285 research outputs found
Discovery of a New Supernova Remnant in the Direction of G69.7+1.0
We discovered a middle-aged supernova remnant (SNR) in the vicinity of
G69.7+1.0 using the ASCA satellite. G69.7+1.0 was identified in the 2.7 GHz
survey and classified as a shell-type SNR with a diameter of 16 arcmin. During
the ROSAT all-sky survey, the X-ray emission was detected in the direction of
G69.7+1.0. However, it extends beyond the radio shell, and an X-ray bright
region was located outside of the radio shell. A spectral study with the ASCA
and ROSAT shows a thin thermal plasma with an electron temperature of ~0.4 keV.
There is no significant variation of the spectral parameters over the field of
view, except for the lower column density of the eastern part. We also found a
large shell structure which surrounds the X-ray bright region in both optical
and radio images. We suggest that the observed X-ray emission is associated
with the large optical and radio shell, and that they are part of a new SNR,
different from the radio SNR G69.7+1.0, which we have named AX J2001+3235 or
G69.4+1.2. The large shell and the electron temperature of ~0.4 keV indicate
that AX J2001+3235 is an evolved SNR. From a comparison with the column density
of CTB 80 (G69.0+2.7), we estimate that the distance of the SNR is about 2.5
kpc.Comment: Accepted for publication in PASJ, 9 pages, 5 figure
Spatially Resolved Spectral Analysis of Vela Shrapnel D
The ROSAT all-sky survey discovered several `shrapnels', showing boomerang
structures outside the Vela supernova remnant. We observed shrapnel D with the
XMM-Newton satellite. There is an X-ray bright ridge structure in our FOV
running from north to south. Applying the VNEI model to X-ray spectra of
various regions, we find that the plasma in the eastern part from the X-ray
ridge is significantly different from that in the western part. The X-ray
spectra in the western part can be represented by a single-temperature
component. The abundances of heavy elements are almost uniform, whereas they
are heavily overabundant, except for Fe; the relative abundances to the solar
values are O about 5, Ne about 10, Mg about 10, Fe about 1. This indicates that
shrapnel D originated from the ejecta of the supernova. We find that the plasma
in the eastern part from the ridge consists of two components with different
temperatures; the hot component comes from the ejecta, while the cold component
comes from the interstellar matter. These two components are considered to be
in contact with each other, forming a contact discontinuity. Around the
northern part of the contact discontinuity, we find wave-like structures of
which the typical scale are comparable with that of the Rayleigh--Taylor
instability.Comment: 15 pages, 14 figure
High-Resolution X-Ray Spectroscopy of Galactic Supernova Remnants
High-resolution X-ray spectroscopy of Galactic supernova remnants (SNRs), based on grating spectrometers onboard XMM-Newton and Chandra, has been revealing a variety of new astrophysical phenomena. Broadened oxygen lines for a northwestern compact knot in SN 1006 clearly show a high oxygen temperature of ~300 keV. The high temperature together with a lower electron temperature (kTe ~ 1 keV) can be reasonably interpreted as temperature non-equilibration between electrons and oxygen behind a collisionless shock. An ejecta knot in the Puppis A SNR shows blueshifted line emission by ~ 1500kms-1. The line widths are fairly narrow in contrast to the SN 1006's knot; an upper limit of 0.9 eV is obtained for O VIII Lyα, which translates to an oxygen temperature of kTO < 30 keV. The low temperature suggests that the knot was heated by a reverse shock whose velocity is 4 times slower than that of a forward shock. Anomalous intensity ratios in O VII Heα lines, i.e., a stronger forbidden line than a resonance line, is found in a cloud-shock interaction region in Puppis A. The line ratio can be best explained by the charge-exchange emission that should arise at interfaces between the cold/warm clouds and the hot plasma. There are several other targets for which we plan to analyze high-quality grating data prior to the operation of the soft X-ray spectrometer onboard Astro-H
Overabundance of Calcium in the young SNR RX J08524622: evidence of over-production of Ti
Recently, COMPTEL has detected -rays of 1157 keV from Ti in
the direction of the SNR RX J08524622 (Iyudin et al. 1998). Since Ti
is a product of explosive nucleosynthesis and its half lifetime \tau\sb{1/2}
is about 60 yrs, RX J08524622 must be a young supernova remnant and
radiation is dominated by the ejecta rather than by interstellar matter. We
have detected an X-ray emission line at keV which is thought to
come from highly ionized Ca. The emission line is so far only seen in the
north-west shell region of RX J08524622. The X-ray spectrum can be well
fitted with that of thin hot plasma of cosmic abundances except that of Ca,
which is overabundant by a factor of . Assuming that most of Ca is
Ca, which originates from Ti by radioactive decay, we estimate a
total Ca mass of about . Combining the amount of
Ca and the observed flux of the Ti -ray line, the age of
RX J08524622 is around 1000 yrs.Comment: 14 pages, 5figures, accepted for publication of PAS
The Ejecta Distributions of the Heavy Elements in the Cygnus Loop
We analyzed the metal distribution of the Cygnus Loop using 14 and 7
pointings observation data obtained by the \textit{Suzaku} and the
\textit{XMM-Newton} observatories. The spectral analysis shows that all the
spectra are well fitted by the two- non-equilibrium ionization plasma
model as shown by the earlier observations. From the best-fit parameters of the
high- component, we calculated the emission measures about various
elements and showed the metal distribution of the ejecta component. We found
that the distributions of Si and Fe are centered at the southwest of the
geometric center toward the blow-out region. From the best-fit parameters, we
also estimated the progenitor mass of the Cygnus Loop from our field of view
and the metal rich region with a radius of 25 arcmin from the metal center. The
result from the metal circle is similar to that from our entire FOV, which
suggests the mixing of the metal. From the results, we estimated the mass of
the progenitor star at 12-15\MO.Comment: 15 pages, 5 figures, PASJ, Vol.61, No.
In Orbit Performance of the MAXI/SSC onboard the ISS
We report here the in orbit performance of the CCD camera (MAXI/SSC) onboard
the International Space Station (ISS). It was commissioned in August, 2009.
This is the first all-sky survey mission employing X-ray CCDs. It consists of
32 CCDs each of which is 1 inch square. It is a slit camera with a field of
view of 1deg.5x 90deg and scans the sky as the rotation of the ISS. The CCD on
the SSC is cooled down to the working temperature around -60degC by the
combination of the peltier cooler, a loop heat pipe and a radiator. The
standard observation mode of the CCD is in a parallel sum mode (64-binning).
The CCD functions properly although it suffers an edge glow when the Sun is
near the field of view (FOV) which reduces the observation efficiency of the
SSC down to about 30%. The performance of the CCD is continuously monitored
both by the Mn-K X-rays and by the Cu-K X-rays. There are many sources
detected, not only point sources but extended sources. Due to the lack of the
effective observation time, we need more observation time to obtain an extended
emission analysis extraction process.Comment: 15 pages 11 figure
ASCA Observation of the Crab-Like Supernova Remnant 3C58
We present here the X-ray observation of a Crab-like supernova remnant (SNR)
3C58 with ASCA. We find that the integrated energy spectrum over the nebula is
consistent with previous results, showing a power-law spectrum with the photon
index modified by interstellar absorption of about
. Inclusion of a blackbody component which is
attributable to the central compact source significantly improves the spectral
fit. Stringent upper limits for any line emitting thin hot plasma are
established. We find for the first time that the nebular spectrum is harder in
the central part of the SNR, becoming softer toward the periphery, while the
absorption column is uniform across the nebula. Correspondingly, the nebular
size decreases with increasing photon energy which is a steeper function of
radius than that of the Crab nebula. The results are compared with synchrotron
energy loss models and the nature of the putative pulsar is discussed. Timing
analysis was performed to search for pulsed X-ray emission from the central
compact source. No significant pulsations are observed, and we present the
upper limit for the pulsed fraction.Comment: 27 pages, 7 figures, to appear in PAS
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