Detection of HC-13N maser emission from the ground state toward Y Canum Venaticorum

Izumiura, Hideyuki; Ukita, Nobuharu; Kawabe, Ryohei; Kaifu, Norio; Tsuji, Takashi; Unno, Wasaburo; Koyama, Kouichi

doi:10.1086/185062

Cited by 18 publications

(9 citation statements)

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“…Fortunately, in most cases this maser emission contributes to only a minor fraction of the total line intensity. Weak maser emission has been found in the HCN(J=l-0) line towards tenuous, C-rich CSEs Olofsson et al 1993b), and the same applies to the H 1 3 CN(J=l-0) line although here the statistics is poor (Izumiura et al 1987;Nyman et al 1993). The frequently observed SiO(J=2-1) line only occasionally shows evidence for weak maser features (Nyman & Olofsson 1985), while the less frequently observed SiO(J=l~0) line appears to be more affected by maser emission (Jewell et al 1991).…”

Section: T H E N a T U R E Of T H E C I R C U M S T E L L A R M O L Esupporting

confidence: 58%

Molecular Abundances in the Envelopes Around Evolved Stars

Olofsson

1994

International Astronomical Union Colloquium

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Red giant stars on the asymptotic giant branch (AGB), AGB-stars, lose copious amounts of matter in a slow stellar wind (Olofsson 1993). Mass loss rates in excess of 10-4M⊙yr-1have been measured. The primary observational consequence of this mass loss is the formation of an expanding envelope of gas and dust, a circumstellar envelope (CSE), that surrounds the star. This is a truly extended atmosphere that continues thousands of stellar radii away from the star. At the highest mass loss rates (which probably occur at the end of the AGB evolution) the CSE becomes so opaque that the photosphere is hidden and essentially all information about the object stems from the circumstellar emission. At some point on the AGB a star may change from being O-rich (i.e., the abundance of O is higher than that of C) to becoming C-rich (i.e., a carbon star where the abundance of C is higher than that of O) as a result of nuclear-processed material being dredged up to the surface. The chemical composition of the CSE will follow that of the central star, although with some time delay so that there may be some rare cases of O-rich CSEs around carbon stars. The mass loss decreases and changes its nature as the star leaves the AGB and starts its post-AGB evolution. Eventually the star becomes hot enough to ionize the inner part of the AGB-CSE and a planetary nebula (PN) is formed. The ultimate fate of the star is a long life as a slowly cooling white dwarf. The CSE will gradually disperse and its metal-enriched matter will mix with the interstellar medium, and thereby it contributes to the chemical evolution of a galaxy. The intense mass loss makes it possible for stars as massive as 8 M⊙, i.e., the bulk of all stars in a galaxy, to follow this evolutionary sequence. Similar CSEs are also found around supergiants.

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Section: T H E N a T U R E Of T H E C I R C U M S T E L L A R M O L Esupporting

confidence: 58%

Molecular Abundances in the Envelopes Around Evolved Stars

Olofsson

1994

International Astronomical Union Colloquium

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“…Evidence for weak maser action in the ground vi-J p 1-0 brational state line of HCN has been reported by Izumiura et al (1987), Izumiura, Ukita, & Tsuji (1995), and Olofsson et al (1993Olofsson et al ( , 1998 for a total of eight optically bright carbon stars. The observed lines show narrow, time-variable spikes superposed on a broad, constant profile.…”

Section: ϫ6mentioning

confidence: 77%

Discovery of Two New HCN Maser Lines in Five Carbon Stars

Bieging

2001

The Astrophysical Journal

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A survey with the Heinrich Hertz Submillimeter Telescope of HCN emission from mass-losing carbon stars has revealed masers in the and 4-3 transitions of the (01 0) vibrational bending mode. These lines 1c J p 3-2 have not previously been known to show maser action. Five stars-R Scl, V384 Per, R Lep, Y CVn, and V Cyg-out of 12 observed were detected as masers. Allowing for evidence of variability, this detection rate suggests that these HCN lines are masers at least some of the time in the majority of mass-losing carbon stars. The line widths and velocities imply that the maser action occurs in gas close to the star, where the circumstellar envelope is just being accelerated outward.

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“…Through a careful modelling, Schöier & Olofsson (2000) derive a circumstellar 13 CO/ 12 CO abundance ratio of 2.5. Y CVn has also been detected in the H 12 CN and H 13 CN (J = 1−0) ground state lines by Izumiura et al (1987). These emissions are time-variable, probably due to a maser effect, the latter having a peak-intensity of about half the former.…”

Section: Y Cvnmentioning

confidence: 93%

The circumstellar environments of EP Aqr and Y CVn probed by the H I emission at 21 cm

Bertre

Gérard

2004

A&A

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Abstract. The H I line at 21 cm has been detected in the circumstellar shells of the two semi-regular variables, EP Aqr and Y CVn, with the Nançay Radio-Telescope (NRT). In both cases the line shape is composite and the emission is spatially extended compared to the NRT beam size (4 ). The total H I masses of the two envelopes are respectively ∼0.047 M and 0.044 M . For EP Aqr, we find three components: a narrow one centered on the star and spatially unresolved, and two broad, Gaussian components, offset w.r.t. the star and spatially extended. The narrow component traces the present wind from EP Aqr whereas the two others seem to trace one or several mass-loss episodes of long duration. For Y CVn, we find two components: a narrow, spatially very extended, feature, and a broad one, less extended. We argue that the second component traces the outflow and the first one, its interaction with the ISM. These observations show that the H I emission can be used not only to probe the mass loss history of long-period variables, but also to investigate the interaction between stellar outflows and the surrounding ISM.

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Detection of HC-13N maser emission from the ground state toward Y Canum Venaticorum

Cited by 18 publications

References 0 publications

Molecular Abundances in the Envelopes Around Evolved Stars

Molecular Abundances in the Envelopes Around Evolved Stars

Discovery of Two New HCN Maser Lines in Five Carbon Stars

The circumstellar environments of EP Aqr and Y CVn probed by the H I emission at 21 cm

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