943 research outputs found
Discovery of Enhanced Radiative Recombination Continua of He-like Iron and Calcium from IC 443 and Its Implications
We present deep observations of the Galactic supernova remnant IC 443 with
the {\it Suzaku X-ray satellite}. We find prominent K-shell lines from iron and
nickel, together with a triangle residual at 8--10~keV, which corresponds to
the energy of the radiative recombination continuum (RRC) of He-like iron. In
addition, the wavy residuals have been seen at 5.1 and 5.5~keV. We
confirm that the residuals show the first enhanced RRCs of He- and H-like
calcium found in supernova remnants. These facts provide robust evidence for
the recombining plasma. We reproduce the plasma in the 3.7--10~keV band using a
recombining plasma model at the electron temperature 0.65~keV. The
recombination parameter ( is electron density and
is elapsed time after formation of a recombining plasma) and abundances of iron
and nickel are strongly correlated, and hence the errors are large. On the
other hand, the ratio of nickel to iron relative to the solar abundances is
well constrained to 11 (1). A possibility is that the large
abundance ratio is a result of an asymmetric explosion of the progenitor star.Comment: 4 pages, 5 figures, published in Ap
Heat equation on the hypergraph containing vertices with given data
This paper is concerned with the Cauchy problem of a multivalued ordinary
differential equation governed by the hypergraph Laplacian, which describes the
diffusion of ``heat'' or ``particles'' on the vertices of hypergraph. We
consider the case where the heat on several vertices are manipulated internally
by the observer, namely, are fixed by some given functions. This situation can
be reduced to a nonlinear evolution equation associated with a time-dependent
subdifferential operator, whose solvability has been investigated in numerous
previous researches. In this paper, however, we give an alternative proof of
the solvability in order to avoid some complicated calculations arising from
the chain rule for the time-dependent subdifferential. As for results which
cannot be assured by the known abstract theory, we also discuss the continuous
dependence of solution on the given data and the time-global behavior of
solution.Comment: 19 pages, 3 figure
Time Variability of Nonthermal X-ray Stripes in Tycho's Supernova Remnant with Chandra
Analyzing Chandra data of Tycho's supernova remnant (SNR) taken in 2000,
2003, 2007, 2009, and 2015, we search for time variable features of synchrotron
X-rays in the southwestern part of the SNR, where stripe structures of hard
X-ray emission were previous found. By comparing X-ray images obtained at each
epoch, we discover a knot-like structure in the northernmost part of the stripe
region became brighter particularly in 2015. We also find a bright filamentary
structure gradually became fainter and narrower as it moved outward. Our
spectral analysis reveal that not only the nonthermal X-ray flux but also the
photon indices of the knot-like structure change from year to year. During the
period from 2000 to 2015, the small knot shows brightening of and
hardening of . The time variability can be explained
if the magnetic field is amplified to and/or if
magnetic turbulence significantly changes with time.Comment: 8 pages, 3 figures, 2 tables, accepted for publication in Ap
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