1. prospects for planet formation in multiple stellar systems
© NASA/JPL/Caltech
Gaspard Duchêne (UC Berkeley, Observatoire de Grenoble)
prospects for planet formation in multiple stellar systems
Gaspard Duchêne − IAU XXVII General Assembly – SpS7 – Rio de Janeiro – August

2. Planets in multiple systems?
They must exist!
©® LucasFilm Ltd.
Gaspard Duchêne − IAU XXVII General Assembly – SpS7 – Rio de Janeiro – August

3. Some open questions Do planets form in multiple systems? YES !
Does the influence of a stellar companion affect the planet properties at all?
How different are the initial conditions for planet formation in multiple systems?
What do these systems teach us about the planet formation process?
Let’s summarize the empirical evidence…
Gaspard Duchêne − IAU XXVII General Assembly – SpS7 – Rio de Janeiro – August

4. Stellar multiplicity ~50% of all G type stars have a companion
Most companions are
on wide orbits (>10AU)
Mostly shorter Porb
for lower-mass stars
Even higher frequency
for PMS objects
Far from a marginal phenomenon ! 10
100 AU
Gaspard Duchêne − IAU XXVII General Assembly – SpS7 – Rio de Janeiro – August

5. Protoplanetary disks Planet-forming disks have sizes ≥ 100 AU
Only a (small) fraction of the mass resides within AU, where planets form
Importance of total reservoir and viscous accretion?
Andrews & Williams (2007)
10 AU
100 AU
Gaspard Duchêne − IAU XXVII General Assembly – SpS7 – Rio de Janeiro – August

6. Outline The basics of stellar multiplicity and disks
Multiple stars and …
Protoplanetary disks (initial conditions)
Debris disks (early stages)
Planetary systems (mature systems)
Back to the big picture
Gaspard Duchêne − IAU XXVII General Assembly – SpS7 – Rio de Janeiro – August

7. Primordial disks
Truncated disks among Pre-Main Sequence stars have been found in a number of systems
Radii roughly match theoretical predictions
 to within a factor of 2 (not so great…)
GG Tau
HV Tau
CoKu Tau /4
Poster 24 (Romero)
Krist et al. (2005)
Stapelfeldt et al. (2003)
D’Alessio et al. (2005)
Ireland & Kraus (2008)
Gaspard Duchêne − IAU XXVII General Assembly – SpS7 – Rio de Janeiro – August

8. Primordial disks in binaries
Usually both stars have a disk, but disks around primaries
are more massive
tend to survive longer (?)
Primaries offer better
grounds to form planets
Poster 9 (Petr-Gozens)
A. Kraus’ talk
Jensen & Akeson (2003)
see Patience et al. (2008), Monin et al. (2007, PPV)
Gaspard Duchêne − IAU XXVII General Assembly – SpS7 – Rio de Janeiro – August

9. Primordial disks: inner regions
When present in binary systems, disks have similar properties in the planet-forming region
 crude probes (inner disk surface only)
Silicate feature
grain size
NIR colors
flaring
disk
dust evolution
Pascucci et al. (2008)
from Cieza et al. (2009)
see also White & Ghez (2001)
Gaspard Duchêne − IAU XXVII General Assembly – SpS7 – Rio de Janeiro – August

10. Primordial disks: total mass
Early evidence for a limited mass reservoir in tight binaries confirmed with larger samples
 Md ≠ F850μm
However massive disks exist around some spectroscopic binaries!
 3mm flare in DQ Tau
[poster 25 (Salter)]
3 AU
30 AU
from Andrews & Williams (2005, 2007)
+ Henning et al. (1993), Jensen et al. (1996),
Mathieu et al. (1995)
Gaspard Duchêne − IAU XXVII General Assembly – SpS7 – Rio de Janeiro – August

11. Primordial disks: dissipation?
Tight binaries (≤ 30 AU) have a much lower occurrence of disks than wide ones
Clearing during formation?
Fast dissipation?
No replenishment?
 incompleteness
A. Kraus’ talk
Tau, Oph,
Cha I, CrA
~1 Myr
Cieza et al. (2009)
see also Bouwman et al. (2006),
Damjanov et al. (2009) 25
100 AU
Gaspard Duchêne − IAU XXVII General Assembly – SpS7 – Rio de Janeiro – August

12. Outline The basics of stellar multiplicity and disks
Multiple stars and …
Protoplanetary disks (initial conditions)
Debris disks (early stages)
Planetary systems (mature systems)
Back to the big picture
Gaspard Duchêne − IAU XXVII General Assembly – SpS7 – Rio de Janeiro – August

13. Debris disks
Some well-known debris disks are members of binary/multiple systems
Mostly around (higher-mass) primaries
Even some circumbinary debris disks!
HR 4796 (500 AU)
HD (170 AU)
V4046 Sgr (2.4 d)
© NASA/JPL/Caltech
© D. Aguilar; J. Kastner
Debbes et al. (2008)
Gaspard Duchêne − IAU XXVII General Assembly – SpS7 – Rio de Janeiro – August

14. Debris disks: frequency
Binaries among known debris disks: 15-25%
Mannings & Barlow (1998), Plavchan et al. (2009)
 binary surveys incomplete, especially for A stars
“If anything, stars in binary systems show less excess emission” (Rieke et al. 2005)
Detection rate in binaries ~ 33%, slightly higher than among singles
Trilling et al. (2007)
Debris disks in binaries are common!
Gaspard Duchêne − IAU XXVII General Assembly – SpS7 – Rio de Janeiro – August

15. Debris disks: separation trend
Not all binaries are equal for debris disks
~ AU binaries have few debris disks
 ≠ Teff ≠ disk radii probed
© Tim Pyle – SSC/NASA
113 AFGK stars
Trilling et al. (2006)
Rodriguez, Zuckerman et al. (in prep.)
but see Plavchan et al. (2009) & poster 37
63 AF stars
Gaspard Duchêne − IAU XXVII General Assembly – SpS7 – Rio de Janeiro – August

16. Outline The basics of stellar multiplicity and disks
Multiple stars and …
Protoplanetary disks (initial conditions)
Debris disks (early stages)
Planetary systems (mature systems)
Back to the big picture
Gaspard Duchêne − IAU XXVII General Assembly – SpS7 – Rio de Janeiro – August

17. Exoplanets One of the pulsar planets is circumbinary
First planets in Main Sequence binary systems reported as early as 1997 (Butler et al.)
PSR
γ Cep
© Greg Bacon – STScI/NASA
© Tim Jones – McDonald Obs.
Gaspard Duchêne − IAU XXVII General Assembly – SpS7 – Rio de Janeiro – August

18. Exoplanets: architecture
Most planets are found around primaries
Exceptions: 16 Cyg B, HD B
 few searches around (lower mass) companions
A handful of planets in triple systems
Usually (A-b) – (B-C)
Extreme case: γ Cep
Planet: a=2 AU, e=0.2
Comp: a=20 AU, e=0.4
planet
companion
Raghavan et al. (2006)
Gaspard Duchêne − IAU XXVII General Assembly – SpS7 – Rio de Janeiro – August

19. Exoplanets: multiplicity
~33% of known exoplanet hosts are binaries
Slightly lower rate than among singles
Patience et al. (2002), Raghavan et al. (2006), Bonavita & Desidera (2007), Mugrauer & Neuhauser (2009)
 negative selection bias!
Possible deficit of planets
if separation ≤ 100 AU
Need better statistics
Eggenberger et al. (2009)
Gaspard Duchêne − IAU XXVII General Assembly – SpS7 – Rio de Janeiro – August

20. Exoplanets: finer dependencies
Early studies suggested a peculiar trend
Close-in planets in binaries are more massive
No trend in larger sample (nor with e)
But …
Zucker & Mazeh (2002)
From Exoplanet Encyclopedia and Mugrauer & Neuhauser (2009)
Gaspard Duchêne − IAU XXVII General Assembly – SpS7 – Rio de Janeiro – August

21. Exoplanets: finer dependencies
Planets in wide systems are indistinguishable from those around single stars
Planets in tight binaries have higher masses
Mugrauer et al. (2007),
Desidera & Barbieri (2007),
No influence of separation
on Porb, e distributions
From Exoplanet Encyclopedia and
Mugrauer & Neuhauser (2009)
Gaspard Duchêne − IAU XXVII General Assembly – SpS7 – Rio de Janeiro – August

22. Outline The basics of stellar multiplicity and disks
Multiple stars and …
Protoplanetary disks (initial conditions)
Debris disks (early stages)
Planetary systems (mature systems)
Back to the big picture
Gaspard Duchêne − IAU XXVII General Assembly – SpS7 – Rio de Janeiro – August

23. Planet formation in binaries
Binaries with separations down to ~50 AU have little influence on protoplanetary, debris disks and exoplanetary systems
Despite truncation, only the inner AU matter!
Core accretion scenario can work, if sufficient mass is available
This is roughly half of all solar-type binaries!
Some 50-75% of stars can form planets
Gaspard Duchêne − IAU XXVII General Assembly – SpS7 – Rio de Janeiro – August

24. Planet formation in binaries
Binaries with separations of a few to a few tens of AU are highly disruptive!
Not such a major surprise after all…
But some planets form in such environments!
Where is the material coming from?
What do disks disappear faster?
Why do planets tend to be of higher mass?
Disk instability scenario could work (a la Boss)
Gaspard Duchêne − IAU XXVII General Assembly – SpS7 – Rio de Janeiro – August

25. Planet formation in binary systems
How about planets in tight binaries (< 1-2 AU)?
Protoplanetary disks offer sound initial conditions
Debris disks show that planetesimals formed
Models suggests that they can easily form
Circumbinary planets are very likely to exist, but they will remain highly elusive to us
Gaspard Duchêne − IAU XXVII General Assembly – SpS7 – Rio de Janeiro – August