410 research outputs found
Chandra Observation of the Anomalous X-ray Pulsar 1E 1841-045
We present the results from the {\it Chandra} ACIS CC mode observation of an
anomalous X-ray pulsar (AXP) 1E 1841-045. This is the first observation in
which the pulsar spectrum in wide energy range is spatially discriminated from
the surrounding SNR, Kes 73. Like other AXPs, the phase-integrated spectrum is
fitted well with power-law plus blackbody model. The spectral parameters are
, keV, and . This photon index is
significantly flatter than the other AXPs, and resemble to soft gamma-ray
repeaters (SGRs) in the quiescent state. The pulse profile is double-peaked,
and we found that the second peak has significantly hard spectrum. The spectra
of all phases are consistent with power-law plus blackbody model with constant
temperature and photon index. When fitted with two blackbody model, we obtained
similarly good fit. These results can be interpreted that there are two
emission regions with different energy spectra.Comment: 4 pages, 4 figures, accepted for publication in PASJ Letter
User-Adaptive A Posteriori Restoration for Incorrectly Segmented Utterances in Spoken Dialogue Systems
Ideally, the users of spoken dialogue systems should be able to speak at their own tempo. Thus, the systems needs to interpret utterances from various users correctly, even when the utterances contain pauses. In response to this issue, we propose an approach based on a posteriori restoration for incorrectly segmented utterances. A crucial part of this approach is to determine whether restoration is required. We use a classification-based approach, adapted to each user. We focus on each user’s dialogue tempo, which can be obtained during the dialogue, and determine the correlation between each user’s tempo and the appropriate thresholds for classification. A linear regression function used to convert the tempos into thresholds is also derived. Experimental results show that the proposed user adaptation approach applied to two restoration classification methods, thresholding and decision trees, improves classification accuracies by 3.0% and 7.4%, respectively, in cross validation
X-ray Measurements of the Particle Acceleration Properties at Inward Shocks in Cassiopeia A
We present new evidence that the bright non-thermal X-ray emission features
in the interior of the Cassiopeia A supernova remnant (SNR) are caused by
inward moving shocks based on Chandra and NuSTAR observations. Several bright
inward-moving filaments were identified using monitoring data taken by Chandra
in 2000-2014. These inward-moving shock locations are nearly coincident with
hard X-ray (15-40 keV) hot spots seen by NuSTAR. From proper motion
measurements, the transverse velocities were estimated to be in the range
2,100-3,800 km s for a distance of 3.4 kpc. The shock velocities
in the frame of the expanding ejecta reach values of 5,100-8,700 km
s, slightly higher than the typical speed of the forward shock.
Additionally, we find flux variations (both increasing and decreasing) on
timescales of a few years in some of the inward-moving shock filaments. The
rapid variability timescales are consistent with an amplified magnetic field of
0.5-1 mG. The high speed and low photon cut-off energy of the
inward-moving shocks are shown to imply a particle diffusion coefficient that
departs from the Bohm regime ( 3-8) for the few
simple physical configurations we consider in this study. The maximum electron
energy at these shocks is estimated to be 8-11 TeV, smaller than the
values of 15-34 TeV inferred for the forward shock. Cassiopeia A is
dynamically too young for its reverse shock to appear to be moving inward in
the observer frame. We propose instead that the inward-moving shocks are a
consequence of the forward shock encountering a density jump of 5-8
in the surrounding material.Comment: 16 pages, 8 figures, accepted for publication in Ap
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