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J/ApJ/805/53        H2O masers in W43A monitored with VLBA        (Chong+, 2015)

Water masers in W43A: early morphological changes of a future planetary nebula. Chong S.-N., Imai H., Diamond P.J. <Astrophys. J., 805, 53 (2015)> =2015ApJ...805...53C
ADC_Keywords: Masers ; Stars, giant ; Radio lines Keywords: circumstellar matter; masers; stars: AGB and post-AGB; stars: individual: W43A; stars: mass-loss; stars: winds, outflows 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 detected H2O maser features in W43A in 13 epochs across >10yr. 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. Description: The data belong to a comprehensive monitoring program of H2O masers (616-523, ν=22.235080GHz) in W43A, observed with the Very Long Baseline Array (VLBA) in 13 unequally spaced epochs in an extent of 10.8yr from 1994 June to 2005 April. Objects: ------------------------------------------------- RA (ICRS) DE Designation(s) ------------------------------------------------- 18 47 40.97 -01 44 55.4 W43A = OH 31.0 +0.0 ------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 46 525 Maser features detected in all thirteen epochs
See also: J/ApJS/211/15 : SiO & H2O maser survey toward AGB+post-AGB stars (Yoon+, 2014) J/ApJ/769/20 : 22GHz H2O maser survey toward IR sources (Yung+, 2013) J/A+A/546/A16 : 22-GHz water maser clouds (Richards+, 2012) J/ApJ/741/94 : VLBA obs. of H20 maser in IRAS 18286-0959 (Yung+, 2011) J/ApJ/669/424 : H2O maser emissions of IRAS 19134+2131 (Imai+, 2007) J/ApJ/658/1096 : H2O maser classification (Deacon+, 2007) J/PASJ/55/229 : SiO maser survey of cold IRAS sources (Nakashima+, 2003) J/A+AS/127/185 : SiO masers in OH/IR stars, proto-PN and PN (Nyman+ 1998) Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 2 I2 --- Epoch [1/13] Epoch number (1) 4- 10 F7.2 mas oRA [-377/455] Right Ascension offset (2) 12- 15 F4.2 mas e_oRA [0/0.6] Error in oRA (3) 17- 23 F7.2 mas oDE [-155/213] Declination offset (2) 25- 28 F4.2 mas e_oDE [0/0.5] Error in oDE (3) 30- 35 F6.2 km/s VLSR [-63/129] Local Standard of Rest velocity 37- 40 F4.2 km/s dV [0/8] Velocity width of feature ΔV (4) 42- 46 F5.2 Jy Int [0.04/53] Intensity; Jy/beam
Note (1): Epochs are defined in table 1 as follows: ------------------------------------------------------------ Ep Code Date JD tint Vref rms N -2400000 (min) (km/s) ------------------------------------------------------------ 1 BD03 1994-Jun-25 49528.8 273 123.9 18 24 2 BD17H 1994-Oct-11 49636.5 274 121.6 10 36 3 BD20 1995-Mar-17 49794.1 233 124.3 14 27 4 BI24B 2002-Apr-03 52368.1 223 119.3 6 52 5 BI24C 2002-Jul-26 52481.8 223 121.6 9 37 6 BI24F 2002-Nov-04 52583.4 222 122.7 7 38 7 BI27A 2003-Apr-03 52733.1 221 126.2 5 32 8 BI27B 2003-Aug-16 52867.7 224 125.6 8 50 9 BI27C 2003-Sep-06 52918.6 224 125.8 8 18 10 BI30A 2004-Aug-25 53242.9 198 125.8 8 94 11 BI30B 2004-Dec-04 53344.4 198 125.8 9 61 12 BI30C 2005-Feb-04 53406.1 165 126.0 4 21 13 BI30D 2005-Apr-06 53467.1 168 126.0 5 35 ------------------------------------------------------------ -- tint is the integration time. -- Vref is the LSR velocity channel used for phase referencing. -- rms is the rms noise in mJy/beam. -- N is the number of features. ------------------------------------------------------------ Note (2): Of the brightest point in the feature from the geometric center. Note (3): See Imai et al. (2002ApJ...567..971I) for the evaluation method. 0.00 means a value <0.005, for which only one spot is found in the feature, and observed with a very narrow beam aligned almost perpendicular to that direction. Note (4): The corresponding width of one channel is 0.11km/s.
History: From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 07-Sep-2015
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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