116,949 research outputs found
Using XMM-Newton to study the energy dependent variability of H 1743-322 during its 2014 outburst
Black hole transients during bright outbursts show distinct changes of their
spectral and variability properties as they evolve during an outburst, that are
interpreted as evidence for changes in the accretion flow and X-ray emitting
regions. We obtained an anticipated XMM-Newton ToO observation of H 1743-322
during its outburst in September 2014. Based on data of eight outbursts
observed in the last 10 years we expected to catch the start of the
hard-to-soft state transition. The fact that neither the general shape of the
observed power density spectrum nor the characteristic frequency show an energy
dependence implies that the source still stays in the low-hard state at the
time of our observation near outburst peak. The spectral properties agree with
the source being in the low-hard state and a Swift/XRT monitoring of the
outburst reveals that H 1743-322 stays in the low-hard state during the entire
outburst (a. k. a. 'failed outburst'). We derive the averaged QPO waveform and
obtain phase-resolved spectra. Comparing the phase-resolved spectra to the
phase averaged energy spectrum reveals spectral pivoting. We compare
variability on long and short time scales using covariance spectra and find
that the covariance ratio does not show an increase towards lower energies as
has been found in other black hole X-ray binaries. There are two possible
explanations: either the absence of additional disc variability on longer time
scales is related to the rather high inclination of H 1743-322 compared to
other black hole X-ray binaries or it is the reason why we observe H 1743-322
during a failed outburst. More data on failed outbursts and on high-inclination
sources will be needed to investigate these two possibilities further.Comment: 9 pages, 7 figures, accepted by MNRA
Detection of distinct power spectra in soft and hard X-ray bands in the hard state of GRS 1915+105
The well-known black hole X-ray binary GRS 1915+105 is a unique source in the
sense that it cannot be classified within the standard picture of black hole
binary states. In this work we study archival XMM-Newton observations taken
between 2003 and 2004 of the \c{hi} variability class of GRS 1915+105, which
corresponds to the hard state in the standard black hole X-ray binary state
classification. The crucial point of our study is that by using XMM-Newton data
we can access the variability below 3 keV, an energy range that is not covered
with RXTE. We focus on the study of the power spectral shape in the soft and
hard X-ray band, in light of our work done with Swift on MAXI J1659-152. In the
hard band (above 2.5 keV) power density spectra consist of band-limited noise
and quasi-periodic oscillations, corresponding to the power spectral shape seen
in the hard or intermediate state, while in the soft band the averaged power
density spectrum is consistent with a power-law noise, corresponding to the
power spectral shape usually seen in the soft state. The coexisting of two
different power spectral shapes in the soft and hard band, where the soft band
power spectrum is dominated by a power-law noise, is consistent with MAXI
J1659-152, and confirms the energy dependence of power spectral states. Our
additional spectral analysis shows that the disc component does contribute to
the soft band flux. These findings support that the observed black hole power
spectral state depends on which spectral component we are looking at, which
implies that power spectral analysis is probably a more sensitive method than
spectral modeling to trace the emergence of the disc component in the hard or
intermediate state.Comment: 9 pages, 5 figures, submitted to MNRA
Comment on "Spectroscopic Evidence for Multiple Order Parameter Components in the Heavy Fermion Superconductor CeCoIn"
Recently, Rourke et al. reported point-contact spectroscopy results on the
heavy-fermion superconductor CeCoIn [1]. They obtained conductance spectra
on the c-axis surfaces of CeCoIn single crystals. Their major claims are
two-fold: CeCoIn has i) d-wave pairing symmetry and ii) two coexisting
order parameter components. In this Comment, we show that these claims are not
warranted by the data presented. [1] Rourke et al., Phys. Rev. Lett. 94, 107005
(2005).Comment: accepted for publication in Phys. Rev. Lett., final for
Finite volume corrections to the binding energy of the X(3872)
The quark mass dependence of hadrons is an important input for lattice
calculations. We investigate the light quark mass dependence of the binding
energy of the X(3872) in a finite box to next-to-leading order in an effective
field theory for the X(3872) with perturbative pions (XEFT). At this order, the
quark mass dependence is determined by a quark mass-dependent contact
interaction in addition to the one-pion exchange. While there is only a
moderate sensitivity to the light quark masses in the region up to twice their
physical value, the finite volume effects are significant already at box length
as large as 20 fm.Comment: 23 pages, 9 figures, REVTe
Magnetoresistance devices Progress report
Investigating galvanomagnetic effects in developing higher magnetoresistance devices for low voltage high current switche
The breakage prediction for hydromechanical deep drawing based on local bifurcation theory
A criterion of sheet metal localized necking under plane stress was established based on the bifurcation theory and the characteristics theory of differential equation. In order to be capable to incorporate the directional dependence of the plastic strain rate on stress rate, Ito-Goya’s constitutive equation which gave a one to one relationship between stress rate component and plastic strain rate component was employed. The hydromechanical deep drawing process of a cylindrical cup part was simulated using the commercial software ABAQUS IMPLICIT. The onset of breakage of the part during the forming process was predicted by combining the simulation results with the local necking criterion. The proposed method is applied to the hydro-mechanical deep drawing process for A2219 aluminum alloy sheet metal to predict the breakage of the cylindrical cup part. The proposed method can be applied to the prediction of breakage in the forming of the automotive bodies
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