SiO masers

1
Multi-transition VLBA observations of
circumstellar SiO masers
Rebeca Soria-Ruiz (Observatorio Astronómico
Nacional, Spain) r.soria_at_oan.es
Francisco Colomer (OAN) Javier Alcolea
(OAN) Valentín Bujarrabal (OAN) Jean-Francois
Desmurs (OAN)
K. B. Marvel (AAS) D. Boboltz (USNO) P. J.
Diamond (JBO) A. J. Kemball (NRAO)
2
SiO observational data
(1) Mass loss values taken from Loup et al. ,
1993, AAS 99, 291 (2) Phase with respect to
the NIR/SiO maximum extrapolated from Pardo J.R.,
Alcolea J. Bujarrabal V. (in prep.) (3)
Phases with respect to the optical maximum
derived from the light curves available at
http//www.aavso.org/lightcurves
3
IRC 10011 28SiO v 1 J 1 0 (43 GHz)
4
IRC 10011 28SiO v 2 J 1 0
5
IRC 10011 v 1 vs. v 2 (J 1 0)
? Similar spatial distribution ?
Ring-like structure sizes v 1 d ? 20
m.a.s. v 2 d ? 18 m.a.s. ? Consistent
with Desmurs et al. (2000)
6
IRC 10011 28SiO v 1 J 2 1 (86 GHz)
7
IRC 10011 7 mm vs. 3 mm (v 1)
? Spatial distribution quite different
in both transitions and non-coincident. ?
Ring-like structure sizes 7 mm d ? 20
m.a.s. 3 mm d ? 25-30 m.a.s.
Contradiction with the current SiO masers pumping
mechamisms
?
c f. similar study of R Cas by Phillips et al.
(2003)
8
chi Cyg 28SiO v 1 J 1 0 ( 43 GHz)
9
chi Cyg 28SiO v 1 J 2 1 (86 GHz)
10
chi Cyg 7 mm vs. 3 mm (v 1)
? Spatial distribution different in both
transitions only one possible
coincident spot ?
Different flux-velocity distribution The
emission arises in nearby (but not the same)
projected regions.
? Ring-like structure sizes 7 mm
d ? 45 - 47 m.a.s. 3 mm d ? 45 m.a.s.
11
TX Cam 28SiO v 1 J 1 0 (43 GHz)
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TX Cam 28SiO v 2 J 1 0
13
TX Cam v 1 vs. v 2 (J 1 0)
? Similar spatial distribution in both
transitions. ? Ring-like structure sizes v
1 d ? 28 m.a.s. v 2 d ? 26
m.a.s.
14
Conclusions
Source Comparison
Results consistent with Desmurs J.F., et al.
AA, 360 , 189 (2000)
Observational results clearly contradict the
theoretical models, where the spatial
distributions and ring structure sizes of the
J 1-0 and J 2-1 (v 1) transitions should
be similar.
?
15
Work in progress
?

• We are investigating the prevalence of these
  results, on a second epoch already observed (both
  at 7mm and 3mm) on these sources and R Leo, as
  well as the detailed study of the possible
  effects on the pumping mechanism as a function
  of
• Phase of the stellar pulsation
• Mass loss rate
• Chemical properties (in particular, line
  overlaps between ro-vibrational SiO and H2O
  transitions )