2,793 research outputs found
Progenitor's signatures in Type Ia supernova remnants
The remnants of Type Ia supernovae can provide important clues about their
progenitor-histories. We discuss two well-observed supernova remnants (SNRs)
that are believed to result from a Type Ia SN and use various tools to shed
light on the possible progenitor history. We find that Kepler's SNR is
consistent with a symbiotic binary progenitor consisted of a white dwarf and an
AGB star. Our hydrosimulations can reproduce the observed kinematic and
morphological properties. For Tycho's remnant we use the characteristics of the
X-ray spectrum and the kinematics to show that the ejecta has likely interacted
with dense circumstellar gas.Comment: 4 pages, 9 figures, proceedings for IAU Symposium 281, Padova, July
201
C18O (3-2) observations of the Cometary Globule CG 12: a cold core and a C18O hot spot
The feasibility of observing the C18O (3-2) spectral line in cold clouds with
the APEX telescope has been tested. As the line at 329.330 GHz lies in the wing
of a strong atmospheric H2O absorption it can be observed only at high altitude
observatories. Using the three lowest rotational levels instead of only two
helps to narrow down the physical properties of dark clouds and globules. The
centres of two C18O maxima in the high latitude low mass star forming region CG
12 were mapped in C18O (3-2) and the data were analyzed together with spectral
line data from the SEST. The T_MB(3-2)/T_MB(2-1) ratio in the northern C18O
maximum, CG 12 N, is 0.8, and in the southern maximum, CG 12 S, ~2. CG 12 N is
modelled as a 120'' diameter (0.4pc) cold core with a mass of 27 Msun. A small
size maximum with a narrow, 0.8 kms-1, C18O (3-2) spectral line with a peak
temperature of T_MB ~11 K was detected in CG 12 S. This maximum is modelled as
a 60'' to 80'' diameter (~0.2pc) hot (80 K < Tex < 200 K) ~1.6 Msun clump. The
source lies on the axis of a highly collimated bipolar molecular outflow near
its driving source. This is the first detection of such a compact, warm object
in a low mass star forming region.Comment: APEX A&A special issue, accepte
Differentiability of fractal curves
While self-similar sets have no tangents at any single point, self-affine
curves can be smooth. We consider plane self-affine curves without double
points and with two pieces. There is an open subset of parameter space for
which the curve is differentiable at all points except for a countable set. For
a parameter set of codimension one, the curve is continuously differentiable.
However, there are no twice differentiable self-affine curves in the plane,
except for parabolic arcs
Far-Infrared Emission from Intracluster Dust in Abell Clusters
The ISOPHOT instrument aboard ISO has been used to observe extended FIR
emission of six Abell clusters. The raw profiles of the I_(120 um) / I_(180 um)
surface brightness ratio including zodiacal light show a bump towards Abell
1656 (Coma), dips towards Abell 262 and Abell 2670, and are without clear
structure towards Abell 400, Abell 496, and Abell 4038. After subtraction of
the zodiacal light, the bump towards Abell 1656 is still present, while the
dips towards Abell 262 and Abell 2670 are no longer noticable. This indicates a
localized excess of emitting material outside the Galaxy towards Abell 1656,
while the behavior in Abell 262 and Abell 2670 can be reconciled with galactic
cirrus structures localized on the line-of-sight to these clusters. The excess
towards Abell 1656 (Coma) is interpreted as thermal emission from intracluster
dust distributed in the hot X-ray emitting intracluster medium. The absence of
any signature for intracluster dust in five clusters and the rather low
inferred dust mass in Abell 1656 indicates that intracluster dust is likely not
responsible for the excess X-ray absorption seen in cooling flow clusters.
These observations thereby represent a further unsuccessful attempt in
detecting the presumed final stage of the cooling flow material, in accord with
quite a number of previous studies in other wavelengths regions. Finally, the
observed dimming of the high-redshift supernovae is unlikely be attributable to
extinction caused by dust in the intracluster or even a presumed intercluster
medium.Comment: 16 pages, 32 figures, accepted for publication in Astronomy &
Astrophysic
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