Circumstellar Chemistry: The Effects of High Density Shells on the Distribution of Molecules in IRC+10216 Joanna Brown.

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Presentation transcript:

Circumstellar Chemistry: The Effects of High Density Shells on the Distribution of Molecules in IRC Joanna Brown

CW Leo: IRC Part of Asymptotic Giant Branch

Why is CW Leo chemically interesting? During helium flashes, convection zones form which bring C & O from the core to the surface. The C & O is then pushed outwards in the star’s wind

Rings around CW Leo From Mauron & Huggins (1999). Astron. Astrophys. 349, 204.

How does the model work? UV light Abundances of molecules Experimental and theoretical rates of reaction Differential rate equations Parent abundances

Effects of density rings on distribution No enhanced density shells Density enhancement of 6 times normal 1/r 2 distribution With shells at positions in agreement with observations Mass loss of 3.0E-5 M  /yr

Observational agreement From Guélin et al. (2000). IAU Symposium, 197, 369. Actual distribution in IRC using 3mm lines

Conclusions Density shells have a significant effect on chemical abundances and need included in the models Peak abundances are aligned in agreement with observations High abundance range is narrower than previous models in agreement with observations

Acknowledgments Dr. Tom Millar for providing such an interesting project and supervising my research Dr. David Cohen for advising on my thesis and this presentation My family for their support

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