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N. Kameswara Rao V. R. Venugopal A. Patnaik 《Journal of Astrophysics and Astronomy》1985,6(3):153-157
VLA observations at 2 and 6 cm have been obtained for six hydrogen-deficient stars R CrB, HD 160641, BD — 9°4395, V348 Sgr,
MV Sgr and Sgrv Upper limits to the massloss rates have been estimated for some of these using the upper limits to the radio flux density.
National Radio Astronomy Observatory’s Very Large Array is operated by Associated Universities Inc. under contract with National
Science Foundation, USA 相似文献
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A simple analytical model of the particle-dominated outflow with zero total electric current from central rotating objects is considered. 'Exact' solutions for both relativistic and non-relativistic cases demonstrate the decollimation of the magnetic field lines in the region of the current closure. Such a decollimation can explain the presence of an energetic equatorial wind observed in many compact objects. 相似文献
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Spitzer observations of acetylene bands in carbon-rich asymptotic giant branch stars in the Large Magellanic Cloud 总被引:1,自引:0,他引:1
M. Matsuura P. R. Wood G. C. Sloan A. A. Zijlstra J. Th. van Loon M. A. T. Groenewegen J. A. D. L. Blommaert M.-R. L. Cioni M. W. Feast H. J. Habing S. Hony E. Lagadec C. Loup J. W. Menzies L. B. F. M. Waters P. A. Whitelock 《Monthly notices of the Royal Astronomical Society》2006,371(1):415-420
We investigate the molecular bands in carbon-rich asymptotic giant branch (AGB) stars in the Large Magellanic Cloud (LMC), using the Infrared Spectrograph (IRS) onboard the Spitzer Space Telescope ( SST ) over the 5–38 μm range. All 26 low-resolution spectra show acetylene (C2 H2 ) bands at 7 and 14 μm. The hydrogen cyanide (HCN) bands at these wavelengths are very weak or absent. This is consistent with low nitrogen abundances in the LMC. The observed 14 μm C2 H2 band is reasonably reproduced by an excitation temperature of 500 K. There is no clear dilution of the 14 μm C2 H2 band by circumstellar dust emission. This 14-μm band originates from molecular gas in the circumstellar envelope in these high mass-loss rate stars, in agreement with previous findings for Galactic stars. The C2 H2 column density, derived from the 13.7 μm band, shows a gas mass-loss rate in the range 3 × 10−6 to 5 × 10−5 M⊙ yr−1 . This is comparable with the total mass-loss rate of these stars estimated from the spectral energy distribution. Additionally, we compare the line strengths of the 13.7 μm C2 H2 band of our LMC sample with those of a Galactic sample. Despite the low metallicity of the LMC, there is no clear difference in the C2 H2 abundance among LMC and Galactic stars. This reflects the effect of the third dredge-up bringing self-produced carbon to the surface, leading to high carbon-to-oxygen ratio at low metallicity. 相似文献
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