J/ApJS/275/20 12yr KVN obs. of SiO and H2O masers toward WX Ser (Lim+, 2024)
Long-term simultaneous monitoring observations of SiO and H2O masers toward the
Mira variable WX Serpentis.
Lim J.-H., Kim J., Cho S.-H., Kim H., Yoon D.-H., Son S.-M., Suh K.-W.
<Astrophys. J. Suppl. Ser., 275, 20 (2024)>
=2024ApJS..275...20L 2024ApJS..275...20L
ADC_Keywords: Masers; Radio lines; Stars, giant; Stars, variable; Interferometry
Keywords: Silicon monoxide masers ; Water masers ;
Asymptotic giant branch stars ; Circumstellar envelopes ;
Time series analysis
Abstract:
We present the results from long-term simultaneous monitoring
observations of SiO and H2O masers toward the Mira variable star
WX Serpentis. This study has been conducted with 21m single-dish
radio telescopes of the Korean VLBI Network from 2009 June to
2021 June. Five maser lines were considered: SiO v=1,2, J=1-0;
SiO v=1, J=2-1, 3-2; and H2O 61,6-52,3 transitions, with the SiO
maser lines distributed near the stellar velocity and the H2O maser
exhibiting an asymmetric line profile with five to six peaked
components. Intense H2O maser emissions suddenly appeared in 2019
September, indicating flaring. The intensity variations of SiO and H2O
masers are strongly correlated with the optical light curve (OLC) of
the central star, with individual phase lags; the phase lag of the H2O
maser relative to the OLC is larger than that of the SiO masers. The
consequent phase difference between the SiO masers and the H2O maser
likely indicates that their formation regions and main driving
mechanisms are different from each other. The SiO masers in WX Ser
exhibit a dominant single-peak velocity distribution, similar to other
Mira variable stars. However, the H2O maser displays distinct
morphological features, showing a radial acceleration and preferential
intensity dominance at blueshifted velocities. This suggests that the
H2O maser clouds of WX Ser are moving outward, thereby developing an
asymmetric outflow owing to nonuniform material ejection from the
stellar atmosphere. The findings confirm that an initial asymmetric
outflow structure emerged during the thermally pulsing asymptotic
giant branch phase, specifically in the Mira variable star stage.
Description:
Over a 12yr period, i.e., from 2009 June to 2021 June, we carried out
simultaneous monitoring observations of SiO and H2O masers toward
WX Ser using three Korean VLBI Network (KVN) 21m single-dish
telescopes (KVN Yonsei, KVN Ulsan, and KVN Tamna). The observation
covered a broad frequency range, including 10 transitions of the SiO
and H2O isotopes.
We observed the H2O maser at 22.235GHz (K-band); 28SiO v=1, J=1-0 at
43.122GHz (Q-band); 28SiO v=2, J=1-0 at 42.820GHz throughout the
entire observation period (2009-2021); and 29SiO v=0, J=1-0 at
42.879GHz in seven epochs during 2009-2012. Since 2012, other lines
were included in our monitoring program, i.e., 28SiO v=1, J=2-1 at
86.243GHz (W-band) and 28SiO v=1, J=3-2 at 129.363GHz (D-band), as
well as two thermal lines; 28SiO v=0, J=1-0 and 2-1 lines; and
28SiO v=2, J=2-1 and 3-2 maser lines.
The monitoring observations were conducted at regular intervals of
2-5 months, except for two instances in which the observations were
performed over a duration of 1yr each.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
15 27 47.04 +19 33 51.6 WX Serpentis = V* WX Ser
----------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table3.dat 107 188 Observational results of SiO transitions
table4.dat 91 50 Observational results of the H2O maser line
table6.dat 45 52 Maser intensity ratios
table7.dat 68 50 Velocity extents of SiO and H2O maser lines
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See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
J/ApJS/165/360 : SiO maser emission toward 10 late-type stars (Kang+, 2006)
J/ApJ/669/446 : Observations of SiO masers (Nakashima+, 2007)
J/ApJS/190/203 : 3.6 years of DIRBE NIR stellar light curves (Price+, 2010)
J/AJ/144/129 : Properties of 83 known stellar SiO maser sources (Cho+, 2012)
J/AJ/145/22 : Simultaneous SiO and H2O maser observations (Kim+, 2013)
J/A+A/565/A127 : SiO masers v=1,2,3 for 4 AGB (Desmurs+, 2014)
J/AJ/147/22 : Simultaneous SiO and H2O maser observations. IV. (Kim+, 2014)
J/A+A/644/A45 : R Crt and RT Vir Medicina spectra (Brand+, 2020)
J/ApJS/253/44 : SiO maser emission in oxygen-rich stars (Rizzo+, 2021)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 17 A17 --- Maser Maser Line (G1)
19- 20 I2 --- Epoch [1/50] Epoch number
22- 31 A10 "Y/M/D" ObsDate Observation date (UT)
33- 37 F5.2 d Phase [0.18/10.6] Phase
39- 65 A27 Jy Speak Peak Flux density, Sν, list (1)
67- 72 F6.2 Jy.km.s-1 Snudnu [1.7/270.7]? Integral, Sν*dν
74- 78 F5.3 Jy rms [0.1/0.7]? Continuum root-mean-square noise
in observation
80-103 A24 km/s Vpeak Peak V, list (1)
105-107 F3.1 km.s-1 Vmean [3.8/9.1]? Mean maser velocity
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Note (1): Speak and Vpeak values are given as lists of detected
maser lines at that Epoch. The units of the Speak and Vpeak values are
Jy and km.s-1, respectively.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Epoch [1/50] Epoch number
4- 13 A10 "Y/M/D" ObsDate Observation date (UT)
15- 19 F5.2 d Phase [0.18/10.6] Phase
21- 24 F4.1 Jy Speak-B4 [0.8/44]? Peak Flux density, Blue-shifted
Line, 4
26- 28 F3.1 Jy Speak-B3 [0.7/4.5]? Peak Flux density,
Blue-shifted Line, 3
30- 34 F5.1 Jy Speak-B2 [0.8/121]? Peak Flux density,
Blue-shifted Line, 2
36- 39 F4.1 Jy Speak-B1 [0.7/26.4]? Peak Flux density,
Blue-shifted Line, 1
41- 44 F4.1 Jy Speak-R1 [1/29.3]? Peak Flux density, Red-shifted
Line, 1
46- 49 F4.1 Jy Speak-R2 [3/18.7]? Peak Flux density, Red-shifted
Line, 2
51- 55 F5.1 Jy.km.s-1 Snudnu [4/224.6] Integral, Sν*dν
57- 61 F5.3 Jy rms [0.1/0.5] Continuum root-mean-square
noise in observation
63- 66 F4.1 km.s-1 Vpeak-B4 [-3/-1.5]? Peak V, Blue-shifted Line, 4
68- 71 F4.1 km.s-1 Vpeak-B3 [-1.3/-0.3]? Peak V, Blue-shifted Line, 3
73- 75 F3.1 km.s-1 Vpeak-B2 [0.4/2.2]? Peak V, Blue-shifted Line, 2
77- 79 F3.1 km.s-1 Vpeak-B1 [2.5/4.7]? Peak V, Blue-shifted Line, 1
81- 83 F3.1 km.s-1 Vpeak-R1 [6.0/7.9]? Peak V, Red-shifted Line,1
85- 87 F3.1 km.s-1 Vpeak-R2 [8.3/9]? Peak V, Red-shifted Line,2
89- 91 F3.1 km.s-1 Vmean [0.3/7.7] Mean maser velocity
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Byte-by-byte Description of file: table6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- Epoch Epoch number (1)
6- 15 A10 "Y/M/D" ObsDate Observation date (UT)
17- 20 F4.2 --- Phase [0/1]? Optical Phase, normalized
22- 25 F4.2 --- Ratio1 [0.09/2.8] Maser Intensity Ratio,
I.F.(H2O)/I.F.(SiO43) (G1)
27- 30 F4.2 --- Ratio2 [0.27/2.2] Maser Intensity Ratio,
I.F.(SiO42)/I.F.(SiO43) (G1)
32- 35 F4.2 --- Ratio3 [0.18/1.51]? Maser Intensity Ratio,
I.F.(SiO86)/I.F.(SiO43) (G1)
37- 40 F4.2 --- Ratio4 [0.01/0.31]? Maser Intensity Ratio,
I.F.(SiO129)/I.F.(SiO43) (G1)
42- 45 F4.2 --- Ratio5 [0.02/0.5]? Maser Intensity Ratio,
I.F.(SiO129)/I.F.(SiO86) (G1)
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Note (1): The last two rows of this table provide the mean and standard
deviation of each column.
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Byte-by-byte Description of file: table7.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Epoch [1/50] Epoch number
4- 13 A10 "Y/M/D" ObsDate Observation date (UT)
15- 19 F5.2 d Phase [0.18/10.6] Phase
21- 24 F4.1 km.s-1 VB-SiO43 [-3.1/2.6] Blue velocity edge, SiO43 (G1)
26- 29 F4.1 km.s-1 VR-SiO43 [9.2/17.4] Red velocity edge, SiO43 (G1)
31- 34 F4.1 km.s-1 VB-SiO42 [-4.0/3.5] Blue velocity edge, SiO42 (G1)
36- 39 F4.1 km.s-1 VR-SiO42 [8.4/15.2] Red velocity edge, SiO42 (G1)
41- 44 F4.1 km.s-1 VB-SiO86 [-3.1/3.4]? Blue velocity edge, SiO86 (G1)
46- 49 F4.1 km.s-1 VR-SiO86 [10.9/15.6]? Red velocity edge, SiO86 (G1)
51- 53 F3.1 km.s-1 VB-SiO129 [0.3/5.1]? Blue velocity edge, SiO129 (G1)
55- 58 F4.1 km.s-1 VR-SiO129 [7.9/14.6]? Red velocity edge, SiO129 (G1)
60- 63 F4.1 km.s-1 VB-H2O [-8.7/2.4] Blue velocity edge, H2O (G1)
65- 68 F4.1 km.s-1 VR-H2O [9.2/16.6] Red velocity edge, H2O (G1)
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Global notes:
Note (G1):
SiO43 = 28SiO v=1, J=1-0 at 43.122GHz
SiO42 = 28SiO v=2, J=1-0 at 42.820GHz
SiO86 = 28SiO v=1, J=2-1 at 86.243GHz
SiO129 = 28SiO v=1, J=3-2 at 129.363GHz
H2O = H2O maser at 22.235GHz
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 20-Aug-2025