5,497 research outputs found
Hard X-ray emission cutoff in anomalous X-ray pulsar 4U 0142+61 detected by INTEGRAL
The anomalous X-ray pulsar 4U 0142+61 was studied by the INTEGRAL
observations. The hard X-ray spectrum of 18 -- 500 keV for 4U 0142+61 was
derived using near 9 years of INTEGRAL/IBIS data. We obtained the average hard
X-ray spectrum of 4U 0142+61 with all available data. The spectrum of 4U
0142+61 can be fitted with a power-law with an exponential high energy cutoff.
This average spectrum is well fitted with a power-law of plus a cutoff energy at keV. The hard X-ray flux of the
source from 20 -- 150 keV showed no significant variations (within 20) from
2003 -- 2011. The spectral profiles have some variability in nine years: photon
index varied from 0.3 -- 1.5, and cutoff energies of 110 -- 250 keV. The
detection of the high energy cutoff around 130 keV shows some constraints on
the radiation mechanisms of magnetars and possibly probes the differences
between magnetar and accretion models for these special class of neutron stars.
Future HXMT observations could provide stronger constraints on the hard X-ray
spectral properties of this source and other magnetar candidates.Comment: 9 pages, 5 figures, 2 tables, figures are updated, new data are
added, conclusion does not change, to be published in RA
Entanglement distribution over the subsystems and its invariance
We study the entanglement dynamics of two qubits, each of which is embedded
into its local amplitude-damping reservoir, and the entanglement distribution
among all the bipartite subsystems including qubit-qubit, qubit-reservoir, and
reservoir-reservoir. It is found that the entanglement can be stably
distributed among all components, which is much different to the result
obtained under the Born-Markovian approximation by C. E. L\'{o}pez {\it et al.}
[Phys. Rev. Lett. \textbf{101}, 080503 (2008)], and particularly it also
satisfies an identity. Our unified treatment includes the previous results as
special cases. The result may give help to understand the physical nature of
entanglement under decoherence.Comment: 6 pages, 5 figure
Generating Many Majorana Modes via Periodic Driving: A Superconductor Model
Realizing Majorana modes (MMs) in condensed-matter systems is of vast
experimental and theoretical interests, and some signatures of MMs have been
measured already. To facilitate future experimental observations and to explore
further applications of MMs, generating many MMs at ease in an experimentally
accessible manner has become one important issue. This task is achieved here in
a one-dimensional -wave superconductor system with the nearest- and
next-nearest-neighbor interactions. In particular, a periodic modulation of
some system parameters can induce an effective long-range interaction (as
suggested by the Baker-Campbell-Hausdorff formula) and may recover
time-reversal symmetry already broken in undriven cases. By exploiting these
two independent mechanisms at once we have established a general method in
generating many Floquet MMs via periodic driving.Comment: 5 pages, 3 figures. To appear in Phys. Rev. B as a Rapid
Communicatio
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