5,335 research outputs found
On the Nature of AX J2049.6+2939 and AX J2050.0+2914
AX J2049.6+2939 is a compact X-ray source in the vicinity of the southern
blow-up region of the Cygnus Loop supernova remnant (Miyata et al. 1998a). This
source was the brightest X-ray source inside the
Cygnus Loop observed during the ASCA survey project. The X-ray spectrum was
well fitted by a power-law function with a photon index of . Short-term timing analysis was performed and no coherent pulsation
was found. Follow-up observations with ASCA have revealed a large variation in
X-ray intensity by a factor of 50, whereas the spectral shape did not
change within the statistical uncertainties. In the second ASCA observation, we
found another X-ray source, AX J2050.0+2941, at the north east of AX
J2049.6+2939. During the three ASCA observations, the X-ray intensity of AX
J2050.0+2941 varied by a factor of 4. No coherent pulsations could be
found for AX J2050.0+2941.
We have performed optical photometric and spectroscopic observations in the
vicinity of AX J2049.6+2939 at the Kitt Peak National Observatory
(KPNO). As a result, all objects brighter than -band magnitude of 22 in
the error box can be identified with normal stars. Combined with the
X-ray results and the fact that there are no radio counterparts, AX
J2049.6+2939 is not likely to be either an ordinary rotation-powered pulsar
or an AGN. The nature of AX J2049.6+2939 is still unclear and further
observations over a wide energy band are strongly required.
As to AX J2050.0+2941, the long-term X-ray variability and the radio
counterpart suggests that it is an AGN.Comment: 23 pages, 4 figures, Accepted for publication by Astrophysical
Journa
Discovery of the compact X-ray source inside the Cygnus Loop
We detected an X-ray compact source inside the Cygnus Loop during the
observation project of the whole Cygnus Loop with the ASCA GIS. The source
intensity is 0.11 c s for GIS and 0.15 c s for SIS, which is the
strongest in the ASCA band. The X-ray spectra are well fitted by a power law
spectrum of a photon index of \error{-2.1}{0.1} with neutral H column of
(\error{3.1}{0.6}). Taking into account the
interstellar absorption feature, this source is X-ray bright mainly above 1 keV
suggesting either an AGN or a rotating neutron star. So far, we did not detect
intensity variation nor coherent pulsation mainly due to the limited
observation time. There are several optical bright stellar objects within the
error region of the X-ray image. We carried out the optical spectroscopy for
the brightest source (V=+12.6) and found it to be a G star. The follow up deep
observation both in optical and in X-ray wavelengths are strongly required.Comment: Accepted for Publications of the Astronomical Society of Japan 17
pages, 3 figur
Ionization States and Plasma Structures of Mixed-morphology SNRs Observed with ASCA
We present the results of a systematic study using ASCA of the ionization
state for six ``mixed-morphology'' supernova emnants (MMSNRs): IC 443, W49B,
W28, W44, 3C391, and Kes 27. MMSNRs show centrally filled thermal X-ray
emission, which contrasts to shell-like radio morphology, a set of
haracteristics at odds with the standard model of SNR evolution (e.g., the
Sedov model). We have therefore studied the evolution of the MMSNRs from the
ionization conditions inferred from the X-ray spectra, independent of X-ray
morphology. We find highly ionized plasmas approaching ionization equilibrium
in all the mmsnrs. The degree of ionization is systematically higher than the
plasma usually seen in shell-like SNRs. Radial temperature gradients are also
observed in five remnants, with cooler plasma toward the limb. In IC 443 and
W49B, we find a plasma structure consistent with shell-like SNRs, suggesting
that at least some MMSNRs have experienced similar evolution to shell-like
SNRs. In addition to the results above, we have discovered an ``overionized''
ionization state in W49B, in addition to that previously found in IC 443.
Thermal conduction can cause the hot interior plasma to become overionized by
reducing the temperature and density gradients, leading to an interior density
increase and temperature decrease. Therefore, we suggest that the
``center-filled'' X-ray morphology develops as the result of thermal
conduction, and should arise in all SNRs. This is consistent with the results
that MMSNRs are near collisional ionization equilibrium since the conduction
timescale is roughly similar to the ionization timescale. Hence, we conclude
that MMSNRs are those that have evolved over yr. We call this phase
as the ``conduction phase.''Comment: 34 pages, 20 figures, 9 tables, accepted for publication in The
Astrophysical Journa
Physical Relation of Source I to IRc2 in the Orion KL Region
We present mid-infrared narrow-band images of the Orion BN/KL region, and
N-band low-resolution spectra of IRc2 and the nearby radio source "I." The
distributions of the silicate absorption strength and the color temperature
have been revealed with a sub-arcsecond resolution. The detailed structure of
the 7.8 micron/12.4 micron color temperature distribution was resolved in the
vicinity of IRc2. A mid-infrared counterpart to source I has been detected as a
large color temperature peak. The color temperature distribution shows an
increasing gradient from IRc2 toward source I, and no dominant temperature peak
is seen at IRc2. The spectral energy distribution of IRc2 could be fitted by a
two-temperature component model, and the "warmer component" of the infrared
emission from IRc2 could be reproduced by scattering of radiation from source
I. IRc2 itself is not self-luminous, but is illuminated and heated by an
embedded luminous young stellar object located at source I.Comment: 20 pages, 11 figures. Minor corrections had been done in the ver.2.
Accepted for publication in PAS
Experimental analysis of vacuum pressure and gas flow rate in structured-core transparent vacuum insulation panels
The notion that modern buildings should strive to be net-zero energy buildings (NZEBs) is widely accepted. One of the causes leading to high energy usage for space heating, resulting in avoidable carbon emissions, is heat loss via building windows. In order to improve windowâs insulation in existing buildings, structured-core transparent vacuum insulation panels (TVIPs) are proposed. TVIPs mainly consist of the structured core material, the low-emissivity film, and the transparent gas barrier envelope. TVIPs have high insulation performance and are inexpensive to manufacture and can be easily installed. Therefore, TVIPs have the potential to improve windowâs insulation in existing buildings at a low cost. However, it is necessary to overcome the issue of preventing the pressure rise inside TVIP after vacuum sealing. The authors constructed an experimental setup to quantify the effect of reduction of gas flow rate in TVIP after evacuation by applying the pressure-rate-of-rise-method. In this experiment, a gas barrier film with a straw was used as the vacuum chamber. This could reproduce the pressure increase in the TVIP after sealing and the gas flow rate in the TVIP is evaluated. The experimental result shows that the coated core material and the enclosing getter agent lowered the pressure rise and gas flow rate in TVIP by combining concurrent evacuation and heating. Furthermore, after extending the simultaneous vacuuming and heating period to 8 h and applying the coated core material, and enclosing the getter agent, the internal pressure in TVIP may be lowered to around 1 Pa after 30 min after halting vacuuming. It was confirmed that this pressure satisfied the performance required for TVIPs, and the result was much closer to the realization of TVIPs
X-ray Emitting Ejecta in Puppis A Observed with Suzaku
We report the detection and localization of X-ray emitting ejecta in the
middle-aged Galactic supernova remnant Puppis A using five observations with
the Suzaku X-ray Imaging Spectrometer to survey the eastern and middle portions
of the remnant. A roughly 3' by 5', double-peaked region in the north center is
found to be highly enriched in Si and other elements relative to the rest of
the remnant. The X-ray fitted abundances are otherwise well below the solar
values. While the ejecta-enhanced regions show some variation of relative
element abundances, there is little evidence for a very strong enhancement of
one element over the others in the imaged portion of the remnant, except
possibly for a region of O and Ne enhancement in the remnant's south center.
There is no spatial correlation between the compact [O III] emitting ejecta
knots seen optically and the abundance enhancements seen in X-rays, although
they are located in the same vicinity. The map of fitted column density shows
strong variations across the remnant that echo earlier X-ray spectral hardness
maps. The ionization age (as fitted for single temperature models) is sharply
higher in a ridge behind the northeast-east boundary of the remnant, and is
probably related to the strong molecular cloud interaction along that boundary.
The temperature map, by comparison, shows relatively weak variations.Comment: 25 pages latex, 6 postscript figures; ApJ, in pres
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