Polarisation observations of VY Canis Majoris H2O 532-441 620.701 GHz maser emission with HIFI

被引：15

作者：

Harwit, M. ^{[1
]}

Houde, M. ^{[2
]}

Sonnentrucker, P. ^{[3
]}

Boogert, A. C. A. ^{[4
]}

Cernicharo, J. ^{[5
]}

de Beck, E. ^{[6
]}

Decin, L. ^{[6
,16
]}

Henkel, C. ^{[7
]}

Higgins, R. D. ^{[8
]}

Jellema, W. ^{[9
]}

Kraus, A. ^{[7
]}

McCoey, C. ^{[2
,10
]}

Melnick, G. J. ^{[11
]}

Menten, K. M. ^{[7
]}

Risacher, C. ^{[9
]}

Teyssier, D. ^{[12
]}

Vaillancourt, J. E. ^{[13
]}

Alcolea, J. ^{[14
]}

Bujarrabal, V. ^{[15
]}

Dominik, C. ^{[16
,17
]}

Justtanont, K. ^{[18
]}

de Koter, A. ^{[16
,19
]}

Marston, A. P. ^{[12
]}

Olofsson, H. ^{[18
,20
]}

Planesas, P. ^{[15
,21
]}

Schmidt, M. ^{[22
]}

Schoier, F. L. ^{[18
]}

Szczerba, R. ^{[22
]}

Waters, L. B. F. M. ^{[6
,16
]}

机构：

[1] Cornell Univ, Ctr Radiophys & Space Res, Washington, DC 20024 USA

[2] Univ Western Ontario, Dept Phys & Astron, London, ON N6A 3K7, Canada

[3] Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA

[4] CALTECH, IPAC, Pasadena, CA 91925 USA

[5] CSIC, Madrid 28006, Spain

[6] Katholieke Univ Leuven, Inst Sterrenkundeii, B-3001 Heverlee, Belgium

[7] Max Planck Inst Radioastron, D-53121 Bonn, Germany

[8] Natl Univ Ireland, Dept Expt Phys, Maynooth, Kildare, Ireland

[9] Univ Groningen, SRON, NL-9700 AV Groningen, Netherlands

[10] Univ Waterloo, Dept Phys & Astron, Waterloo, ON N2L 3G1, Canada

[11] Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA

[12] European Space Astron Ctr, Madrid 28080, Spain

[13] NASA, SOFIA Sci Ctr, Univ Space Res Assoc, Ames Res Ctr, Moffett Field, CA 94035 USA

[14] Observ Astron Nacl IGN, Madrid 28014, Spain

[15] Observ Astron Nacl IGN, Alcala De Henares 28803, Spain

[16] Univ Amsterdam, Sterrenkundig Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands

[17] Radboud Univ Nijmegen, Dept Astrophys, IMAPP, NL-6525 ED Nijmegen, Netherlands

[18] Chalmers, Dept Radio & Space Sci, Onsala Space Observ, S-43992 Onsala, Sweden

[19] Univ Utrecht, Netherlands & Astron Inst, NL-3584 CC Utrecht, Netherlands

[20] Stockholm Univ, AlbaNova Univ Ctr, Dept Astron, S-10691 Stockholm, Sweden

[21] Joint ALMA Observ, Santiago, Chile

[22] Nicholas Copernicus Astron Ctr, PL-87100 Torun, Poland

来源：

ASTRONOMY & ASTROPHYSICS | 2010年 / 521卷

关键词：

stars: AGB and post-AGB; stars:; winds; outflows; supergiants; circumstellar matter; masers; reference systems; LATE-TYPE STARS; EVOLVED STARS; WATER MASERS; LINE; POLARIMETER; MILLIMETER; SHARP;

D O I：

10.1051/0004-6361/201015042

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

Context. Water vapour maser emission from evolved oxygen-rich stars remains poorly understood. Additional observations, including polarisation studies and simultaneous observation of different maser transitions may ultimately lead to greater insight. Aims. We have aimed to elucidate the nature and structure of the VY CMa water vapour masers in part by observationally testing a theoretical prediction of the relative strengths of the 620.701 GHz and the 22.235 GHz maser components of ortho H2O. Methods. In its high-resolution mode (HRS) the Herschel Heterodyne Instrument for the Far Infrared (HIFI) offers a frequency resolution of 0.125 MHz, corresponding to a line-of-sight velocity of 0.06 km s(-1), which we employed to obtain the strength and linear polarisation of maser spikes in the spectrum of VY CMa at 620.701 GHz. Simultaneous ground based observations of the 22.235 GHz maser with the Max-Planck-Institut fur Radioastronomie 100-m telescope at Effelsberg, provided a ratio of 620.701 GHz to 22.235 GHz emission. Results. We report the first astronomical detection to date of H2O maser emission at 620.701 GHz. In VY CMa both the 620.701 and the 22.235 GHz polarisation are weak. At 620.701 GHz the maser peaks are superposed on what appears to be a broad emission component, jointly ejected from the star. We observed the 620.701 GHz emission at two epochs 21 days apart, both to measure the potential direction of linearly polarised maser components and to obtain a measure of the longevity of these components. Although we do not detect significant polarisation levels in the core of the line, they rise up to approximately 6% in its wings.

引用

页数：5

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