J/A+A/565/A127 SiO masers v=1,2,3 for 4 AGB (Desmurs+, 2014)
SiO masers in vibrationally excited v=1, v=2, and v=3 states.
Desmurs J.F., Bujarrabal V., Lindqvist M., Alcolea J., Soria-Ruiz R.,
Bergman P.
<Astron. Astrophys. 565, A127 (2014)>
=2014A&A...565A.127D 2014A&A...565A.127D
ADC_Keywords: Stars, late-type ; Stars, masers ; Interferometry ; Radio lines
Keywords: stars: AGB - circumstellar matter - masers - radio-lines: stars -
stars: individual: R Leo, IK Tau, TX Cam, U Her
Abstract:
The v=1 and 2 J=1-0 (43GHz), and v=1 J=2-1 (86GHz) SiO masers are
intense in AGB stars and have been mapped using VLBI showing ring-like
distributions. Those of the v=1, 2 J=1-0 masers are similar, but the
spots are rarely coincident, while the v=1 J=2-1 maser arises from a
well separated region farther out. These relative locations can be
explained by models including the overlap of two IR lines of SiO and
H2O. The v=3 J=1-0 line is not directly affected by any line overlap
and its spot structure and position, relative to the other lines, will
be a good test to the standard pumping models
The aims is to gain insight into the properties of the different SiO
masers and the general theoretical considerations that can help to
understand them.
We present single-dish and VLBI simultaneous observations of the v=1,
2, 3 J=1-0 maser transitions of 28SiO in several AGB stars. The
results are compared with the predictions of radiative models of SiO
masers both including and not including the effect of IR line overlap.
The spatial distribution of the SiO maser emission in the v=3 J=1-0
transition from AGB stars is systematically composed of a series of
spots occupying a ring-like structure (as often found in SiO masers).
The overall ring structure is extremely similar to that found in the
other 43 GHz transitions, and very different from the structure of the
v=1 J=2-1 maser. The positions of the individual spots of the
different 43 GHz lines are however very rarely coincident, being in
general separated by about 0.3AU (between 1 and 5mas). These results
are very difficult to reconcile with standard pumping models, which
predict the masers of rotational transitions within a given
vibrational state to require very similar excitation conditions (since
the levels are placed practically at the same energy from the ground),
while the transitions of different vibrational states (which are
separated by an energy of 1800K) should appear in different
positions. However, models including line overlap tend to predict
v=1, 2, 3 J=1-0 population inversion to occur under very similar
conditions, while the requirements for v=1 J=2-1 appears clearly
different, and are compatible with the observational results.
Description:
Summary of our three years monitoring with the Onsala telescope. For
each epoch (date format YYMMDD), we indicate the peak flux or, in case
of none detection, the upper limit. Values followed by asterix are the
closest observations in time to our VLBA observations.
Objects:
----------------------------------------------------------
RA (2000) DE Designation(s)
----------------------------------------------------------
09 47 33.49 +11 25 43.7 R Leo = V* R Leo
05 00 50.39 +56 10 52.6 TX Cam = V* TX Cam
16 25 47.47 +18 53 32.9 U Her = V* U Her
03 53 28.87 +11 24 21.7 IK Tau = V* IK Tau
----------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table3.dat 96 57 Monitoring flux intensity in lines v=1,2,3
sp/* . 614 Individual spectra
maps.dat 101 12 List of fits maps
maps/* . 12 Individual FITS maps
fig2/* . 7 Flux variation intensity v=1,2,3 individual
figures (in PNG)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Name Name of AGB star
12- 13 A2 --- Line Line (v1, v2 or v3)
15 A1 --- l_Fp1 Limit flag on Fp1
16- 19 F4.1 Jy Fp1 ?=- Peak flux observed on 2008/12/12
21 A1 --- l_Fp2 Limit flag on Fp2
22- 26 F5.2 Jy Fp2 ?=- Peak flux observed on 2009/03/17
28 A1 --- l_Fp3 Limit flag on Fp3
29- 33 F5.2 Jy Fp3 Peak flux observed on 2009/08/13
35 A1 --- l_Fp4 Limit flag on Fp4
36- 40 F5.2 Jy Fp4 Peak flux observed on 2009/11/07
41 A1 --- n_Fp4 [*] closest to VLBA observation (1)
42 A1 --- l_Fp5 Limit flag on Fp5
43- 47 F5.2 Jy Fp5 Peak flux observed on 2010/01/08
48 A1 --- n_Fp5 [*] closest to VLBA observation (1)
49 A1 --- l_Fp6 Limit flag on Fp6
50- 54 F5.2 Jy Fp6 Peak flux observed on 2010/12/06
56 A1 --- l_Fp7 Limit flag on Fp7
57- 61 F5.2 Jy Fp7 Peak flux observed on 2011/03/06
63 A1 --- l_Fp8 Limit flag on Fp8
64- 68 F5.2 Jy Fp8 Peak flux observed on 2011/04/22
69 A1 --- n_Fp8 [*] closest to VLBA observation (1)
70 A1 --- l_Fp9 Limit flag on Fp9
71- 75 F5.2 Jy Fp9 Peak flux observed on 2011/05/18
77 A1 --- l_Fp10 Limit flag on Fp10
78- 82 F5.2 Jy Fp10 Peak flux observed on 2011/06/15
84 A1 --- l_Fp11 Limit flag on Fp11
85- 89 F5.2 Jy Fp11 Peak flux observed on 2011/10/30
90 A1 --- n_Fp11 [*] closest to VLBA observation (1)
91 A1 --- l_Fp12 Limit flag on Fp12
92- 96 F5.2 Jy Fp12 Peak flux observed on 2011/12/09
--------------------------------------------------------------------------------
Note (1): Peak flux values mark with an asterix are the closest
observations in time to our VLBA observations.
--------------------------------------------------------------------------------
Byte-by-byte Description of file(!): sp/*
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
9- 12 I4 --- Chan Channel number
17- 32 F16.10 MHz RFreq Rest-frame frequency
38- 52 F15.12 Jy Tmb Brightness temperature
--------------------------------------------------------------------------------
Byte-by-byte Description of file: maps.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 25 F6.4 arcsec/pix Scale [0.0001] Scale of the image
27- 30 I4 --- Nx [1024] Number of pixels along X-axis
31 A1 --- --- [x]
32- 35 I4 --- Ny [1024] Number of pixels along Y-axis
37- 43 F7.4 GHz Freq [42.51/43.12] Frequency
49- 52 I4 Kibyte size [4129/4224] Size of FITS file
54- 66 A13 --- FileName Name of FITS file in subdirectory maps
68-101 A34 --- Title Title of the file
--------------------------------------------------------------------------------
Acknowledgements:
Jean-Francois Desmurs, desmurs(at)oan.es
(End) J.-F Desmurs [OAN, Spain], Patricia Vannier [CDS] 20-Mar-2014