star formation at high angular resolution iau symposium 221, sydney 2003 t tauri multiple systems...
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Star Formation at High Angular Resolution
IAU Symposium 221, Sydney 2003
T Tauri Multiple SystemsT Tauri Multiple Systems
Alexis BrandekerStockholm Observatory
Collaborators:
Ray Jayawardhana, René Liseau, Pawel Artymowicz, Joan Najita, Diego Mardones, and
Karl Haisch
Star Formation at High Angular Resolution
IAU Symposium 221, Sydney 2003
Why study multiple T Tauri stars?
• Most star systems are multiple – single stars are in minority
• Binaries provide dynamical masses of, and distances to, star systems, thereby contributing invaluable constraints on stellar evolution models
• High spatial resolution needed to avoid confusion, critical for accurate positioning in H-R diagram and evaluating SED
Star Formation at High Angular Resolution
IAU Symposium 221, Sydney 2003
Multiple?
1”
Examples:
Star Formation at High Angular Resolution
IAU Symposium 221, Sydney 2003
Multiple!
1”
T Tau S 18 (in MBM 12) VW Cha Keck AO Keck AO ESO 3.6 AO d~140 pc d~275 pc d~160 pc
Du
ch
ên
e,
Gh
ez,
& M
cC
ab
e 2
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Ap
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Bra
nd
eker,
Jayaw
ard
han
a,
& N
ajita
20
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, A
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eker
et
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20
01
, A
pJL
92 mas63 mas 100 mas
Star Formation at High Angular Resolution
IAU Symposium 221, Sydney 2003
Multiples indeed• T Tauri stars show a multiple frequency
significantly exceeding the corresponding frequency among MS field stars (e.g. Duquennoy & Mayor 1991, A&A; Reipurth & Zinnecker 1993, A&A; Duchêne 1999, ApJ; Barsony, Koresko, & Matthews 2003, ApJ; previous talks by Tom Greene and Ralph Launhardt)
• Proposed explanations:– Sensitivity (Ghez 1996, White & Ghez 2001, ApJ )
– Environment (Duchêne 1999, ApJ; Woitas, Leinert & Köhler 2001, A&A)
– Dynamical evolution (ejection), (Reipurth 2000, ApJ; Bate, Bonnell, & Bromm 2002 & 2003, MNRAS)
Star Formation at High Angular Resolution
IAU Symposium 221, Sydney 2003
Companion
ejection?
• Speckle: Koresko 2000, ApJL• AO: Köhler, Kasper, & Herbst 2000, IAU200• AO: Duchêne, Ghez, & McCabe 2002, ApJ• VLBI: Smith et al. 2003, A&A
Loinard, Rodríguez,& Rodríguez 2003,
ApJL
T Tauri SouthT Tauri South
Star Formation at High Angular Resolution
IAU Symposium 221, Sydney 2003
Spatial vs. spectral
• With diffraction limited NIR observations of 8-10 m class telescopes we reach resolutions of 40-50 mas, corresponding to 2-3 AU at 50 pc (distance to TWA), or 6-8 AU at 150 pc.
• A few AU orbital radius mean a few years orbital period – closing the sensitivity gap to the spectroscopic surveys for binaries and opening for dynamical mass estimates.
Brandeker, Jayawardhana,& Najita 2003, AJ
~3 AU,>~ 5 yr
Star Formation at High Angular Resolution
IAU Symposium 221, Sydney 2003
Dynamical mass determination:NTT 045251 + 3016
HST/FGS Steffen et al. 2001, ApJ
Orbital motion seen spatially and radially determines:• Period 6.91±0.04 yr• Major axis 4.8±0.4 AU
• M1 = 1.5±0.2 Msun
• M2 = 0.8±0.1 Msun
• Distance 145±9 pc• + more...
Star Formation at High Angular Resolution
IAU Symposium 221, Sydney 2003
Recent VLT/NACO imaging of
Cha association
1” VLM companion candidate?H=4 mag, sep=0.17”
Jayawardhana, Haisch, Brandeker, & Mardones (in prep.)
Star Formation at High Angular Resolution
IAU Symposium 221, Sydney 2003
VLT/NACOcontrast sensitivity
VLM companion candidate M
*=20MJ
M*=15MJ
M*=10MJ
10 Myr BD models from Baraffe et al. 2003, A&A
M*= 5MJ
Star Formation at High Angular Resolution
IAU Symposium 221, Sydney 2003
Conclusions
• Ongoing and future AO & spectral surveys for multiple T Tauri star will firmly establish the mf(sep,age) - down to ~ 20 MJ.
• Within a few years, accurate dynamical mass estimates of a number of PMS stars will provide strong constraints on the theory of star formation and early evolution
Star Formation at High Angular Resolution
IAU Symposium 221, Sydney 2003
Post-processing: Myopic deconvolution
VW Cha – Brandeker et al. 2001, ApJL
Star Formation at High Angular Resolution
IAU Symposium 221, Sydney 2003
Duchêne 1999, ApJ 341:547
Star Formation at High Angular Resolution
IAU Symposium 221, Sydney 2003
References• Barsony, Koresko, & Matthews 2003, ApJ 591:1064• Bate, Bonnell, & Bromm 2002, MNRAS 336:705• Bate, Bonnell, & Bromm 2003, MNRAS 339:577• Baraffe, Chabrier, Barman, Allard, & Hauschildt. 2003, A&A 402:701• Brandeker, Jayawardhana, & Najita 2003, AJ (in press)• Brandeker, Liseau, Artymowicz, & Jayawardhana. 2001, ApJ 561:L199• Duchêne 1999, ApJ 341:547• Duchêne, Ghez, & McCabe 2002, ApJ 568:771• Duquennoy & Mayor 1991, A&A 248:485• Ghez 1996, in Evolutionary Processes in Binary Stars, eds. Wijers, Davies, &
Tout, 477• Koresko 2000, ApJ 531:L147• Köhler, Kasper, & Herbst 2000, IAU200• Loinard, Rodríguez, & Rodríguez 2003, ApJ 587:L47• Mamajek, Lawson, & Feigelson 1999, ApJ 516:L77• Mardones, Jayawardhana, Haisch, & Brandeker 2003, ESO prop. 70C-0286A• Reipurth 2000, ApJ 120:3177• Reipurth & Zinnecker 1993, A&A 278:81• Smith, Pestalozzi, Güdel, Conway, & Benz 2003, A&A (in press)• Steffen, Mathieu, Lattanzi, et al. 2001, ApJ 122:997• White & Ghez 2001, ApJ 556:265• Woitas, Leinert & Köhler 2001, A&A 276:982