H<sub>2</sub>O maser emission of the M-type supergiant VX Sgr

Berulis, I. I.; Pashchenko, M. I.; Rudnitskij, G. M.

doi:10.1080/10556799908203038

Cited by 7 publications

(8 citation statements)

References 6 publications

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“…However, during the next 3 periods the amplitude fell to ∼1 mag, and the 1999 22‐GHz data were observed very close to a weaker 9.1‐mag maximum following a period of only about half the usual 732 d. Years of very weak optical periods have been seen before, most recently in 1962–64 (Mattei 1993; Mayall 1970). Pashchenko & Rudnitskii (1999) and Berulis, Pashchenko & Rudnitskij (1999) suggest there is a relationship between the stellar optical and the H 2 O maser variability, caused by shocks propagating out from the photosphere that take decades to reach and cross the H 2 O maser region. However we see the whole shell changing in flux density over a few years.…”

Section: The Structure and Evolution Of The Maser Shellmentioning

confidence: 99%

The radially expanding molecular outflow of VX Sagittarii

Murakawa

Yates

Richards

et al. 2003

Monthly Notices of the Royal Astronomical Society

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We used MERLIN to observe 22‐GHz H2O maser emission from the red supergiant VX Sgr in 1994 and 1999. The masers lie in a region 300–400 mas in diameter. The angular size and the velocity distribution of the masers are similar at both epochs, although the total flux density in 1999 is only half of that seen in 1994. The maser emission is resolved into clouds of average diameter (11.5 ± 4.0) mas which we infer are ∼300 times denser than the surrounding wind. The cloud radius is comparable to the stellar radius. We have previously found an order of magnitude variation in the size of H2O clouds around other evolved stars of masses 1–20 M⊙, but the average size is consistently proportional to stellar size. 43 out of 92 distinct maser clouds observed in 1994 were matched with clouds seen in 1999. The mean change in position is 10.7 mas. The radial component of proper motion is directed away from the centre of expansion and increases with increasing angular separation. There is no significant rotational proper motion. The expansion proper motions are consistent with the maser Doppler velocities if VX Sgr is at (1.8 ± 0.5) kpc. The maser distribution and kinematics suggest a spheroidal thick shell in which the stellar wind is undergoing radial acceleration, from 10 km s−1 at the inner edge of the maser shell to 20 km s−1 at the outer edge. We suggest a model for the asymmetric appearance of the maser shell and compare this with the magnetic field direction deduced from OH 1612‐MHz maser observations. The maser expansion velocities have doubled between 1983 and 1994, suggesting the entire H2O maser shell has become more effectively accelerated, on a time‐scale much longer than the light‐crossing time for the maser shell and much shorter than the wind‐crossing time.

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Section: The Structure and Evolution Of The Maser Shellmentioning

confidence: 99%

The radially expanding molecular outflow of VX Sagittarii

Murakawa

Yates

Richards

et al. 2003

Monthly Notices of the Royal Astronomical Society

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“…In the past S Per also had intervals of strong light variations (1919)(1920)(1921)(1922)(1923)(1924)(1925)(1926)(1927), followed by ones of smaller amplitude (1927)(1928)(1929)(1930)(1931)(1932)(1933)(1934)(1935)(1936)(1937)(1938), and then again stronger changes, though at a lower mean level (see Bidelman 1947, and references therein), just like the curve for 1990-2002. In many respects the visual curve of S Per resembles that of VX Sgr, also with alternating large-and smallamplitude variations (Dinerstein 1973;Berulis et al 1999).…”

Section: Introductionmentioning

confidence: 99%

Variability of the H₂O maser associated with the M-supergiant S Persei

Lekht

Rudnitskij²,

Mendoza-Torres

et al. 2005

A&A

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Abstract. We present the results from observing the circumstellar maser emission of the M-type supergiant S Per in the 6 16 -5 23 water-vapour line at 1.35 cm. The observations were carried out in 1981-2002 (JD = 2 444 900-2 452 480) on the RT-22 radio telescope of the Pushchino Radio Astronomy Observatory, Astrospace Center of the Lebedev Institute of Physics, Russian Academy of Sciences. The H 2 O spectra obtained represent an unprecedented long, uniform dataset on this star. We discuss the properties of the optical and maser variations of S Per, together with particulars of the available VLBI maps. The close relation between maser and optical variations favors a model in which mass-loss is episodic. Changes observed in the total H 2 O line flux follow the visual light curve with a delay of 0.01 to 0.5P, where P ≈ 800 d is the mean light cycle for S Per. The feature at V LSR = −44 km s −1 flared in July 1988, which seemed to be the response of the maser to an unusually bright optical maximum. The position of the −44-km s −1 feature on the VLBI maps coincides with the direction toward the optical stellar disc, which can be explained by amplification of enhanced stellar continuum by the H 2 O line.

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“…We have extensively observed this star since 1981. Some results were published in [4,5]. A sample profile of the H 2 O line in VX Sgr is given in figure 1.…”

Section: Vx Sagittariimentioning

confidence: 95%

“…In a bipolar outflow expanding at velocity V 0 , pairs of B features are formed with spacing 2 1 = 2V 0 cos i between pair centres and spacing 2 = 2V 0 sin ϑ sin i between the features in each pair ( figure 2(b)). Estimates in [4] show that that the opening angle ϑ of the bipolar outflow of VX Sgr is about 60 • , and the angle of inclination i of the outflow axis to the line of sight is also 60 • . Another source, IRC-0414, has quite a similar H 2 O line profile to that of VX Sgr.…”

Section: Vx Sagittariimentioning

confidence: 98%

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Water masers in red supergiants

Pashchenko

Rudnitskij

Самодуров

et al. 2006

Astronomical & Astrophysical Transactions

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Results of long-term monitoring of circumstellar water maser sources in red supergiants are reviewed.The observations were carried out in 1980-2006 on the RT-22 radio telescope at Pushchino Radio Astronomy Observatory. We discuss the results for the semiregular variable M-supergiant VX Sgr and non-variable M-supergiant IRC-10414. In addition to our single-dish data, very-long-baseline interferometry results are invoked. VX Sgr and IRC-10414 display a characteristic water line profile, which suggests the presence of a rotating circumstellar disc and a bipolar outflow.

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H₂O maser emission of the M-type supergiant VX Sgr

Cited by 7 publications

References 6 publications

The radially expanding molecular outflow of VX Sagittarii

The radially expanding molecular outflow of VX Sagittarii

Variability of the H₂O maser associated with the M-supergiant S Persei

Water masers in red supergiants

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H2O maser emission of the M-type supergiant VX Sgr

Cited by 7 publications

References 6 publications

The radially expanding molecular outflow of VX Sagittarii

The radially expanding molecular outflow of VX Sagittarii

Variability of the H2O maser associated with the M-supergiant S Persei

Water masers in red supergiants

Contact Info

Product

Resources

About

H₂O maser emission of the M-type supergiant VX Sgr

Variability of the H₂O maser associated with the M-supergiant S Persei