1/15Multi-transition VLBA observations of circumstellar SiO masers. Soria-Ruiz et al.

Multi-transition VLBA observationsMulti-transition VLBA observationsof circumstellar SiO masersof circumstellar SiO masers

Rebeca Soria-Ruiz (Observatorio Astronómico Nacional, Spain)

r.soria@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)

2/15Multi-transition VLBA observations of circumstellar SiO masers. Soria-Ruiz et al.

SiO observational data SiO observational data

(1) Mass loss values taken from Loup et al. , 1993, A&AS 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

3/15Multi-transition VLBA observations of circumstellar SiO masers. Soria-Ruiz et al.

IRC +10011: 28SiO v =1 J = 1 0 (43 GHz)

4/15Multi-transition VLBA observations of circumstellar SiO masers. Soria-Ruiz et al.

IRC +10011: 28SiO v =2 J =1 0

5/15Multi-transition VLBA observations of circumstellar SiO masers. Soria-Ruiz et al.

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)

6/15Multi-transition VLBA observations of circumstellar SiO masers. Soria-Ruiz et al.

IRC +10011: 28SiO v =1 J = 2 1 (86 GHz)

7/15Multi-transition VLBA observations of circumstellar SiO masers. Soria-Ruiz et al.

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)

8/15Multi-transition VLBA observations of circumstellar SiO masers. Soria-Ruiz et al.

chi Cyg: 28SiO v =1 J =1 0 ( 43 GHz)

9/15Multi-transition VLBA observations of circumstellar SiO masers. Soria-Ruiz et al.

chi Cyg: 28SiO v =1 J = 2 1 (86 GHz)

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chi Cyg: 7 mm vs. 3 mm (v = 1)

Spatial distribution different in both transitions: only one possible “coincident” spot ?

Ring-like structure sizes: 7 mm: d 45 - 47 m.a.s.

3 mm: d 45 m.a.s.

Different flux-velocity distribution The emission arises in nearby (but not the same) projected regions.

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TX Cam: 28SiO v =1 J = 1 0 (43 GHz)

12/15Multi-transition VLBA observations of circumstellar SiO masers. Soria-Ruiz et al.

TX Cam: 28SiO v =2 J = 1 0

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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.

14/15Multi-transition VLBA observations of circumstellar SiO masers. Soria-Ruiz et al.

Conclusions

Source Comparison

* Results consistent with Desmurs J.F., et al. A&A, 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.

15/15Multi-transition VLBA observations of circumstellar SiO masers. Soria-Ruiz et al.

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 )