Pinpointing Planets in Circumstellar Disks Mar 2009 Alice Quillen University of Rochester

3 Systems hosting disks with clearings Epsilon Eridani AgeMass Type DistanceRadius of clearing CoKuTau4 1-2 Myr 0.5M  M 140 pc10 AU Epislon Eridani 600 Myr 0.8M  K 3.2 pc~50 AU Fomalhaut 200 Myr 2.1M  A 7.7 pc133 AU Staplefeldt et al. Greaves et al. 97

All extrasolar planets discovered by radial velocity (blue dots), transit (red) and microlensing (yellow) to 31 August Also shows detection limits of forthcoming space- and ground-based instruments. Discovery space for planet detections based on disk/planet interactions Discovery Space More ambitiously in future

Planets in disks Young systems, evolution of early solar systems Disk clearing by planets, Planet disk interactions Historical context for prediction of bodies prior to discovery: -Moonlet predicted in Enke gap from Voyager data (Cuzzi & Scargle ‘85), body then detected Showalter ’91 -Resonant ring in dust with Earth predicted (Jackson & Zook ‘89) then seen in IRAS data (Dermott et al. ‘94) -Neptune’s location predicted by Adams & LeVerrier (1845) then found by Galle (1846)

Transition Disks Estimate of minimum planet mass to open a gap requires an estimate of disk viscosity. Disk viscosity estimate either based on clearing timescale or using study of accretion disks. Mp > 0.1MJ 4 AU 10 AU CoKuTau/4 D’Alessio et al. 05 Wavelength μm

Estimating required planet mass based on gap opening criterion Limit on viscosity based on clearing during lifetime of object on a viscous timescale Or base on estimates for accretion disks

Minimum Gap Opening Planet In an Accretion Disk Edgar et al. 07 radiation accretion, optically thick Gapless disks lack planets

CoKuTau4 is now known to be a binary star ➞ no planet required Are planets no longer required to explain disk clearing in young stellar objects? NO Massive disks exist with clearings that could not have been cleared by photo-evaporation (Alexander, Najita & Strom) Disks are seen in with large gaps, not just deep clearings as was CoKuTau4 --- these are best explained via planet formation and inefficient clearing Kraus & Ireland 08 Extremely empty clearing explained via binary

Dust Capture models and Epsilon Eridani Debris Disk Dust generated via collisions spirals inwards and is trapped in resonance with giant planets Dust source is late stage collisional evolution – Debris Disks Dust rings as signposts of planets Liou & Zook ‘99, Ozernoy et al. ‘01 Vega disk model by Marc Kucher and collaborators Exploring eccentric planet space, Deller & Maddison ‘05 Rich History: Earth’s resonant ring

Capture of drifting dust by mean- motion resonances with planets Signature of Giant planets seen in the Edgeworth-Kuiper Belt (Liou & Zook 1999) Dust integration weighted by lifetime shows that dust particles trapped in resonances dominate the distribution

An early model for the dust ring in the Epsilon Eridani system Particles generated in resonance with an eccentric planet Long resonance lifetimes Different resonances contrived to make clumps Greaves et al.1997

Epsilon Eridani Recent developments Not all clumps are real However clumps are rotating suggesting that there are some clumps in the disk in corotation with a planet Possible 1 or two inner planets in central AU from Radial velocity and proper motion scatter Greaves et al.

Multiple component dust models based on Spitzer SED, imaging and IRS spectra infrared excess + model components Backman et al inner asteroid belts and one outer one

Update on planet scenarios for Epsilon Eridani Sticking planets right next to ring edges is moderately well justified Our model for outer planet is vastly out of date, eccentric planet no longer needed Collisions, migration, multiple planet interactions now key to understanding this system

Lopsided disks, need for planets and the Pericenter glow model Based on asymmetry in asteroid distribution due to Jupiter’s forced eccentricity Proposed to account for asymmetry of HR4796A’s disk (also has a clearing) by Mark Wyatt and collaborators Mass of planet is not constrained Eccentricity and semi-major of planet related but not individually constrained Fomalhaut HR4796A nicmos Schneider et al. ‘99 Staplefeldt et al.

HST image hailed as another signpost of a planetary system but nature of system was poorly constrained

Another model Adam Deller and Sarah Maddison’s resonant capture model account for disk eccentricity but not sharp edge collisions ignored

Fomalhaut’s eccentric ring steep edge profile h z /r ~ eccentric e=0.11 semi-major axis a=133AU collision timescale =1000 orbits based on measured opacity at 24 microns age 200 Myr orbital period 1000yr Kalas et al. 05

Free and forced eccentricity radii give you eccentricity If free eccentricity is zero then the object has the same eccentricity as the forced one ϖ longitude of pericenter e forced e free

Pericenter glow model Collisions cause orbits to be near closed ones. This implies the free eccentricities in the ring are small. The eccentricity of the ring is then the same as the forced eccentricity We require the edge of the disk to be truncated by the planet  We consider models where eccentricity of ring and ring edge are both caused by the planet. Contrast with precessing ring models.

Disk dynamical boundaries For spiral density waves to be driven into a disk (work by Espresate and Lissauer) Collision time must be shorter than libration time  Spiral density waves are not efficiently driven by a planet into Fomalhaut’s disk A different dynamical boundary is required We consider accounting for the disk edge with the chaotic zone near corotation where there is a large change in dynamics We require the removal timescale in the zone to exceed the collisional timescale.

Corotation chaotic zone Mean motion resonances get stronger and closer together near the planet’s corotation region. An object in the overlap region can make close approaches to the planet Width scales with planet mass to 2/7 power (Wisdom)

Chaotic zone boundary and removal within What mass planet will clear out objects inside the chaos zone fast enough that collisions will not fill it in? M p > Neptune Saturn size Neptune size collisionless lifetime

Dynamics at low free eccentricity Expand about the fixed point (the zero free eccentricity orbit) For particle eccentricity equal to the forced eccentricity and low free eccentricity, the corotation resonance cancels  recover the 2/7 law, chaotic zone same width goes to zero near the planet same as for zero eccentricity planet

Velocity dispersion in the disk edge and an upper limit on Planet mass Distance to disk edge set by width of chaos zone Last resonance that doesn’t overlap the corotation zone affects velocity dispersion in the disk edge M p < Saturn Larger masses also would leave structure in ring, and it is featureless

cleared out by perturbations from the planet M p > Neptune nearly closed orbits due to collisions eccentricity of ring equal to that of the planet Assume that the edge of the ring is the boundary of the chaotic zone. Planet can’t be too massive otherwise the edge of the ring would thicken or show structure  M p < Saturn

Neptune < M p < Saturn Semi-major axis 119 AU (16’’ from star) location predicted using chaotic zone as boundary Eccentricity e p ~0.1, same as ring Longitude of periastron same as the ring

Multiple Epoch HST imaging reveals an object bound to the system Planet discovered at 115AU Interpretation rests on chaotic zone boundary Kalas et al periapse

Surprises Object is much much brighter than I predicted Planet itself is not detected. Object detected has colors of star and is ~60 times brighter in optical than a Jupiter mass planet IR observations rule out planets more massive than 3 Jupiters Circum-planetary disk to account for optical flux? Mass of planet is not known. Eugene Chiang’s group suggest a larger planet than I predicted Planet is slightly further away from disk edge than predicted using chaotic zone boundary. Eccentricity of planet and planet disk interaction still yet to be explained. Kalas et al 08

Summary 3 planets predicted –CokuTau4 planet ruled out – (but class of models still probably okay for other systems –Epsilon Eridani outer planet: model is missing key physics and so is out of date –Fomalhaut. Planet location pretty closely predicted New models to create: with multiple planets to interpret disks with large gaps (as inferred from their spectral energy distribution), including HR8799 and Epislon Eridani post discovery view

Tsiganis et al. 05 `Nice’ Model + Epoch of Late Heavy Bombardment Disk of Fomalhaut is cold, not what would be seen for Solar system during epoch of Late Heavy Bombardment Migration of planets in Fomalhaut system is likely

Where is the next planet??