Detection of FIP Effect on Late-type Giants

D. Garcia-Alvarez, J.J. Drake, L.Lin, V. Kashyap and B.BallD. Garcia-Alvarez, J.J. Drake, L.Lin, V. Kashyap and B.BallSmithsonian Astrophysical ObservatorySmithsonian Astrophysical Observatory

• Coronal Abundances and Thermal StructureCoronal Abundances and Thermal Structure

• The late-type giants The late-type giants Ceti, 31 Com and Ceti, 31 Com and VelVel Objects and Observations featuresObjects and Observations features The DEMs and Coronal AbundancesThe DEMs and Coronal Abundances ConclusionsConclusions

Coronal Abundances and Thermal Coronal Abundances and Thermal StructureStructure

• Abundance anomalies (FIP and inverse-FIP effect, flares).Abundance anomalies (FIP and inverse-FIP effect, flares).• Larger range of stars is needed.Larger range of stars is needed.• It will help to interpret X-ray observations of stars. It will help to interpret X-ray observations of stars.

Why derive Stellar Coronal Abundances?Why derive Stellar Coronal Abundances?

Why/how to derive the Coronal Thermal Structure?Why/how to derive the Coronal Thermal Structure?

• Key to understanding the coronal heating.Key to understanding the coronal heating.

• Must be known before elemental abundances can be Must be known before elemental abundances can be determined.determined.

• Abundance-independent structure obtained by using ratios of Abundance-independent structure obtained by using ratios of ions from same element.ions from same element.

Objects and Observations Objects and Observations FeaturesFeatures

Stellar photospheric abundances

The Observed SpectraThe Observed Spectra

The Differential Emission The Differential Emission MeasurementsMeasurements

• Same slope/shape for the low temperature range.Same slope/shape for the low temperature range.

• A plateau around log T[K]~6.8±0.2 is observed in A plateau around log T[K]~6.8±0.2 is observed in Ceti and Ceti and Vel.Vel.

• Smooth increase and peak at log T[K]~7.1 is observed in 31 Smooth increase and peak at log T[K]~7.1 is observed in 31 Com.Com.

• Little evidence for substantial amount of plasma at log Little evidence for substantial amount of plasma at log T[K]>7.3.T[K]>7.3.

The Synthetic SpectrumThe Synthetic Spectrum

Finally Finally …… the Coronal Abundances the Coronal Abundances

• We observe solar-like FIP effect for We observe solar-like FIP effect for vel and vel and Ceti. No clear effect is seen in 31 Ceti. No clear effect is seen in 31 Com.Com.

• Coronae Na-rich agree with predictions for F-K giants (Drake & Lambert 1994).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). O-Na anti-correlation possibly due to very deep mixing (Langer & Hoffman 1998).

• No clear dependency on rotational velocity (No clear dependency on rotational velocity ( Ceti vsini~3 km/s, 31 Com vsini~67 Ceti vsini~3 km/s, 31 Com vsini~67 km/s).km/s).

• Structural changes might produce the observed coronal pattern.Structural changes might produce the observed coronal pattern.

Ceti + 31 Com = Capella ?Ceti + 31 Com = Capella ?

ConclusionsConclusions• The The late-type giantslate-type giants Ceti, 31 Com and Ceti, 31 Com and Vel Vel

share share similarities in coronal compositionsimilarities in coronal composition..

• We detected a We detected a solar-like FIP effect solar-like FIP effect for for Ceti and Ceti and VelVel but not for 31 Com. but not for 31 Com.

• No clear dependencyNo clear dependency between between rotational velocityrotational velocity and and FIP trendFIP trend..

• Structural changesStructural changes during their evolution might during their evolution might produceproduce the observed the observed coronal patterncoronal pattern in late-type in late-type giants.giants.