56,848 research outputs found
Relation of SiO maser emission to IR radiation in evolved stars based on the MSX observation
Based on the space MSX observation in bands A(8m), C(12m),
D(15m) and E(21m), and the ground SiO maser observation of evolved
stars by the Nobeyama 45-m telescope in the v=1 and v=2 J=1-0 transitions, the
relation between SiO maser emission and mid-IR continuum radiation is analyzed.
The relation between SiO maser emission and the IR radiation in the MSX bands
A, C, D and E is all clearly correlated. The SiO maser emission can be
explained by a radiative pumping mechanism according to its correlation with
infrared radiation in the MSX band A.Comment: 11 pages, 4 figures, to appear in ApJ
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Design of Power-Splitter With Selectable Splitting-Ratio Using Angled and Cascaded MMI-Coupler
A concept of power splitter with selectable splitting-ratios is proposed based on two multimode interference (MMI) sections connected by a phase-shifting region, in which phase-matching conditions can be fulfilled by using a simple angled section or alternatively using matched phase-shifters. The design example of an asymmetrical splitter (10 : 90) is optimized by using the transfer matrix method and three-dimensional full-vectorial beam propagation method. The numerical results reveal that a simple 1.2° angled section can yield a 10 : 90 splitter with an insertion loss of 0.74 dB and a total length of 192 μm. It is also shown that, for the cascaded MMI couplers based splitter, a more compact length of 58 μm with a lower insertion loss of 0.41 dB can be achieved. The fabrication tolerances are also investigated for the proposed asymmetrical power splitter
Dust in the Local Group
How dust absorbs and scatters starlight as a function of wavelength (known as
the interstellar extinction curve) is crucial for correcting for the effects of
dust extinction in inferring the true luminosity and colors of reddened
astrophysical objects. Together with the extinction spectral features, the
extinction curve contains important information about the dust size
distribution and composition. This review summarizes our current knowledge of
the dust extinction of the Milky Way, three Local Group galaxies (i.e., the
Small and Large Magellanic Clouds, and M31), and galaxies beyond the Local
Group.Comment: 21 pages, 11 figures; invited review article published in "LESSONS
FROM THE LOCAL GROUP -- A Conference in Honour of David Block and Bruce
Elmegreen" eds. Freeman, K.C., Elmegreen, B.G., Block, D.L. & Woolway, M.
(SPRINGER: NEW YORK), pp. 85-10
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