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Joanna Brown

Circumstellar Chemistry: The Effects of High Density Shells on the Distribution of Molecules in IRC+10216. Joanna Brown. CW Leo: IRC+10216. Part of Asymptotic Giant Branch. Why is CW Leo chemically interesting?.

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Joanna Brown

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

  2. CW Leo: IRC+10216 Part of Asymptotic Giant Branch

  3. 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

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

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

  6. Effects of density rings on distribution Density enhancement of 6 times normal 1/r2 distribution With shells at positions in agreement with observations No enhanced density shells Mass loss of 3.0E-5 M/yr

  7. Observational agreement Actual distribution in IRC+10216 using 3mm lines From Guélin et al. (2000). IAU Symposium, 197, 369.

  8. 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

  9. 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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