J/ApJ/741/94 VLBA observations of H20 maser in IRAS 18286-0959 (Yung+, 2011)
High velocity precessing jets from the water fountain IRAS 18286-0959 revealed
by Very Long Baseline Array observations.
Yung B.H.K., Nakashima J.-I., Imai H., Deguchi S., Diamond P.J., Kwok S.
<Astrophys. J., 741, 94 (2011)>
=2011ApJ...741...94Y 2011ApJ...741...94Y
ADC_Keywords: Masers ; Stars, giant ; Radio sources
Keywords: masers - stars: AGB and post-AGB - stars: evolution -
stars: winds, outflows
Abstract:
We report the results of multi-epoch Very Long Baseline Array
observations of the 22.2GHz H2O maser emission associated with the
"water fountain" IRAS 18286-0959. We suggest that this object is the
second example of a highly collimated bipolar precessing outflow
traced by H2O maser emission, the other is W 43A. The detected H2O
emission peaks are distributed over a velocity range from -50km/s to
150km/s. The spatial distribution of over 70% of the identified maser
features is found to be highly collimated along a spiral jet (jet 1)
extended southeast to northwest; the remaining features appear to
trace another spiral jet (jet 2) with a different orientation. The two
jets form a "double-helix" pattern which lies across ∼200mas. The
maser distribution is reasonably fit by a model consisting of two
bipolar precessing jets. The three-dimensional velocities of jet 1 and
jet 2 are derived to be 138km/s and 99km/s, respectively. The
precession period of jet 1 is about 56 years. For jet 2, three
possible models are tested and they give different values for the
kinematic parameters. We propose that the appearance of two jets is
the result of a single driving source with significant proper motion.
Description:
The VLBA observations of IRAS 18286-0959 were made at six epochs
(epochs A to F) over a year from 2008-Apr-21 to 2009-May-19.
Objects:
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RA (2000) DE Designation(s)
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18 31 22.91 -09 57 22.2 IRAS 18286-0959 = MSX6C G021.7964-00.1273
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 39 629 Parameters of the brightest H2O maser spot
from each detected maser feature in epoch A to F
(see Section 3 for details)
table3.dat 23 162 *Coordinates of 54 H2O maser features that appear
in any 3 consecutive epochs, selected from Table 2.
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Note on table3.dat: They are used for the proper motion calculation of
individual maser feature.
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See also:
J/MNRAS/416/1764 : H2O Southern Galactic Plane Survey (HOPS) (Walsh+, 2011)
J/ApJ/669/424 : H2O maser emissions of IRAS 19134+2131 (Imai+, 2007)
J/PASJ/59/1185 : Water maser in galactic IRAS sources (Sunada+, 2007)
J/A+A/434/201 : The 35um absorption line towards 1612MHz masers (He+, 2005)
J/A+A/366/481 : ATCA/VLA OH 1612 MHz survey. III. (Sevenster+, 2001)
J/MNRAS/276/57 : IRAS Galactic star-forming regions. II. (Codella+ 1995)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1 A1 --- Ep [A-F] Epoch between 2008-04-21 and 2009-05-19 (G1)
3- 8 F6.2 km/s VLSR Local Standard of Rest Velocity at intensity peak
10- 15 F6.2 mas oRA Right Ascension offset (G2)
17- 20 F4.2 mas e_oRA Uncertainty in oRA, from 2D Gaussian fitting
22- 28 F7.2 mas oDE Declination offset (G2)
30- 33 F4.2 mas e_oDE Uncertainty in oDE, from 2D Gaussian fitting
35- 39 F5.2 Jy Int H2O maser peak emission intensity; Jy/beam
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 mas oRA Right Ascension offset (G2)
11- 19 F9.4 mas oDE Declination offset (G2)
21 I1 --- Index [1/3] Epoch index (3)
23 A1 --- Ep [A-F] Epoch maser feature found in (G1)
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Note (3): The maser feature identified in the earliest epoch within their
own group is labelled as Index 1, and Index 3 is for the latest epoch.
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Global Notes:
Note (G1): Epoch as follows:
A = 2008 April 21;
B = 2008 May 29;
C = 2008 September 29;
D = 2008 November 28;
E = 2009 February 13;
F = 2009 May 19.
Note (G2): Position offset with respect to a selected maser feature
which appears in all the six epochs. This reference maser feature
(represented by its brightest maser spot) takes the coordinates (0,0)
in each epoch.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 25-Feb-2013