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A Carbon Rich Mira Variable In a Globular Cluster: A Stellar Merger

A Carbon Rich Mira Variable In a Globular Cluster: A Stellar Merger MW Feast JW Menzies PA Whitelock SAAO and UCT Published online MNRAS Letters 29 Oct 2012. N Matsunga (Thesis: Tokyo) 2006 Intensive survey of globular clusters with the IRSF for variables Lynga 7 V1 Mira variable

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A Carbon Rich Mira Variable In a Globular Cluster: A Stellar Merger

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  1. A Carbon Rich Mira Variable In a Globular Cluster: A Stellar Merger MW Feast JW Menzies PA Whitelock SAAO and UCT Published online MNRAS Letters 29 Oct 2012

  2. N Matsunga (Thesis: Tokyo) 2006 Intensive survey of globular clusters with the IRSF for variables Lynga 7 V1 Mira variable Period = 551 days Amplitude ΔK = 1.22 mag J-Ks =4.1 mag

  3. Mira variables are; Large amplitude, pulsating AGB stars. Useful properties; 1. They obey a period- bolometric magnitude relation. 2. Their initial (and probably final) Mass increases with period. 3. Their age decrease with period. 551 day Mira expected to be intermediate age objects

  4. Next Surprise SPITZER spectra show Lynga V1 is a carbon star Carbon Miras with ~500 day period And very red colours (due to dust shells) Are found in intermediate age clusters Not globular clusters And have initial masses of ~1.5 solar masses An ages of ~1-2 Gyr

  5. Cluster velocity (Saviane et al. 2012) +22±3 km/s V1 +27±5 km/s Predicted velocity if in field –81 km/s Bolometric Mag. from PL –5.2 mag Bolometric Mag. If cluster member –5.0 mag

  6. Thus ~ 1.5 solar mass ~ 1.5 Gyr old Mira variable in a ~ 13 Gyr old globular cluster

  7. Comparison with collisional and binary-evolution models. FR Ferraro et al. Nature462, 1028-1031 (2009) doi:10.1038/nature08607

  8. Which sequence is most likely For the Lynga 7 Mira? If matter transferred has changes composition (H/He) It will affect later evolution Possibly direct collision most likely?

  9. Are merged stars important in other contexts? Does Galactic Bulge contain young And intermediate age stars?

  10. The two blue straggler sequences of M30. FR Ferraro et al. Nature462, 1028-1031 (2009) doi:10.1038/nature08607

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