VLBI aperture synthesis observations of H2O masers associated with molecular clouds

Walker, R. C.; Burke, B. F.; Haschick, A. D.; Crane, P. C.; Moran, J. M.; Johnston, K. J.; Lo, K. Y.; Yen, J. L.; Broten, N. W.; Legg, T. H.; Greisen, E. W.; Hansen, S. S.

doi:10.1086/156589

Cited by 7 publications

(5 citation statements)

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“…This statement is in a good agreement with the results of VLBI observations (Walker et al 1978). If the envelope rotates and/or expands the spectral groups will be far one from another as far as the radial velocities.…”

Section: Discussionsupporting

confidence: 91%

“…For an assumed distance of 5.5 kpc the regions are each of about 1015 cm in size and are separated by about 2.7 1015 cm. The separation of the features is suggestive of a shell (Walker et al 1978).…”

Section: Introductionmentioning

confidence: 90%

“…VLBI aperture synthesis observations of H20 maser emission has been carried out by Walker et al (1978). The synthesis map of ON2 shows two regions of H20 emission.…”

Section: Introductionmentioning

confidence: 99%

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Time variations of the ON2 water maser spectrum during 1981-1995

Lekht

Márquez

Mendoza-Torres

1996

Astron. Astrophys. Suppl. Ser.

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Abstract. -Results of observations at 22.2 GHz of the water maser source ON2 carried out at the Pushchino RT-22 radio telescope during 1981-1995 are presented. The long-time regular observations of ON2 show that the time interval between the two high levels of the integrated H2O flux density is more than 20 years. The flare component of the variability of total flux as well as strong flares of some features were not detected. The emission is concentrated, basically, in two spectrally separated groups of features. The observed anticorrelation of the fluxes of these groups was manifested only in the period of minimum activity of the H2O maser. It seems that the transition of the maser takes place from the unsaturated state to a partly saturated one and vice versa. The variability of the maser emission has a global character for ON2 and may be caused by non-stationary physical processes at the early stages of stellar evolution.

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Section: Discussionsupporting

confidence: 91%

Section: Introductionmentioning

confidence: 90%

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Time variations of the ON2 water maser spectrum during 1981-1995

Lekht

Márquez

Mendoza-Torres

1996

Astron. Astrophys. Suppl. Ser.

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“…For a long time in VLBI, this technique was used only to measure relative fringe rates to high accuracy. Full advantage of the technique was taken for water masers by Walker et al (1978), and for OH masers by Reid et al (1980). Although maser clusters have the advantage of providing reference features within < 1", there are certain difficulties caused by the difference in frequency between the reference and referenced features that limit the ultimate accuracy of the technique (see Thompson, Moran, & Swenson 1986).…”

Section: Spectral Phase Referencingmentioning

confidence: 99%

Thirty Years of VLBI: Early Days, Successes, and Future

Moran

1998

International Astronomical Union Colloquium

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“…The main H 2 O maser source in ON2 (the northern one) is located near a compact HII region (Matthews et al 1973;Harris 1976;Matthews & Spoelstra 1983) and consists of two spatially separated regions, which are located on the opposite sides of a shell (Walker et al 1978) whose diameter is about 2.7 10 15 cm. According to recent VLBI observations, the main H 2 O maser is composed of three groups of features, located in a volume with diameter about 4 10 16 cm (Hofner & Churchwell 1996).…”

Section: Introductionmentioning

confidence: 99%

Variation of spectral features in the ON2 water maser

Márquez

Mendoza-Torres

Lekht

1998

Astron. Astrophys. Suppl. Ser.

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Abstract. Results are presented of the analysis of H 2 O maser spectra in ON2, obtained with the RT-22 radio telescope at Pushchino during 1981-1996. The spectral features are analyzed and their time evolution examined. Anticorrelation between the fluxes of features with close radial velocities is found. A systematic displacement of the drifts sum of all features from 0.8 to −0.3 km s −1 year −1 during 1981-1988 and 1990-1996 is observed. In 1989 a fast jump of this parameter from −0.3 to 0.8 km s −1 year −1 took place. The quadratic sum of the drifts of the features always increased during a rise in maser activity. Possible causes of the observed phenomena are discussed.

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VLBI aperture synthesis observations of H2O masers associated with molecular clouds

Cited by 7 publications

References 0 publications

Time variations of the ON2 water maser spectrum during 1981-1995

Time variations of the ON2 water maser spectrum during 1981-1995

Thirty Years of VLBI: Early Days, Successes, and Future

Variation of spectral features in the ON2 water maser

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