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arXiv 1105.5202astro-ph.SRastro-ph.GA
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IRAS 18113-2503：喷射速度最快的饮水机？

IRAS 18113-2503: the water fountain with the fastest jet?

Jose F. Gomez, J. Ricardo Rizzo, Olga Suarez, Luis F. Miranda, Martin A. Guerrero, Gerardo Ramos-Larios

备注：
Accepted for publication at The Astrophysical Journal Letters (special EVLA issue)
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摘要：

我们目前的扩展甚大阵（EVLA）水脉泽观测在22 GHz的源IRAS 18113-2503。脉泽成分跨越了~500 km/s的非常高的速度范围，是银河系脉泽中发现的第二大，仅次于高质量恒星形成区W 49 N。脉泽成分被分成一个蓝移和一个红移的星团，两个星团之间的距离为0.12”。进一步的中红外和射电数据表明，IRAS 18113-2503是一颗后AGB星，因此是罕见的“喷泉”类的新成员。它是水脉泽中总速度扩散最大的演化天体，并且在其红移和蓝移瓣（~170 km/s）内具有最高的速度色散。大的总速度范围可能表明IRAS 18113-2503在已知的喷泉星中具有最快的喷流。另一方面，每个波瓣内的显著高速度分散可以解释为由质量喷射事件产生的激波，其速度增加到非常高的值，或者，由具有大开度角和/或旋进运动的射流中的投影效应产生的激波。

英文摘要：

We present Expanded Very Large Array (EVLA) water maser observations at 22 GHz toward the source IRAS 18113-2503. Maser components span over a very high velocity range of ~500 km/s, the second largest found in a Galactic maser, only surpassed by the high-mass star forming region W49N. Maser components are grouped into a blue and a redshifted cluster, separated by 0.12". Further mid-IR and radio data suggest that IRAS 18113-2503 is a post-AGB star, thus a new bona fide member of the rare class of "water fountains". It is the evolved object with the largest total velocity spread in its water masers, and with the highest velocity dispersion within its red- and blue-shifted lobes (~170 km/s). The large total velocity range of emission probably indicates that IRAS 18113-2503 has the fastest jet among the known water fountain stars. On the other hand, the remarkably high velocity dispersion within each lobe may be interpreted in terms of shocks produced by an episode of mass ejection whose velocity increased up to very high values or, alternatively, by projection effects in a jet with a large opening angle and/or precessing motions.

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