9,646 research outputs found
The Distance and Age of the SNR Kes 73 and AXP 1E 1841-045
We provide a new distance estimate to the supernova remnant (SNR) Kes 73 and
its associated anomalous X-ray pulsar (AXP) 1E 1841-045. 21 cm HI images and HI
absorption/ emission spectra from new VLA observations, and 13CO emission
spectra of Kes 73 and two adjacent compact HII regions (G27.276+0.148 and
G27.491+0.189) are analyzed. The HI images show prominent absorption features
associated with Kes 73 and the HII regions. The absorption appears up to the
tangent point velocity giving a lower distance limit to Kes 73 of 7.5 kpc,
which has previously been given as the upper limit. Also, G27.276+0.148 and
G27.491+0.189 are at the far kinematic distances of their radio recombination
line velocities. There is prominent HI emission in the range 80--90 km/s for
all three objects. The two HII regions show HI absorption at ~ 84 km/s, but
there is no absorption in the Kes 73 absorption spectrum. This implies an upper
distance limit of ~ 9.8 kpc to Kes 73. This corrected larger distance to Kes
73/ AXP 1E 1841-045 system leads to a refined age of the SNR of 500 to 1000 yr,
and a ~ 50% larger AXP X-ray luminosity.Comment: 10 pages, 2 figures, ApJ, dol:10.1086/"529120
Shocked H2 and Fe+ Dynamics in the Orion Bullets
Observations of H2 velocity profiles in the two most clearly defined Orion
bullets are extremely difficult to reconcile with existing steady-state shock
models. We have observed [FeII] 1.644um velocity profiles of selected bullets
and H2 1-0 S(1) 2.122um velocity profiles for a series of positions along and
across the corresponding bow-shaped shock fronts driven into the surrounding
molecular cloud. Integrated [FeII] velocity profiles of the brightest bullets
are consistent with theoretical bow shock predictions. However, observations of
broad, singly-peaked H2 1-0 S(1) profiles at a range of positions within the
most clearly resolved bullet wakes are not consistent with molecular shock
modelling. A uniform, collisionally broadened background component which
pervades the region in both tracers is inconsistent with fluorescence due to
the ionizing radiation of the Trapezium stars alone.Comment: 20 pages including 18 figures, published in MNRA
Development of life-test methodology for long-life mechanical components. Phase 1: Development of methodology
The Distances of SNR W41 and overlapping HII regions
New HI images from the VLA Galactic Plane Survey show prominent absorption
features associated with the supernovae remnant G23.3-0.3 (SNR W41). We
highlight the HI absorption spectra and the CO emission spectra of eight
small regions on the face of W41, including four HII regions, three non-thermal
emission regions and one unclassified region. The maximum velocity of
absorption for W41 is 782 km/s and the CO cloud at radial velocity
955 km/s is behind W41. Because an extended TeV source, a diffuse X-ray
enhancement and a large molecular cloud at radial velocity 775 km/s are
also projected at the center of W41, these yield the kinematic distance of 3.9
to 4.5 kpc for W41. For HII regions, our analyses reveal that both G23.42-0.21
and G23.07+0.25 are at the far kinematic distances (9.9 kpc and
10.6 kpc respectively) of their recombination-line velocities (1030.5 km/s
and 89.62.1 km/s respectively), G23.07-0.37 is at the near kinematic
distance (4.40.3 kpc) of its recombination-line velocity (82.72.0
km/s), and G23.27-0.27 is probably at the near kinematic distance (4.10.3
kpc) of its recombination-line velocity (76.10.6 km/s).Comment: 11 pages, 3 figs., 2 tables, accepted by A
A Precise Distance to IRAS 00420+5530 via H2O Maser Parallax with the VLBA
We have used the VLBA to measure the annual parallax of the H2O masers in the
star-forming region IRAS 00420+5530. This measurement yields a direct distance
estimate of 2.17 +/- 0.05 kpc (<3%), which disagrees substantially with the
standard kinematic distance estimate of ~4.6 kpc (according to the rotation
curve of Brand and Blitz 1993), as well as most of the broad range of distances
(1.7-7.7 kpc) used in various astrophysical analyses in the literature. The
3-dimensional space velocity of IRAS 00420+5530 at this new, more accurate
distance implies a substantial non-circular and anomalously slow Galactic
orbit, consistent with similar observations of W3(OH) (Xu et al., 2006;
Hachisuka et al. 2006), as well as line-of-sight velocity residuals in the
rotation curve analysis of Brand and Blitz (1993). The Perseus spiral arm of
the Galaxy is thus more than a factor of two closer than previously presumed,
and exhibits motions substantially at odds with axisymmetric models of the
rotating Galaxy.Comment: 33 pages, 12 figures; Accepted by ApJ (to appear March 2009
Development of life-test methodology for long-life mechanical components. Phase 1: Development of methodology. Phase 2: Demonstration of methodology
High resolution sub-millimetre mapping of starburst galaxies: Comparison with CO emission
Researchers present first results from a program of submillimeter continuum mapping of starburst galaxies, and comparison of their dust and CO emission. This project was prompted by surprising results from the first target, the nearby starburst M82, which shows in the dust continuum a morphology quite unlike that of its CO emission, in contrast to what might be expected if both CO and dust are accurately tracing the molecular hydrogen. Possible explanations for this striking difference are discussed. In the light of these results, the program has been extended to include sub-mm mapping of the nearby, vigorously star forming spirals, M83 and Maffei 2. The latter were also observed extensively in CO, in order to study excitation conditions in its central regions. The James Clerk Maxwell Telescope was used in these studies
Interaction Effects of 3-Mercaptohexan-1-ol (3MH), Linalool and Ethyl Hexanoate on the Aromatic Profile of South African Dry Chenin Blanc Wine by Descriptive Analysis (DA)
Interaction studies are some of the most interesting sensory experiments that highlight the effect of composition on wine perception. The use of single compounds, viz. an ester (ethyl hexanoate), a terpene (linalool) and a thiol (3-mercaptohexanol, 3MH), which have previously been shown to be representative of Chenin Blanc wines, resulted in typical descriptors for these compounds, such as ‘apple, ‘floral’ and ‘guava’ respectively. Interaction effects were observed between the compounds, and these were reflected in both the nature and the level of attributes generated. Additionally, interaction effects between the compounds (singles and combinations) and the wine matrix indicated that the latter plays an important role in theperception of wine aromas. The use of a dearomatised neutral wine base added an extra dimension to this study, which usually is done in a simpler matrix, such as a model wine
Determinação do poder calorÃfico de resÃduos florestais em função do seu teor de umidade.
Resumo
Trigonometric Parallaxes of Massive Star-Forming Regions. IX. The Outer Arm in the First Quadrant
We report a trigonometric parallax measurement with the Very Long Baseline
Array for the water maser in the distant high-mass star-forming region
G75.30+1.32. This source has a heliocentric distance of 9.25+-0.45 kpc, which
places it in the Outer arm in the first Galactic quadrant. It lies 200 pc above
the Galactic plane and is associated with a substantial HI enhancement at the
border of a large molecular cloud. At a Galactocentric radius of 10.7 kpc,
G75.30+1.32 is in a region of the Galaxy where the disk is significantly warped
toward the North Galactic Pole. While the star-forming region has an
instantaneous Galactic orbit that is nearly circular, it displays a significant
motion of 18 km/s toward the Galactic plane. The present results, when combined
with two previous maser studies in the Outer arm, yield a pitch angle of about
12 degrees for a large section of the arm extending from the first quadrant to
the third.Comment: 19 pages, 5 figures, 4 tables, accepted by The Astrophysical Journa
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