Carlos A. O. Torres & Germano R. Quast ( LNA / MCT/BRAZIL )

1. Small Loose Young AssociationsThe SACY ProjectSearch for Associations ContainingYoung stars Carlos A. O. Torres & Germano R. Quast (LNA / MCT/BRAZIL) Claudio H. F. Melo & Michael Sterzik (ESO) Ramiro de la Reza & Licio da Silva (ON / MCT/BRAZIL)

2. Background • 80’s - Isolated T Tauri stars? • 89 - New T Tauri stars found around TW Hya • 90’s - PDS (IRAS) • 2000 - Horologium Association (ROSAT) & Tucana Association  Both nearby (~50 pc), adjacent, with similar kinematics and ages  a unique and large association?  Others?

3. Sample definition • ROSAT All-Sky Bright Source Catalogue • Proper motions from Hipparcos or Tycho-2 Catalogues • (B-V)  0.6 (later than G0) • Excluding known RS CVn, W UMa, giants, etc (SIMBAD) • Excluding Mv < 2.0 (or L < 10 Lʘ  ages > 5 Myr)

4. Goals • Li abundance • Metallicity • Radial and Rotational Velocities • Duplicity • Evolutionary stage

5. Instruments • FEROS (ESO - 1.52 m & 2.2m) • Coudé (OPD/LNA - 1.60m) • CORALIE (ESO - Swiss Euler Telescope)

6. Southern ROSAT Sources SACY [Hip + TYC & (B-V)0.6] Observed objects (not sources) Data from literature 9574 1953 1750 150 Statistics

11. Giants  17% Dwarfs (IV & V)  83%  Young stars (*)  39% Pleiades age  22% Old stars  39% RESULTS SB 10%  16%  38% (*) Includes dwarf stars later than M0

12. UVW from stars with parallaxes UVW taken from literature UVW from6D clusteringanalysis Age from Li strength or Isochrone fitting 1st step – look for concentration in the UVW space Concentration detectedaround U0V0W0Group/Association?

13. Minimize: Loop over all young objectsin the catalogue σ= Out of ad-hoc XYZ constraints to the member list? Probabilities? New ad-hoc XYZ constraints? New limits: F or σ? Yes 2nd step - Loop over catalogue until convergence is reached Star rejected No Add star to Member list Compute newU0V0W0 usingnew member list

14. COMPARISON OF THE AD-HOC CURVES TO BARAFFE MODELS 5 Myr 10 Myr 50 Myr 100 Myr

15. Expansion of the Associations in X direction Within β PicA

16. Concentration in the UVW space:U=-10.1 V=-15.9 W=-9.1  The β Pic Association 46 Members

17. ʘ ʘ ʘ

18. 5 Myr 10 myr 70 myr β Pic Association

19. β Pic Association S N

20. Concentration in the UVW space:U=- 9.6 V=-20.9 W=-1.3U=-12.7 V=-21.9 W=-5.6U=-10.5 V=-23.2 W=-4.3  The GAYA Complex: Tuc-HorA: 36 Members ColA: 27 Members CarA: 21 Members

21. ʘ ʘ ʘ

22. 5 Myr 10 Myr 30 Myr 70 Myr Green Tuc-HorA White ColA Red CarA GAYA Complex

24. Concentration in the UVW space:U=-10.5 V=-18.0 W=-4.9  The TW Hya Association 22 Members

25. ʘ ʘ ʘ

26. 5 Myr 8 Myr TWA 20 70 Myr TW Hya Association

28. Concentration in the UVW space:U=-11.0 V=-19.9 W=-10.4  The ε Cha Association 24 Members (4 from η Cha)

29. ʘ ʘ ʘ

30. 5 Myr 10 Myr 70 Myr Red Field Members Green η Cha C. Members Blank Others η Cha Cluster ε Cha Association

32. Concentration in the UVW space:U=-13.6 V=-2.7 W=-9.4  The Octantis Association 11 Members

33. ʘ ʘ ʘ

34. 5 Myr 10 Myr 70 Myr Oct Association

36. Concentration in the UVW space:U=-22.0 V=-14.4 W=-5.0  The Argus Association 63 Members (35 from IC 2391)

37. ʘ ʘ ʘ

38. 5 Myr 10 Myr 30 Myr 70 Myr Red Field Members Green IC 2391 Members Argus Association

40. Concentration in the UVW space:U=-6.8 V=-27.2 W=-13.3  The AB Dor Association 75 Members

41. ʘ ʘ ʘ

42. 5 Myr 10 Myr 70 Myr AB Dor Association

43. N S AB Dor Association

50. Insights • The distribution of young stars in the solar neighborhood is patchy, forming huge kinematical associations. • We recognize at least 14 young associations in the SACY database (there are five more possible associations to verify) .