Cluster & Association Cluster & Association MembersMembers

Ernst PaunzenErnst PaunzenIfA, ViennaIfA, Vienna

Why consider Clusters Why consider Clusters Members?Members?

Clusters offer astrophysical Clusters offer astrophysical properties “for free”:properties “for free”:

1.1. AgeAge2.2. DistanceDistance3.3. ReddeningReddening

Not depending on any Not depending on any temperature, log g, absolute temperature, log g, absolute magnitude calibrationmagnitude calibration

The BRITE HRDThe BRITE HRDWithout reddening: M(V) = -5 mag and V = 4 mag => distance = 630 pc

-6; 4; 1000-5; 4; 630-4; 4; 400-3; 4; 250-2; 4; 160-1; 4; 100+0; 4; 65

Clusters within 750 pcClusters within 750 pc-6; 4; 1000-5; 4; 630-4; 4; 400-3; 4; 250-2; 4; 160-1; 4; 100+0; 4; 65

log t < 8.0 (blue)log t < 9.0 (yellow)log t > 9.0 (red)

Several Cluster Members in the BRITE sample!

WEBDA: http://www.univie.ac.at/webda

Cluster Properties and Cluster Properties and MembershipMembership

Cluster formation within a few Cluster formation within a few MyrsMyrs

From one large Molecular CloudFrom one large Molecular Cloud Membership criteria due to proper Membership criteria due to proper

motions and radial velocitiesmotions and radial velocities

Isochrones IIsochrones I

Padova Isochrones

Isochrones IIIsochrones II

280KHuge Errors!

Lines of Equal MassesLines of Equal Masses2.

5 m

agError:M(V) = 0.1 magMass = 0.1 M(sun)

+ Error in log Teff

Padova Isochrones

Precision of Age DeterminationPrecision of Age Determination

Values from the Literature Paunzen & Netopil, 2006, MNRAS, 371, 1641

Why consider Clusters Why consider Clusters Members?Members?

Clusters offer astrophysical Clusters offer astrophysical properties “for free”:properties “for free”:

1.1. Age, error about 15%Age, error about 15%2.2. Distance, error less than 10%Distance, error less than 10%3.3. Reddening, error less than 5%Reddening, error less than 5%

Values can be improved!Values can be improved! ““Only positive membership needed” Only positive membership needed” Precise mass estimation possiblePrecise mass estimation possible Huge data base (WEBDA) in ViennaHuge data base (WEBDA) in Vienna