrup' has got a comparable stability with the previously
discovered chair and boat conformers of graphane. The physico-chemical
properties of this third conformer are found to be similar to the other two
conformers of graphane with an insulating direct band gap of 3.1 eV at the
{\Gamma} point. Any other alternative hydrogenation of the graphene sheet
disrupts its symmetric puckered geometry and turns out to be energetically less
favorable.Comment: 15 pages, 4 figure
Thermodynamics of Morpholine Complexes of Co(II), Cu(II) & Zn(II) Fluoborates-A Study in Solid Phase
135-13
Sharp change over from compound nuclear fission to shape dependent quasi fission
Fission fragment mass distribution has been measured from the decay of
Bk nucleus populating via two entrance channels with slight difference
in mass asymmetries but belonging on either side of the Businaro Gallone mass
asymmetry parameter. Both the target nuclei were deformed. Near the Coulomb
barrier, at similar excitation energies the width of the fission fragment mass
distribution was found to be drastically different for the N +
Th reaction compared to the B + U reaction. The entrance
channel mass asymmetry was found to affect the fusion process sharply.Comment: 4 pages,6 figure
Giant Dipole Resonance Width in near-Sn Nuclei at Low Temperature and High Angular Momentum
High energy gamma-rays in coincidence with low energy yrast gamma-rays have
been measured from 113Sb, at excitation energies of 109 and 122 MeV, formed by
bombarding 20Ne on 93Nb at projectile energies of 145 and 160 MeV respectively
to study the role of angular momentum (J) and temperature (T) over Giant Dipole
Resonance (GDR) width. The maximum populated angular momenta for fusion were
67hbar and 73hbar respectively for the above-mentioned beam energies. The high
energy photons were detected using a Large Area Modular BaF2 Detector Array
(LAMBDA) along with a 24-element multiplicity filter. After pre-equilibrium
corrections, the excitation energy E* was averaged over the decay steps of the
compound nucleus (CN). The average values of temperature, angular momentum, CN
mass etc. have been calculated by the statistical model code CASCADE. Using
those average values, results show the systematic increase of GDR width with T
which is consistent with Kusnezov parametrization and the Thermal Shape
Fluctuation Model. The rise of GDR width with temperature also supports the
assumptions of adiabatic coupling in the Thermal Shape Fluctuation Model. But
the GDR widths and corresponding reduced plots with J are not consistent with
the theoretical model at high spins.Comment: 19 pages, 10 figures, Submitted to Physics Review
See-saw fermion masses in an SO(10) GUT
In this work we study an SO(10) GUT model with minimum Higgs representations
belonging only to the 210 and 16 dimensional representations of SO(10). We add
a singlet fermion S in addition to the usual 16 dimensional representation
containing quarks and leptons. There are no Higgs bi-doublets and so charged
fermion masses come from one-loop corrections. Consequently all the fermion
masses, Dirac and Majorana, are of the see-saw type. We minimize the Higgs
potential and show how the left-right symmetry is broken in our model where it
is assumed that a D-parity odd Higgs field gets a vacuum expectation value at
the grand unification scale. From the renormalization group equations we infer
that in our model unification happens at 10^{15} GeV and left-right symmetry
can be extended up to some values just above 10^{11} GeV. The Yukawa sector of
our model is completely different from most of the standard grand unified
theories and we explicitly show how the Yukawa sector will look like in the
different phases and briefly comment on the running of the top quark mass. We
end with a brief analysis of lepton number asymmetry generated from the
interactions in our model.Comment: 30 pages, 10 figure
Order a improved renormalization constants
We present non-perturbative results for the constants needed for on-shell
improvement of bilinear operators composed of Wilson fermions. We work
at and 6.2 in the quenched approximation. The calculation is done
by imposing axial and vector Ward identities on correlators similar to those
used in standard hadron mass calculations. A crucial feature of the calculation
is the use of non-degenerate quarks. We also obtain results for the constants
needed for off-shell improvement of bilinears, and for the scale and
scheme independent renormalization constants, (Z_A), (Z_V) and (Z_S/Z_P).
Several of the constants are determined using a variety of different Ward
identities, and we compare their relative efficacies. In this way, we find a
method for calculating that gives smaller errors than that used
previously. Wherever possible, we compare our results with those of the ALPHA
collaboration (who use the Schr\"odinger functional) and with 1-loop
tadpole-improved perturbation theory.Comment: 48 pages. Modified "axis" source for figures also included. Typos
corrected (version published in Phys. Rev. D
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