CHARA Collaboration Year-Five Science Review

Dynamite Diameters

Tabetha BoyajianGSU/CHARA

Presented by Hal McAlister

CHARA Collaboration Year-Five Science Review

Goals• To measure the angular diameter (θ) of a

large sample of A, F, and G main sequence stars with the CHARA Array to better than 4% accuracy– Establish effective temperatures to better

than 2%– Absolute luminosity HR diagram– Test stellar evolution models

• Metallicity and age• Duplicity

– Rotation effects

CHARA Collaboration Year-Five Science Review

Target Selection• HIPPARCOS Catalogue Query

– Spectral type: defined by B-V colors– Distance limit: Estimated radii from

spectral types gives maximum distance (i.e. angular size) for each spectral type. • The error on diameter is directly related to how

far down the visibility curve that you can sample. For 4% accuracy, limits are θ >0.65 mas in K-band and θ>0.50 mas in H band

– Folding in CHARA declination and magnitude observing limits and and filtering out the abnormal stars, there are ~90 stars, all with θ<1.7 mas, 25 with θ>1.0 mas

CHARA Collaboration Year-Five Science Review

Observing Dynamite Diameters

• 50 stars observed over the past 2 years– 20 G stars, 22 F stars and 8 A stars

• Observed on more than one – Date– Baseline– Calibratorto obtain highly reliable (and precise)

angular diameters for the program stars

• H-band data acquisition not successful

CHARA Collaboration Year-Five Science Review

Examples

CHARA Collaboration Year-Five Science Review

Examples

CHARA Collaboration Year-Five Science Review

Empirical HR Diagram• Linear radii

– The measured angular diameter combined with the parallax gives the linear radius of the star

• Effective temperatures– The measured angular diameter combined with

the bolometric flux gives the effective temperature of the star

CHARA Collaboration Year-Five Science Review

Fundamentally determined plot from the observations to-date. The size of circle represents the linear size of the star. The 1-σ errors are indicated.

HD 122563

61 Cyg A + B (K5V + K7V)

K0A0 G0F0

HD 103095 (G8Vp)

Sun (G2V)

K7

μ Cas A (G5Vp); σ Dra (K0V)

HD 195564 (G6 IV)

HD 81937 (F0IV)

HD 177724 (A0Vn)

HD 58946 (F0V)

HD 95418 (A1V)

HD 48737 (F5IV)

CHARA Collaboration Year-Five Science Review

An Interferometric HR DiagramAn Interferometric HR DiagramCompliments of Tabetha BoyajianCompliments of Tabetha Boyajian

An Interferometric HR DiagramAn Interferometric HR DiagramCompliments of Tabetha BoyajianCompliments of Tabetha Boyajian

CHARA Collaboration Year-Five Science Review

Red Giants in the HyadesRed Giants in the HyadesKnown Cluster Age is an Asset in ModelingKnown Cluster Age is an Asset in Modeling

Red Giants in the HyadesRed Giants in the HyadesKnown Cluster Age is an Asset in ModelingKnown Cluster Age is an Asset in Modeling

CHARA Collaboration Year-Five Science Review

625 Myr (Padova) isochrones with slightly varying heavy element abundances for existing and new results for Hyades giants.

CHARA values show the stars sitting pretty on the Red Giant Clump.

Red Giants in the HyadesRed Giants in the HyadesBoyajian et al. Boyajian et al. ApJApJ 2009. 2009.

Red Giants in the HyadesRed Giants in the HyadesBoyajian et al. Boyajian et al. ApJApJ 2009. 2009.

CHARA Collaboration Year-Five Science Review

First Diameter for a Population II StarFirst Diameter for a Population II StarFirst Diameter for a Population II StarFirst Diameter for a Population II Star

Cas A

CHARA Collaboration Year-Five Science Review

Diameter of Low-Metallicity Star µ Cas ADiameter of Low-Metallicity Star µ Cas ABoyajian et al. Boyajian et al. ApJApJ 2008. 2008.

Diameter of Low-Metallicity Star µ Cas ADiameter of Low-Metallicity Star µ Cas ABoyajian et al. Boyajian et al. ApJApJ 2008. 2008.

Figure shows radii for EBs and LBOI targets for G to mid-K along with ZAMS for 3 target stars and the evolutionary track for µ Cas A. Models (Y2 and V-R) for such metal-poor stars obviously need improvement.

For µ Cas A:

LD = 0.973 ± 0.009 mas