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

M. Harwit ; M. Houde ; P. Sonnentrucker ; A. C. A. Boogert ; J. Cernicharo ; E. De Beck ; L. Decin ; C. Henkel ; R. D. Higgins ; W. Jellema ; A. Kraus ; C. McCoey ; G. J. Melnick ; K. M. Menten ; C. Risacher ; D. Teyssier ; J. E. Vaillancourt ; J. Alcolea ; V. Bujarrabal ; C. Dominik ; Kay Justtanont (Institutionen för rymd- och geovetenskap, Onsala rymdobservatorium) ; A. de Koter ; A. P. Marston ; Hans Olofsson (Institutionen för rymd- och geovetenskap, Onsala rymdobservatorium) ; P. Planesas ; M. Schmidt ; Fredrik L. Schöier (Institutionen för rymd- och geovetenskap, Onsala rymdobservatorium) ; R. Szczerba ; Lbfm Waters
Astronomy and Astrophysics (0004-6361). Vol. 521 (2010), p. Article Number: L51.
[Artikel, refereegranskad vetenskaplig]

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.

Nyckelord: 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



Denna post skapades 2010-12-28. Senast ändrad 2015-06-23.
CPL Pubid: 131897

 

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Institutioner (Chalmers)

Institutionen för rymd- och geovetenskap, Onsala rymdobservatorium (2010-2017)

Ämnesområden

Astronomi, astrofysik och kosmologi

Chalmers infrastruktur