1. Direct imaging of substellar objects around young and nearby stars: The SACY sample N. Huélamo (Laeff-INTA, Spain) H. Bouy (UC Berkeley) C. Torres (LNA, Brazil) C. Melo, M. Sterzik (ESO, Chile) G. Chauvin (LAOG, France) D. Barrado y Navascués (Laeff-INTA, Spain)

2. Motivation of this work Direct images of Substellar/planetary companions Observations are the only way to discriminate between formation theories. Put constraints to physical parameters: 1. Frequency of substellar objects in wide orbits 2. Characterize their atmospheres 3. Calibrate evolutionary models

3. Looking for star-companion systems High contrast imaging Companion to stars: We can assume similar distance/age Adaptive Optics + Large telescope High spatial resolution

4. What can we learn with AO imaging? Chauvin et al. 2007 AO ima & spec Population of BD/planets in large orbits Characterize the atmospheres of the objects Targets: Late-type Field stars ~M p *sin(i) orbital parameters

5. AO imaging: Where to look…. Substellar companions are normally searched around young ( < 100 Myr) and nearby (d < 100pc) late-type stars. WHY? CONTRAST Young late-type stars: The younger the substellar object, the brighter Nearby stars: we can probe smaller separations 7 log t 89 M primary (Msun) △K (mag) 1.07.5 0.56.6 0.14.3 10 M Jup @ 10 Myr

6. Deep surveys to detect substellar/planetary companions SURVEY Number Targets Age (Myr) Distance (pc) Chauvin et al (2003) 3.6/Adonis 24< 30 ≤ 50 Masciadri et al. (2005) NACO/VLT 3012-200 4-77 Biller et al. (2006) NACO/VLT + SDI 45≤ 250 ≤ 50 Kasper et al. (2007) NACO/VLT L-band 22≤ 30≤ 10 - 60 Lafreniere et al. (2007) Gemini+Altair 8530 - 5000 ≤ 35 And more to come…

7. Confirmed substellar companions Chauvin et al. 2007

8. Confirmed Substellar companions Most of the substellar companions to stars detected so far have been found at separations between 100-1000 AU. ~100 AU~ 330 AU~ 260 AU ~795 AU~475 AU HN Peg HD3651DH Tau AB Pic Neuhauser et al. 2004 Itoh et al. 2005 Chauvin et al. 2005 Burgasser et al. 2005 Luhman et al. 2007 ● 1 planetary-mass companion (substellar binary): sep~60 AU ● No planets (or BDs) detected at very small separations No >2 Mjup at sep. 45-200 AU No >4 Mjup at sep. 20-40 AU No >5 Mjup at sep > 15 AU Lafreniere et al. 2007 Kasper et al. 2007 Biller et al. 2006 Masciadri et al. 2005 Chauvin et al. 2005

9. What is SACY? What is the connection with substellar/planetary searches?

10. The SACY survey Search for Associations Containing Young stars Torres et al, 2003, Torres et al. 2006 - Started by Torres et al. in 2000 after the discovery of Tucana & Horologium (Torres et al. 2000, Zuckerman & Webb 2000) Moving groups of Post- T Tauri stars: How to identify them? T Tauri Stars (Age ~1 Myr) Post-T Tauri stars (10-100Myr) Near-IR excess (disks) X-ray emission can persist.. Forbidden lines (accretion) Lithium X-ray emission, Lithium, etc… - Aim: Search for young and nearby stars as optical counterparts to X- ray (ROSAT) detections d ~30 pc, age~30 Myr

11. The SACY project Southern ROSAT Sources SACY [Hip + TYC & (B-V)0.6] Observed objects (not sources) Data from literature Ü9574 Ü1953 Ü1750 Ü150 Torres et al. have identified at least 14 young associations in the SACY database (there are five more possible associations to confirm…). Lithium -- age estimation Dynamical properties + Convergence method: NEW MOVING GROUPS NEW MEMBERS of known assoc. } Li abundance Radial and Rot. velocity Torres et al. 2006; Torres et al. 2007 Prime targets for AO surveys to detect subs./planet. companions G0 and later…

12. Our study 1. VLT/NACO survey : Substellar/Planetary companions around new young nearby stars identified in the SACY survey 2. Characterization of nearby (young?) M-type stars in the SACY Catalog that do not belong to any moving group.

13. 1. Search for substellar companions around SACY stars The sample of 78 targets contains: I. 18 New identified members of 9 young and nearby loose associations included in Torres et al. 2007 (e.g. TW Hya, Beta Pic, Tuc-Hor) II. 30 New identified members in other nearby assocs. (e.g. LCC) III. 15 M-type stars without lithium and/or association but probably young… IV. 15 Young stars (with lithium) without association AO survey started on 2006

14. Average properties… Most of them are M,K-type stars Ages ~ 10 Myr Hipparcos and/or UCAC2 Proper motions: (Confirm companions in 1-2 yrs)

15. Observations NACO/VLT Optical WFS + IB2.27 filter S27 objective : 27’’ x 27’’ FOV Typical integrations of 12-15 minutes Classical AO imaging Service Observations (April-Sep. 2006)

16. Detection limits M * = 0.8 Msun, 10 Myr 30 60 90 120 300 (AU) @ 60pc 10M Jup Average curve for IB 2.27 Δmag ~ 7mag@0.5”

17. I: Nearby loose associations Number Assoc. AgeDistance 4 Є Cha 6 100 11 β Pic 10 60 3 Tuc-Hor 30

18. Results 67 detected sources around 12 stars All of them around BPA and ECA members 14 sources at separation < 5” 2 new subarsecond stellar binaries

19. Results

20. Targets at separations < 500 AU from host star: 4 in ECA 13 in BPA

21. The most interesting substellar candidates I. ε Cha Target: K0 star from Є Cha d=103 pc Age=6 Myr Sep=3.8”@103pc= 391AU 10 M Jup 20 M Jup Sep=0.13” @103 = 13.4 AU Galactic latitude ~ -8 deg

22. The most interesting substellar candidates I. ε Cha Target: G8 star from Є Cha d=115 pc Age=6 Myr Sep=1.8”@103pc= 185 AU Galactic latitude ~ -8 deg Companion Candidate: Sep = 210 AU Mass < 10 M Jup

23. The most interesting substellar candidates II. BPA Target: M1 star from β Pic d= 54 pc Age=10 Myr 3.9” Companion Candidate: Sep = 210 AU Mass < 10 M Jup Sep=3.9”@54pc= 210 AU Galactic Latitude ~ -23 deg

24. The most interesting substellar candidates II. BPA Target: M1 star from β Pic d= 72 pc Age=10 Myr 1.7” Companion Candidate: Sep = 126 AU Mass ~10 M Jup Sep=1.7”@72 pc= 126 AU Galactic Latitude ~ -07 deg

25. II: Lower Centaurus Crux (LCC) 11 new identified members Distances: 73-110pc Age ~ 8 Myr (Torres et al., in prep.)

26. Galactic latitudes (~ 0–8 deg) Substellar comp. candidates in LCC Results: 130 detected sources 25 at separations < 5” 4 new subarc. binaries

27. Substellar comp. candidates in LCC 40 M Jup @300 AU15 M Jup @260 AU Gal. Latitudes: ~02 deg

28. Subsamples I and II: Nature of the companion candidates? Closer companions (sep < 10 arcsec) Second epoch observations are needed… hopefully next semester Wider companions (sep > 10 arcsec): BACKGROUND cross-correlation with optical, near-IR catalogs

29. III: M-type stars from SACY Our SACY sample contains 15 M-stars (M0-M3): -With X-ray emission -Without lithium -Do not converge to any moving group -8 (out of 15) with Hipparcos parallaxes: d ~(14-59 pc) What is the nature of these stars? Are they young or old?

30. M-type stars from SACY Lithium cannot be used as an age estimator since it is depleted too fast. AB Dor – 70 Myr β Pic – 10 Myr …but gives as a lower limit age ≥ 10Myr

31. M-stars: Age diagnostics? - Comparison with Evol. Tracks - Stellar activity - Surface gravity

32. M-type stars from SACY Comparison with evolutionary tracks Song et al. 2003

33. M-type stars from SACY L x / L bol as age diagnostic Song et al. 2003

34. M⓪M⓪ M-type stars from SACY Surface Gravity can be used as an age indicator.

35. M-type stars from SACY Gravity sensitive lines: (e.g. Na I 5900 Å, KI D 7700 Å, Na I D 8200 Å) Method: - EW measurement of alkali lines - Comparison with templates: Younger and older stars with similar spectral types (on-going …)

36. Substellar companion candidates to M-stars? A DB white dwarf ‘companion’ to a nearby star 8.6” companion to a M1 star Sep. ~ 500 AU @ 59pc Mass ~ 20 M Jup @ 70 Myr Public Archives: the system is a common proper motion pair (obs from 1910 to 2006). BUT Colors not consistent with a Brown Dwarf but with a White Dwarf. He I lines

37. Conclusions SACY Catalog contains prime targets for AO surveys to look for substellar and planetary-mass companions: young and nearby Preliminary results from our NACO/VLT survey: 17 good substellar/planetary companion candidates to nearby stars in nearby associations. Several candidates around LCC stars but …at very low galactic latitudes (probably background…) Second epoch observations necessary… Increase the number of SACY young,nearby M-stars without association via optical, X-ray data (surface gravity, magnetic activity, etc..)