First detection of CO lines in a water fountain star

	First detection of CO lines in a water fountain star
	He JH(何金华)1,2 ; Imai, H 3; Hasegawa, TI 1; Campbell, SW 1,4; Nakashima, J 5
刊名	ASTRONOMY & ASTROPHYSICS
	2008-09
卷号	488 期号:2 页码:L21-L24
关键词	stars : AGB and post-AGB stars : circumstellar matter stars : evolution stars : individual : IRAS 16342-3814 stars : winds, outflows radio lines : stars
ISSN号	0004-6361
通讯作者	He, JH (reprint author), Acad Sinica, Inst Astron & Astrophys, POB 23-141, Taipei 10617, Taiwan.
产权排序	第二完成单位
英文摘要	Context. Water fountain stars are very young post-AGB stars with high velocity water maser jets. They are the best objects in which to study the onset of bipolar jets from evolved stars due to their young dynamical ages. However, none of them has been observed in any thermal lines. Aims. We aim to search for CO lines in the water fountain star IRAS 16342-3814 and investigate the properties of its thermal gas. Methods. The proximity, peculiar stellar velocity and high Galactic latitude of IRAS 16342-3814 make a single dish observation possible. We use the Arizona Radio Observatory 10 m telescope to observe the CO J = 2-1 line and compare the line parameters with those of masers. Results. We report the detection of (12)CO and (13)CO J = 2-1 lines from IRAS 16342-3814. The inferred (12)CO mass loss rate is an order of magnitude lower than the infrared and OH mass loss rates, indicating a very cold and thick O-rich circumstellar envelope around the star. We also find a (12)CO expansion velocity of V(exp) = 46 +/- 1 km s(-1) that is too high for an AGB wind and confirm the systemic velocity of 44 +/- 1 km s(-1). In addition we measure a very low (12)CO/(13)CO line ratio of 1.7. Conclusions. The first detection of CO lines has provided a new way to investigate water fountain stars. Given the high expansion velocity of the CO gas and its relation to maser velocities, we infer that the CO emission region is co-located with the OH mainline masers in the warm base of the optical bipolar lobes, while the high velocity OH 1612 MHz and H(2)O masers are located in the side walls and at the farthest ends of the bipolar lobes, respectively. Further observations are highly desirable to understand the very low (12)CO/(13)CO line ratio.
学科主题	Astronomy & Astrophysics
WOS标题词	Science & Technology ; Physical Sciences
类目[WOS]	Astronomy & Astrophysics
研究领域[WOS]	Astronomy & Astrophysics
关键词[WOS]	GIANT BRANCH STARS ; BIPOLAR PROTOPLANETARY NEBULA ; PLANETARY-NEBULAE ; OH/IR STARS ; MASS-LOSS ; PREPLANETARY NEBULA ; CHEMICAL EVOLUTION ; IRAS 16342-3814 ; EVOLVED STARS ; CNO ISOTOPES
收录类别	SCI ; EI
原文出处	http://www.aanda.org/articles/aa/abs/2008/35/aa10303-08/aa10303-08.html
语种	英语
WOS记录号	WOS:000258760300003
内容类型	期刊论文
源URL	[http://ir.ynao.ac.cn/handle/114a53/4448]
专题	云南天文台_大样本恒星演化研究组
作者单位	1.Institute of Astronomy and Astrophysics, Academia Sinica, PO Box 23-141, Taipei 10617, Taiwan 2.National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, PO Box 110, Kunming, Yunnan Province 650011, PR China 3.Department of Physics, Faculty of Science, Kagoshima University, 1-21-35 Korimoto, Kagoshima 890-0065, Japan 4.Centre for Stellar and Planetary Astrophysics, School of Mathematical Sciences, Monash University, 3800 Melbourne, Australia 5.Department of Physics, University of Hong Kong, Pokfulam Road, Hong Kong
推荐引用方式 GB/T 7714	He JH,Imai, H,Hasegawa, TI,et al. First detection of CO lines in a water fountain star[J]. ASTRONOMY & ASTROPHYSICS,2008,488(2):L21-L24.
APA	He JH,Imai, H,Hasegawa, TI,Campbell, SW,&Nakashima, J.(2008).First detection of CO lines in a water fountain star.ASTRONOMY & ASTROPHYSICS,488(2),L21-L24.
MLA	He JH,et al."First detection of CO lines in a water fountain star".ASTRONOMY & ASTROPHYSICS 488.2(2008):L21-L24.