SiO masers in OH/IR stars, proto–planetary and planetary
nebulae

Nyman, L.-Å.; Hall, Peter; Olofsson, H.

doi:10.1051/aas:1998343

Cited by 75 publications

(81 citation statements)

References 22 publications

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“…The spectra commonly show a broad peak that is 5Y15 km s À1 wide and centered on the stellar velocity (Nyman et al 1998). The emission is highly variable, with lifetimes for individual clumps of no more than a few months seen in both spectral and high-resolution observations (Elitzur 1992;Humphreys 2002).…”

Section: Sio Maser Emission In Evolved Starsmentioning

confidence: 99%

H₂O Maser Observations of Candidate Post‐AGB Stars and Discovery of Three High‐Velocity Water Sources

Deacon

Chapman

Green

et al. 2007

ApJ

106

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We present the results of 22 GHz H 2 O maser observations of a sample of 85 postYasymptotic giant branch ( post-AGB) candidate stars, selected on the basis of their OH 1612 MHz maser and far-infrared properties. All sources were observed with the Tidbinbilla 70 m radio telescope, and 21 detections were made; 86 GHz SiO Mopra observations of a subset of the sample are also presented. Of the 21 H 2 O detections, 15 are from sources that are likely to be massive AGB stars and most of these show typical, regular H 2 O maser profiles. In contrast, nearly all the detections of more evolved stars exhibited high-velocity H 2 O maser emission. Of the five sources seen, v223 (W43A, IRAS 18450À0148) is a well-known ''water-fountain'' source that belongs to a small group of post-AGB stars with highly collimated, high-velocity H 2 O maser emission. A second source in our sample, v270 (IRAS 18596+0315), is also known to have high-velocity emission. We report the discovery of similar emission from a further three sources, d46 (IRAS 15445À5449), d62 (IRAS 15544À5332), and b292 (IRAS 18043À2116). The source d46 is an evolved post-AGB star with highly unusual maser properties. The H 2 O maser emission from d62 is probably associated with a massive star. The source b292 is a young post-AGB star that is highly likely to be a water-fountain source, with masers detected over a velocity range of 210 km s À1 .

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Section: Sio Maser Emission In Evolved Starsmentioning

confidence: 99%

H₂O Maser Observations of Candidate Post‐AGB Stars and Discovery of Three High‐Velocity Water Sources

Deacon

Chapman

Green

et al. 2007

ApJ

106

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“…IRAS 19114+0002 has been classified as either a PPN descended from low-or intermediate-mass progenitor (Reddy & Hrivnak 1999) or a yellow hypergiant (YHG) descended from a massive ($30 M ) Population I supergiant (e.g., Jura & Werner 1999;Castro-Carrizo et al 2007). YHGs are believed to follow an evolutionary path similar to that of PPNs; they undergo a strong Klochkova et al 1999;(6) Klochkova et al 2002;(7) Loup et al 1993;(8) Lowe & Gledhill 2007;(9) Mauron & Huggins 2006;(10) Nyman et al 1998;(11) Oppenheimer & Davé 2006;(12) Reddy & Hrivnak 1999;(13) Sahai et al 2003;(14) Sahai et al 2005;(15) Sahai et al 2007a;(16) Sahai et al 2008;(17) R. Sahai et al in preparation ( HST GO 9463, 10185);(18) Sánchez Contreras et al 2006a, 2006b(19) Schmidt et al 2002;(20) Sevenster 2002;(21) Su et al 2001;(22) Suárez et al 2006;(23) Szczerba et al 2007: The Torun Catalogue of Galactic Post-AGB and Related Objects; (24) Ueta et al 2000;(25) Ueta et al 2007;(26) van der Veen et al 1989;(27) Začs et al 1996. mass-loss process leading to massive CSEs...…”

Section: The Samplementioning

confidence: 99%

Echelle Long‐Slit Optical Spectroscopy of Evolved Stars

Contreras

Sahai²,

Paz

et al. 2008

Astrophysical Journal Supplement Series, The

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We present echelle long-slit optical spectra of a sample of objects evolving off the asymptotic giant branch (AGB), most of them in the preplanetary nebula ( PPN ) phase, obtained with the ESI and MIKE spectrographs at the 10 m Keck II and 6.5 m Magellan-I telescopes, respectively. The total wavelength range covered with ESI (MIKE) is $3900Y10900 8 ($3600Y7200 8). In this paper, we focus our analysis mainly on the H profiles. Prominent H emission is detected in half of the objects, most of which show broad H wings (with total widths of up to $4000 km s À1 ). In the majority of the H -emission sources, fast, post-AGB winds are revealed by P-Cygni profiles. In $37% of the objects H is observed in absorption. In almost all cases, the absorption profile is partially filled with emission, leading to complex, structured profiles that are interpreted as an indication of incipient post-AGB mass loss. The rest of the objects ($13%) are H nondetections. We investigate correlations between the H profile and different stellar and envelope parameters. All sources in which H is seen mainly in absorption have F-G type central stars, whereas sources with intense H emission span a larger range of spectral types from O to G, with a relative maximum around B, and also including very late C types. Shocks may be an important excitation/ionization agent of the close stellar surroundings for objects with late type central stars. Sources with pure emission or P Cygni H profiles have larger J À K color excess than objects with H mainly in absorption, which suggests the presence of warm dust near the star in the former. The two classes of profile sources also segregate in the IRAS color-color diagram in a way that intense H -emitters have dust grains with a larger range of temperatures. Spectral classification of the central stars in our sample is presented. For a subsample (13 objects), the stellar luminosity has been derived from the analysis of the O i 7771Y7775 8 infrared triplet. The location in the HR diagram of most of these targets, which represent $30% of the whole sample, is consistent with relatively high final (and, presumably, initial) masses in the range M f $ 0:6 Y0:9 M (M i $ 3Y 8 M ).

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“…Disappearance of H 2 O maser emission (Engels 2002) and non-detection of SiO maser emission (Nyman et al 1998) indicate its post-AGB nature. This is consistent with its bimodal infrared energy distribution similar to that observed in young planetary nebulae (Le Bertre 1987).…”

Section: Introductionmentioning

confidence: 99%

Burst of strongly polarized maser emission at 1612 MHz in the proto-planetary nebula OH17.7–2.0

Szymczak¹,

Gérard²

2005

A&A

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Abstract.We report the discovery of a burst of highly polarized OH maser emission at 1612 MHz in the proto-planetary nebula candidate OH17.7−2.0. The total flux density of two red-shifted features at 72.8 and 73.3 km s −1 increased nearly threefold over a period of ∼430 days. This burst was not associated with any systematic changes of the other 1612 MHz maser features as well as of the 1665 and 1667 MHz masers. The burst was characterized by a linear growth of left-hand circularly polarized emission accompanied by considerable linearly polarized emission. During the burst, the degrees of circular and linear polarization increased up to −80% and 15% respectively. A relation found between the line width and the peak flux density of the two bursting features implies a saturated amplification. Among several possible causes of the burst, a local propagation effect due to Zeeman overlap initiated by evolutionary changes in the shell appears most plausible.

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SiO masers in OH/IR stars, proto–planetary and planetary nebulae

Cited by 75 publications

References 22 publications

H₂O Maser Observations of Candidate Post‐AGB Stars and Discovery of Three High‐Velocity Water Sources

H₂O Maser Observations of Candidate Post‐AGB Stars and Discovery of Three High‐Velocity Water Sources

Echelle Long‐Slit Optical Spectroscopy of Evolved Stars

Burst of strongly polarized maser emission at 1612 MHz in the proto-planetary nebula OH17.7–2.0

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SiO masers in OH/IR stars, proto–planetary and planetary nebulae

Cited by 75 publications

References 22 publications

H2O Maser Observations of Candidate Post‐AGB Stars and Discovery of Three High‐Velocity Water Sources

H2O Maser Observations of Candidate Post‐AGB Stars and Discovery of Three High‐Velocity Water Sources

Echelle Long‐Slit Optical Spectroscopy of Evolved Stars

Burst of strongly polarized maser emission at 1612 MHz in the proto-planetary nebula OH17.7–2.0

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H₂O Maser Observations of Candidate Post‐AGB Stars and Discovery of Three High‐Velocity Water Sources

H₂O Maser Observations of Candidate Post‐AGB Stars and Discovery of Three High‐Velocity Water Sources