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Observational Study of the Water Maser Burst in the Orion-KL Region
https://ir.soken.ac.jp/records/401
https://ir.soken.ac.jp/records/401f648c1bb-2ec7-4fd3-84eb-d9742ad7768d
| 名前 / ファイル | ライセンス | アクション |
|---|---|---|
要旨・審査要旨 / Abstract, Screening Result (281.1 kB)
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| Item type | 学位論文 / Thesis or Dissertation(1) | |||||
|---|---|---|---|---|---|---|
| 公開日 | 2010-02-22 | |||||
| タイトル | ||||||
| タイトル | Observational Study of the Water Maser Burst in the Orion-KL Region | |||||
| タイトル | ||||||
| タイトル | Observational Study of the Water Maser Burst in the Orion-KL Region | |||||
| 言語 | en | |||||
| 言語 | ||||||
| 言語 | eng | |||||
| 資源タイプ | ||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_46ec | |||||
| 資源タイプ | thesis | |||||
| 著者名 |
望月, 奈々子
× 望月, 奈々子 |
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| フリガナ |
モチズキ, ナナコ
× モチズキ, ナナコ |
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| 著者 |
MOCHIZUKI, Nanako
× MOCHIZUKI, Nanako |
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| 学位授与機関 | ||||||
| 学位授与機関名 | 総合研究大学院大学 | |||||
| 学位名 | ||||||
| 学位名 | 博士（理学） | |||||
| 学位記番号 | ||||||
| 内容記述タイプ | Other | |||||
| 内容記述 | 総研大甲第553号 | |||||
| 研究科 | ||||||
| 値 | 数物科学研究科 | |||||
| 専攻 | ||||||
| 値 | 09 天文科学専攻 | |||||
| 学位授与年月日 | ||||||
| 学位授与年月日 | 2001-09-28 | |||||
| 学位授与年度 | ||||||
| 値 | 2001 | |||||
| 要旨 | ||||||
| 内容記述タイプ | Other | |||||
| 内容記述 | In December 1997 we discovered the enormous outburst of the water maser source in the nearest massive star forming region Orion-KL. The intensity of the burst maser shows nearly exponential increase up to a few 10 6 Jy and lasted for a year. Though the water maser burst in the Orion-KL region was also reported in 20 years ago, the monitoring observations of the previous maser burst were only obtained by single-dish radio telescopes, thus the spatial distribution and time variation were unknown and the amplification mechanisms of the water maser burst are still unclear. In order to investigate the time variation of the spatial distribution of the burst region, we conducted a series of VLBI monitoring observations, especially onset of the burst and enormous increasing period of the burst, toward the region using Japanese domestic VLBI network called J-Net. We determined the absolute position of the burst maser feature by the fringe-rate mapping method with 1 arcsec accuracy. The position of the burst maser feature is about 4000 AU southwest of IRc2 and compared with the previous results of the burst occurred in the Orion-KL 20 years ago, we found the burst occurred repeatedly in the same region. The apparent shifts in the peak velocity and line narrowing in the initial stage of the amplification have been reported in observations of the previous maser bursts. Our total power spectra obtained with Kashima 34-m telescope showed apparent shift in the peak velocity and narrowing of the burst line, too. However, no shift in the peak velocity nor narrowing was detected in our VLBI cross-power spectra of the burst maser feature ( V LSR～7.68 km/s , ΔV ～0.38 km/s ). The absence of the narrowing required that the burst maser must be saturated and must be caused by the beaming but not by the intensity variation of the input source. The apparent phenomena are well explained by the varying weight of the burst feature among other largely stationary features. From the spatial distribution, the burst feature is about 5 AU in size and is elongated in the northwest-southeast direction. We found a clear velocity gradient in the velocity channel components (spots) of the masers. Redder spots were located in the northwest and bluer spots are located in the southeast of the burst feature. Comparison of the spatial distribution of our multi-epoch VLBI observations revealed that most of the maser spots in the burst feature show apparent movements relative to the 7.6km/s burst spot. In the region of the vicinity of the burst feature, there are five maser features with LSR velocity within a few km/s around the velocity of the burst feature (7.3 km/s) aligned linearly in the northwest-southeast direction with spatial extension of 200 AU from the burst feature. Two of the maser features in the linear structure are very similar to those observed in the quiescent period. It is most likely that they are the same maser features. These results indicate that the beaming in the two overlapping masing regions caused a mechanism of the enormous amplification, and this is consistent with the interacting maser model. It seems therefore natural to seek for a possible relationship between linear structure of the burst region in 100 AU scale and a mechanism, which causes the maser burst. Based on the interacting maser model, in order to explain the overlapping of two maser features along our line of sight, we consider a possibility of the model that assumes the 100 AU scale northwest -southeast structure as an edge-on view of a large rotating disk. Some features could be explained. However, the velocity difference among the linear aligned features is difficult to explain. It seems to be consider the structure as another possibility that the overlapping of two maser features is caused by a compact maser source and a steady large-scale flow such as the shocked layer may be formed by the high velocity flow from the source I which shows a characteristic bend in this region. |
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| 所蔵 | ||||||
| 値 | 有 | |||||
| フォーマット | ||||||
| 内容記述タイプ | Other | |||||
| 内容記述 | application/pdf | |||||
