118,982 research outputs found
What can we learn from three-pion interferometry ?
We address the question which additional information on the source shape and
dynamics can be extracted from three-particle Bose-Einstein correlations. For
chaotic sources the true three-particle correlation term is shown to be
sensitive to the momentum dependence of the saddle point of the source and to
its asymmetries around that point. For partially coherent sources the
three-pion correlator allows to measure the degree of coherence without
contamination from resonance decays. We derive the most general Gaussian
parametrization of the two- and three-particle correlator for this case and
discuss the space-time interpretation of the corresponding parameters.Comment: 16 pages, to be published in Phys. Rev.
Chromospheric evaporation in sympathetic coronal bright points
{Chromospheric evaporation is a key process in solar flares that has
extensively been investigated using the spectroscopic observations. However,
direct soft X-ray (SXR) imaging of the process is rare, especially in remote
brightenings associated with the primary flares that have recently attracted
dramatic attention.} {We intend to find the evidence for chromospheric
evaporation and figure out the cause of the process in sympathetic coronal
bright points (CBPs), i.e., remote brightenings induced by the primary CBP.}
{We utilise the high-cadence and high-resolution SXR observations of CBPs from
the X-ray Telescope (XRT) aboard the Hinode spacecraft on 2009 August 23.} {We
discover thermal conduction front propagating from the primary CBP, i.e., BP1,
to one of the sympathetic CBPs, i.e., BP2 that is 60\arcsec away from BP1.
The apparent velocity of the thermal conduction is 138 km s.
Afterwards, hot plasma flowed upwards into the loop connecting BP1 and BP2 at a
speed of 76 km s, a clear signature of chromospheric evaporation.
Similar upflow was also observed in the loop connecting BP1 and the other
sympathetic CBP, i.e., BP3 that is 80\arcsec away from BP1, though less
significant than BP2. The apparent velocity of the upflow is 47 km
s. The thermal conduction front propagating from BP1 to BP3 was not well
identified except for the jet-like motion also originating from BP1.} {We
propose that the gentle chromospheric evaporation in the sympathetic CBPs were
caused by thermal conduction originating from the primary CBP.}Comment: 9 pages, 5 figure
Remote multispectral imaging with PRISMS and XRF analysis of Tang Tomb paintings
PRISMS (Portable Remote Imaging System for Multispectral Scanning) is a multispectral/hyperspectral imaging system designed for flexible in situ imaging of wall paintings at high resolution (tens of microns) over a large range of distances (less than a meter to over ten meters). This paper demonstrates a trial run of the VIS/NIR (400-880nm) component of the instrument for non-invasive imaging of wall paintings in situ. Wall painting panels from excavated Tang dynasty (618-907AD) tombs near Xi’an were examined by PRISMS. Pigment identifications were carried out using the spectral reflectance obtained from multispectral imaging coupled with non-invasive elemental analysis using a portable XRF
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