2. Small Loose Young Associations The SACY Project Search for Associations Containing Young 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)

3. 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? Background

4. 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 M v 5 Myr)

5. Goals  Li abundance  Metallicity  Radial and Rotational Velocities  Duplicity  Evolutionary stage

6. Instruments YFEROS (ESO - 1.52 m & 2.2m) YCoudé (OPD/LNA - 1.60m) YCORALIE (ESO - Swiss Euler Telescope)

7. Statistics n Southern ROSAT Sources n SACY [Hip + TYC & (B-V)  0.6] n Observed objects (not sources) n Data from literature Ü9574 Ü1953 Ü1750 Ü150

12. RESULTS ïGiants  17% ïDwarfs (IV & V)  83%  íYoung stars (*)  39% íPleiades age  22% íOld stars  39% SB  10%  16%  38% (*) Includes dwarf stars later than M0

13. UVW from stars with parallaxes UVW from 6D clustering analysis UVW taken from literature Concentration detected around U 0 V 0 W 0 Group/Association? Age from Li strength or Isochrone fitting 1 st step – look for concentration in the UVW space

14. σ= Out of ad-hoc XYZ constraints to the member list? Loop over all young objects in the catalogue Minimize: Star rejected Yes Add star to Member list No Compute new U 0 V 0 W 0 using new member list 2 nd step - Loop over catalogue until convergence is reached Probabilities? New ad-hoc XYZ constraints? New limits: F or σ?

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

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

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

18. ʘ ʘ ʘ

19. 5 Myr 10 myr 70 myr β Pic Association

20. N S

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

22. ʘ ʘ ʘ

23. 5 Myr 10 Myr 30 Myr 70 Myr GAYA Complex Green Tuc-HorA White ColA Red CarA

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

26. ʘ ʘʘ

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

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

30. ʘ ʘ ʘ

31. 5 Myr 10 Myr 70 Myr ε Cha Association Red Field Members Green η Cha C. Members Blank Others η Cha Cluster

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

34. ʘ ʘ ʘ

35. 5 Myr 10 Myr 70 Myr Oct Association

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

38. ʘ ʘʘ

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

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

42. ʘ ʘʘ

43. AB Dor Association 5 Myr 10 Myr 70 Myr

44. AB Dor Association NS

45. AssociationNAge U σ V σ W σEXP β Pic4610-10.12.1-15.90.8 -9.10.9 Y Tuc- Hor3630 -9.60.9-20.90.8 -1.30.9 Y Col2730-12.71.1-21.90.8 -5.60.9 Y Car2130-10.50.4-23.20.8 -4.31.6 Y? TW Hya22 8-10.50.9-18.01.5 -4.00.9 Y ε Cha24 6-11.01.2-19.91.2-10.41.6 N? Oct1110-13.62.5 -2.71.4 -9.41.0 Y Argus6340-22.00.3-14.41.3 -5.01.3 N AB Dor7570 -6.81.3-27.21.1-13.31.5 N

51. 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).