WATER MASERS IN W43A: EARLY MORPHOLOGICAL CHANGES OF A FUTURE PLANETARY NEBULA

ABSTRACT We present the distribution patterns of H2O maser features in the "water fountain" source (WF) W43A and show that they are closely related to the early morphological changes in a planetary nebula (PN). Using the Very Long Baseline Array, we have detected H2O maser features in W43A...

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Bibliographic Details
Published inThe Astrophysical journal Vol. 805; no. 1; pp. 1 - 9
Main Authors Chong, Sze-Ning, Imai, Hiroshi, Diamond, Philip J.
Format Journal Article
LanguageEnglish
Published United Kingdom The American Astronomical Society 20.05.2015
Subjects
Arrays
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
circumstellar matter
COMPARATIVE EVALUATIONS
DISTRIBUTION
Evolution
Holes
JET MODEL
MASERS
MASS TRANSFER
Mathematical morphology
PERIODICITY
PLANETARY NEBULAE
RED SHIFT
Similarity
STARS
stars: AGB and post-AGB
stars: individual (W43A)
stars: mass-loss
stars: winds, outflows
STELLAR WINDS
SYMMETRY
WATER
Water masers
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Summary:ABSTRACT We present the distribution patterns of H2O maser features in the "water fountain" source (WF) W43A and show that they are closely related to the early morphological changes in a planetary nebula (PN). Using the Very Long Baseline Array, we have detected H2O maser features in W43A in 13 epochs across yr. W43A is the only WF that has been observed for over a decade. We introduce a new cavity model scenario-a halo with a bipolar evacuated volume that has a partially enhanced wall-and compare it with the "traditional" precessing jet model particularly in terms of explaining the bow-shaped distribution patterns of H2O maser features in the most recent epochs and their temporal evolution. Long-term observations show that the distribution patterns require more than a single jet to form. Moreover, we have identified six groups of H2O maser features at both the redshifted and blueshifted sides with point symmetry. The six groups are believed to correspond to periodic mass profiles in the envelope and have recorded the mass-loss history. Together with a geometric similarity to the mid-infrared morphology of W43A, the results suggest that H2O masers can be used to trace the inner morphology and rapid temporal changes in evolved stars, especially where the PN shaping has just started.
Bibliography:Stars
ApJ93326
ObjectType-Article-1
SourceType-Scholarly Journals-1
ObjectType-Feature-2
content type line 23
ISSN:0004-637X
1538-4357
1538-4357
DOI:10.1088/0004-637X/805/1/53