2003 Fiscal Year Final Research Report Summary
A Study of Mass-Loss from Red Giant Stars Based on Super High Resolution Optical Spectroscopy
| Project/Area Number |
13640247
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Astronomy
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| Research Institution | National Astronomical Observatory of Japan |
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Principal Investigator |
IZUMIURA Hideyuki National Astronomical Observatory, Okayama Astrophysical Observatory, Chief Research, 岡山天体物理観測所, 主任研究員 (00211730)
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| Co-Investigator(Kenkyū-buntansha) |
NOGUCHI Kunio National Astronomical Observatory, Optical and Infrared Astronomy Division, Professor, 光赤外研究部, 教授 (10111824)
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| Project Period (FY) |
2001 – 2003
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| Keywords | mass loss / circumstellar / C_2 / Swan band / carbon stars / silicate / binary / accretion disk |
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| Research Abstract |
Circumstellar(CS) C_2 Swan band absorption lines were detected for the fast time in optical carbon stars using HIDES spectrometer on the 188cm reflector at Okayama Astrophysical Observatory. On the basis of this discovery, we have performed a systematic survey of CS C_2 absorption lines and made a quantitative analysis of the C_2 absorption lines. We have obtained a sample of 44 stars, among which 17 stars show definite CS C_2 lines. It is found that CS C_2 lines are seen in stars having effective temperature lower than 2800K and a C/O ratio greater than 1.1. A very high accuracy as high as 〜 20 m/s is achieved in radial velocity measurements of the CS C_2 gas. Rotational excitation temperature of the C_2 gas locates the gas layer in the circumstellar region, somewhere between several tens and a hundred stellar radii. Estimated abundances of the CS C_2 gas suggest that the CS C_2 form from C_2H_2 in the outflows through photo-dissociation by the interstellar radiation field. The CS C_2 gas may be a new optical probe of the region with radii of 〜10^<15> cm from the central star. It would also be possible to derive carbon isotopic ratios in these stars, and similar analyses would be applicable to Mira-type carbon stars. We have not detected, however, similar CS absorption lines by polyatomic molecules such as C_3 or SiC_2 in carbon stars or by some molecules in oxygen-rich stars. We have also discovered Balmer and Paschen continuum emission and Balmer series lines with P-Cyg profile in the silicate carbon star, BM Gem. On the basis of the energetics, the hypothesis that BM Gem has a companion that gives rise to an accretion disk that accelerates the observed high velocity outflow can be understood consistently. The results show that the existence of a companion plays an important role in the silicate carbon star phenomena.
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Research Products
(6 results)
