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 14 2009

Planets in multiple systems? They must exist! ©® LucasFilm Ltd. Gaspard Duchêne − IAU XXVII General Assembly – SpS7 – Rio de Janeiro – August 14 2009

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 14 2009

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 14 2009

Protoplanetary disks Planet-forming disks have sizes ≥ 100 AU Only a (small) fraction of the mass resides within 10-20 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 14 2009

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 14 2009

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 14 2009

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 14 2009

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 14 2009

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 14 2009

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 14 2009

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 14 2009

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 113766 (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 2009

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 14 2009

Debris disks: separation trend Not all binaries are equal for debris disks ~ 1-100 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 14 2009

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 14 2009

Exoplanets One of the pulsar planets is circumbinary First planets in Main Sequence binary systems reported as early as 1997 (Butler et al.) PSR 1620-26 γ Cep © Greg Bacon – STScI/NASA © Tim Jones – McDonald Obs. Gaspard Duchêne − IAU XXVII General Assembly – SpS7 – Rio de Janeiro – August 14 2009

Exoplanets: architecture Most planets are found around primaries Exceptions: 16 Cyg B, HD 178911 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 14 2009

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 14 2009

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 14 2009

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 14 2009

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 14 2009

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 10-30 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 14 2009

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 14 2009

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 14 2009