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Detection of FIP Effect on Late-type Giants

Detection of FIP Effect on Late-type Giants. Coronal Abundances and Thermal Structure The late-type giants b Ceti, 31 Com and m Vel Objects and Observations features The DEMs and Coronal Abundances Conclusions. D. Garcia-Alvarez, J.J. Drake, L.Lin, V. Kashyap and B.Ball

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Detection of FIP Effect on Late-type Giants

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  1. Detection of FIP Effect on Late-type Giants • Coronal Abundances and Thermal Structure • The late-type giants b Ceti, 31 Com and mVel • Objects and Observations features • The DEMs and Coronal Abundances • Conclusions D. Garcia-Alvarez, J.J. Drake, L.Lin, V. Kashyap and B.Ball Smithsonian Astrophysical Observatory

  2. Coronal Abundances and Thermal Structure Why derive Stellar Coronal Abundances? • Abundance anomalies (FIP and inverse-FIP effect, flares). • Larger range of stars is needed. • It will help to interpret X-ray observations of stars. Why/how to derive the Coronal Thermal Structure? • Key to understanding the coronal heating. • Must be known before elemental abundances can be determined. • Abundance-independent structure obtained by using ratios of ions from same element.

  3. Objects and Observations Features Stellar photospheric abundances

  4. The Observed Spectra

  5. The Differential Emission Measurements • Same slope/shape for the low temperature range. • A plateau around log T[K]~6.8±0.2 is observed in  Ceti and  Vel. • Smooth increase and peak at log T[K]~7.1 is observed in 31 Com. • Little evidence for substantial amount of plasma at log T[K]>7.3.

  6. The Synthetic Spectrum

  7. We observe solar-like FIP effect for  vel and  Ceti. No clear effect is seen in 31 Com. • Coronae Na-rich agree with predictions for F-K giants (Drake & Lambert 1994). • O-Na anti-correlation possibly due to very deep mixing (Langer & Hoffman 1998). • No clear dependency on rotational velocity ( Ceti vsini~3 km/s, 31 Com vsini~67 km/s). • Structural changes might produce the observed coronal pattern. Finally … the Coronal Abundances

  8.  Ceti + 31 Com = Capella ?

  9. Conclusions • The late-type giants Ceti, 31 Com and  Vel share similarities in coronal composition. • We detected a solar-like FIP effect for  Ceti and  Vel but not for 31 Com. • No clear dependency between rotational velocity and FIP trend. • Structural changes during their evolution might produce the observed coronal pattern in late-type giants.

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