Insights from recent surveys Gaspard Duchêne UC Berkeley Obs Grenoble NASAJPLCaltech Planets in multiple systems LucasFilm Ltd They must exist Planets in multiple systems ID: 654902
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Slide1
Planet formation and stellar multiplicityInsights from recent surveys
Gaspard Duchêne(UC Berkeley, Obs. Grenoble)
© NASA/JPL/CaltechSlide2
Planets in multiple systems?
©
LucasFilm Ltd.
They must exist!Slide3
Planets in multiple systems!One of the pulsar planets is circumbinaryFirst planets in Main Sequence binary systems reported as early as 1997
(Butler et al.)And now MS circumbinary planets…
© NASA
© Greg Bacon –
STScI
/NASA
PSR 1620-26
Kepler
16Slide4
Some open questionsDo planets form in multiple systems?
YES !In a remarkable diversity of systems!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?
Let’s summarize the empirical evidence…Slide5
Schematics of the problem…The early phases of planet formation occur in a circumstellar disk within a few Myr
What is the influence of a stellar companion?Dynamical truncation, but then what?Slide6
Stellar multiplicity~50% of solar-type stars have a stellar companion
Most companions are on close orbits (<100 AU)Even higher frequency for PMS objects!
Far from a
marginal phenomenon !
Raghavan
et al. (2010)Slide7
Protoplanetary disksPlanet-forming disks have sizes ≥ 100 AU
Only a small fraction of the mass resides within ~10 AU, where planets presumably form
Andrews & Williams (2007)
Importance of outer mass reservoir that
can be most affected by a companion
SMASlide8
OutlineThe basics of stellar multiplicity and disksMultiple stars and …
Protoplanetary disks (initial conditions)Debris disks (early stages)Planetary systems (mature systems)
Back to the big pictureSlide9
Primordial disks in binariesBoth stars have a disk
in most casesDisks around primariesare more massivetend to survive longer (?)
Primaries offer better
grounds to form planets
Harris et al. (2012)
SMASlide10
Primordial disks in binariesDisks are much rarer in tight binaries (≤ 40 AU) than in wide ones or around single stars
Clearing during formation?Fast dissipation?No replenishment?Remaining disks are
long-lived (~ 5 Myr)
Kraus et al. (2012)
Taurus-
Auriga
(~1-3Myr)
SpitzerSlide11
Total disk massLimited mass reservoir in tight binaries
Or are compact disks massive and optically thick?No strong dependence on mass ratio
Harris et al.(2012)
Circumbinary
disks
Taurus
SMASlide12
Inner regions propertiesWhen present in binary systems, disks have similar properties in the innermost region
Only the disk surface within < 1AU of the star
Pascucci et al. (2008)
Silicate feature
NIR colors
Cieza
et al. (2009)
disk
larger grain size
SpitzerSlide13
Missing pieces in the picture…The presumed planet-forming region (3-20AU) is not probed by either (sub)mm or NIR
Need to probe the FIR!What about the gas?99% of the mass…
10μm
1.3mm
7
0μm
~250 young stars,
incl
.
106 in Taurus
PI: Bill Dent
Pinte
et al. (2008)
IM
Lup
, ~1M
, R
out
=400AU
Spitzer
SMASlide14
The planet-forming regionNeither the FIR continuum nor the [OI]63 line (main cooling line) depend on separation
No influence of stellar companions
C. Howard et al. (in prep)
circumbinary
Taurus
submm
FIR
cont
[OI]63 line
HerschelSlide15
Protoplanetary disks: summaryDisks in primaries are more auspicious to planet formation than those of secondaries
Outer disk regions are severely depleted in tight binaries (separation < ~100 AU)Lower total disk mass? Shorter lifetime?Planet-forming region is apparently unaffected by the presence of a companionSlide16
OutlineThe basics of stellar multiplicity and disksMultiple stars and …
Protoplanetary disks (initial conditions)Debris disks (early stages)Planetary systems (mature systems)Back to the big pictureSlide17
Debris disks in binariesBinaries among known debris disks: 15-25%
Mannings & Barlow (1998), Plavchan et al. (2009)But 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) Situation needs clarification…Slide18
Debris disks: separation trendKnown debris disks have few companions in the 1-100 AU range (bias?)
© Tim Pyle – SSC/NASA
Trilling et al. (2006)
Rodriguez
& Zuckerman (2012)
113 AFGK stars
63 AF stars
IRAS / ISO
SpitzerSlide19
Debris disks: the Herschel viewAn unbiased volume-limited survey is needed to draw a robust statistical picture
DEBRIS survey (PI: Brenda Matthews)~450 targets, A through M stars (~90 per Sp.T. class)Unbiased sample Uniform observing strategySlide20
Debris disks: the Herschel viewTo complement the Herschel observations, we are gathering a catalog of stellar companionsLiterature/catalog searchesLick Adaptive Optics survey (200+ targets)
D. Rodriguez
et al. (in prep)Slide21
Debris disks: the Herschel viewDebris disks are less frequent in binaries13.7%
vs 22.6 % for the whole sampleCompanions in the 1-1000 AU are particularly disruptive (true for all spectral types)
D. Rodriguez
et al. (in prep)
HerschelSlide22
OutlineThe basics of stellar multiplicity and disksMultiple stars and …
Protoplanetary disks (initial conditions)Debris disks (early stages)Planetary systems (mature systems)Back to the big pictureSlide23
Exoplanets in binariesMost planets are found around primariesExceptions: 16
Cyg B, HD 178911 B but few searches around (lower mass) companionsA handful of planets in triple systemsUsually (A-b) – (B-C)
Extreme case: γ
Cep
Planet: a=2 AU, e=0.2Comp: a=20 AU, e=0.4
Raghavan
et al. (2006)
planet
companionSlide24
Exoplanets: multiplicity~33% of known exoplanet hosts are binaries
Slightly lower rate than among singlesBut severe negative selection bias!Possible deficit of planets if separation ≤ 100 AU
Better statistics w/ Kepler?
Eggenberger
et al. (2009)Slide25
Exoplanets: finer dependenciesEarly studies suggested a peculiar trendClose-in planets in binaries are more massive
No trend in larger sample (nor with e)However …
Zucker
& Mazeh
(2002)From Exoplanet
Encyclopedia and Mugrauer & Neuhauser (2009)Slide26
Exoplanets: finer dependenciesPlanets in wide systems are indistinguishable from those around single stars
Planets in tight binaries always have high massNo influence of other
orbital elements (P, e)
Duchêne (2010)Slide27
OutlineThe basics of stellar multiplicity and disksMultiple stars and …
Protoplanetary disks (initial conditions)Debris disks (early stages)Planetary systems (mature systems)Back to the big pictureSlide28
Planet formation in binariesWide binaries (separations beyond ~50-100 AU) have little influence on the overall process
Almost half of all solar-type binaries!Despite truncation, only the inner 10-30 AU matter, provided enough mass is accumulated early onSlide29
Planet formation in binariesTruncation by tighter binaries is severe, but does not prevent planet formation altogether
Many disks disappear early on (or never form?)Few debris disks are foundPlanets are always of high mass
A different path to form planets?
??Slide30
Planet formation in binariesP
lanets are common in tight binaries (< 1-2 AU)Protoplanetary disks offer sound initial conditionsDebris disks show that planetesimals formed from these disks
An “almost normal” formation processSlide31
Planet formation in binaries
Normal
process
Quasi-normal
process
A different process, affecting ~25% of
all solar-type stars (disk fragmentation?)
Raghavan
et al. (2010)
© NASA/JPL/Caltech
©
LucasFilm
Ltd.
© Tim Jones – McDonald Obs.