Observations of SiO maser sources at 43.122 GHz

Abstract. Recent hydrodynamical models (Winters et al. 2000b) allow the existence of pulsating, large velocity amplitude Asymptotic Giant Branch (AGB) stars with tenuous dusty circumstellar shells, which produce low mass-loss rates and simultaneously low wind velocities. The Semi-regular long-period variable L 2 Pup shows a broad SiO maser feature at 86 GHz (v = 1, J = 2−1), indicating an outward velocity of the material close to the stellar photosphere of at least 10 km s −1 , and narrow CO (J = 2−1) and (1−0) line profiles indicating an outflow velocity of the material in the circumstellar shell of only about 3 km s −1 . This can be explained in terms of our hydrodynamical models which provide large velocities in the shocked stellar atmosphere and low velocities of the circumstellar outflow.

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“…Lépine et al (1978) (Dickinson et al 1986), a result which was confirmed by Te Lintel Hekkert et al (1991).…”

mentioning

confidence: 52%

The hydrodynamical structure of circumstellar envelopes around low mass-loss rate, low outflow velocity AGB stars

Winters

Bertre

Nyman

et al. 2002

A&A

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“…The molecular emission of L 2 Pup has been extensively monitored in the past fifty years; it showed the variability of the outflow velocity (Kerschbaum et al 1996;Kerschbaum & Olofsson 1999;Winters et al 2002Winters et al , 2003Lepine et al 1976Lepine et al , 1978Haikala 1990;Haikala et al 1994;Menten & Melnick 1991;Gomez Balboa & Lepine 1986;Caswell et al 1971;Knowles & Batchelor 1978;Balister et al 1977;Schöier et al 2004;González Delgado et al 2003). González Delgado et al (2003) reported that the interior of the circumstellar envelope of L 2 Pup is probably complex, based on their SiO observations.…”

Section: Toroidal Structure Hypothesismentioning

confidence: 99%

Dissecting the AGB star L₂Puppis: a torus in the making

Lykou

Klotz

Paladini

et al. 2015

A&A

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Aims. The circumstellar environment of L 2 Pup, an oxygen-rich semiregular variable, was observed to understand the evolution of mass loss and the shaping of ejecta in the late stages of stellar evolution. Methods. High-angular resolution observations from a single 8 m telescope were obtained using aperture masking in the near-infrared (1.64, 2.30 and 3.74 μm) on the NACO/VLT, both in imaging and polarimetric modes. Results. The aperture-masking images of L 2 Pup at 2.30 μm show a resolved structure that resembles a toroidal structure with a major axis of ∼140 milliarcseconds (mas) and an east-west orientation. Two clumps can be seen on either side of the star, ∼65 mas from the star, beyond the edge of the circumstellar envelope (estimated diameter is ∼27 mas), while a faint, hook-like structure appear toward the northeast. The patterns are visible both in the imaging and polarimetric mode, although the latter was only used to measure the total intensity (Stokes I). The overall shape of the structure is similar at the 3.74 μm pseudo-continuum (dust emission), where the clumps appear to be embedded within a dark, dusty lane. The faint, hook-like patterns are also seen at this wavelength, extending northeast and southwest with the central, dark lane being an apparent axis of symmetry. We interpret the structure as a circumstellar torus with inner radius of 4.2 au. With a rotation velocity of 10 km s −1 as suggested by the SiO maser profile, we estimate a stellar mass of 0.7 M .

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“…The star RS Vir has been repeatedly studied in the 22-GHz H 2 O line by Baudry & Welch (1974), Lépine et al (1974Lépine et al ( , 1978, Hagen (1979), Crocker & Hagen (1983). Barvainis & Deguchi (1989), Comoretto et al (1990), Menten & Melnick (1991), Palagi et al (1993), Takaba et al (1994), Szymczak & Le Squeren (1999).…”

Section: Model Of Variability Of the Circumstellar H 2 O Maser Rs Virmentioning

confidence: 99%

Variability of the H₂O maser associated with the Mira variable RS Virginis

Lekht

Mendoza-Torres

Rudnitskij³

et al. 2001

A&A

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Abstract.The results of observations of the H2O maser emission (λ = 1.35 cm) of the Mira-type variable star RS Vir are presented. The observations were carried out in 1981-2001 (JD = 2 444 900−2 451 995) on the RT-22 radio telescope of the Pushchino Radio Astronomy Observatory (Russia). The variability curve of the H2O maser emission integrated flux Fint(H2O) of RS Vir correlates with its visual light curve with some phase delay ∆ϕ = (0.05−0.35)P (P is the star's period). The delay variations seem to be periodic at a timescale of 19-20 years ("superperiod" of the maser variations). If the variability of the H2O maser RS Vir is caused by periodic action of pulsation-driven shock waves, the shock travel time from the photosphere to the inner boundary of the H2O maser shell can be as long as (3-5)P . Another explanation is that maser variations may be connected with changing gas density in the masering region of the circumstellar envelope. In particular, long-term maser variations (the "superperiod") may be caused by changing mass loss rateṀ .

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Observations of SiO maser sources at 43.122 GHz

Cited by 40 publications

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The hydrodynamical structure of circumstellar envelopes around low mass-loss rate, low outflow velocity AGB stars

The hydrodynamical structure of circumstellar envelopes around low mass-loss rate, low outflow velocity AGB stars

Dissecting the AGB star L₂Puppis: a torus in the making

Variability of the H₂O maser associated with the Mira variable RS Virginis

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Observations of SiO maser sources at 43.122 GHz

Cited by 40 publications

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The hydrodynamical structure of circumstellar envelopes around low mass-loss rate, low outflow velocity AGB stars

The hydrodynamical structure of circumstellar envelopes around low mass-loss rate, low outflow velocity AGB stars

Dissecting the AGB star L2Puppis: a torus in the making

Variability of the H2O maser associated with the Mira variable RS Virginis

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Dissecting the AGB star L₂Puppis: a torus in the making

Variability of the H₂O maser associated with the Mira variable RS Virginis