1 / 17

Formation of Planets around M & L dwarfs

Doug Lin:. Formation of Planets around M & L dwarfs. D.N.C. Lin University of California with. S. Ida , H. Li, S.L.Li, E. Thommes , I. Dobbs-Dixon, S.T. Lee,P. Garaud, M. Nagasawa. AAS Washington

nico
Download Presentation

Formation of Planets around M & L dwarfs

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Doug Lin: Formation of Planets around M & L dwarfs D.N.C. Lin University of California with S. Ida, H. Li, S.L.Li, E. Thommes, I. Dobbs-Dixon,S.T. Lee,P. Garaud, M. Nagasawa AAS Washington Jan 11th, 2006 17 slides

  2. Disk properties Calvet Hillenbrand • 1 Disk life time is independent of M*:similar available time • 2 Disk accretion rate varies as M*2: Less gas content • 3 Disk heavy element mass varies as M*1-2?Less metals

  3. Preferred locations Meteorites: Dry, chondrules & CAI’s Enhancement factor > 4 Icy moons

  4. Stellar mass dependence T(snow line) ~160K, L ~ M2 a(snow line) ~ (L)1/2/T2 ~2.7(M*/Mo) AU Vk(snow)~(M/a)1/2 ~Const ;H/a ~Const Similar aspect ratio and Keplerian speed! But shorter time scales (a/Vk) for lower M* Water-rich planets form near low-mass stars

  5. From planetesimals to embryos Feeding zones: D ~ 10 rHill Isolation mass: Misolation ~S1.5 a3M*-1/2 Initial growth: (runaway) Shorter growth time scale at the snow line

  6. M* dependence Scaling disk models with M*: a)Solar system: Minimum-mass nebula b)Other stars: S(a) = SSN(a) hd where hd = (M*/Msun)0,1,2 c)Embryos with Mp>Mearth are formed outside snow line Importance of snow line: Interior to it: growth limit due to isolation Exterior to it: long growth time scale Outside the snow line: Misolation ~1.3(a/1AU)3/4(M*/Mo)3/2Mearthless massive embryos tembryos ~0.033(a/1AU)59/20(M*/Mo)-16/15Myrlonger growth time Can form >3Mearth embryos outside 5AU within 10Myr

  7. Disk-planet tidal interactions type-I migration type-II migration Lin & Papaloizou (1985),.... Goldreich & Tremaine (1979), Ward (1986, 1997), Tanaka et al. (2002) planet’s perturbation viscous diffusion disk torque imbalance viscous disk accretion

  8. Low-mass embryo (10 Mearth) Cooler and invisic disks

  9. (Mass) growth vs (orbital) decay Embryos’ migration time scale Outer embryos are better preserved only after significant gas depletion Critical-mass core:Mp=5Mearth Loss due to Type I migration

  10. Flow into the Roche potential Equation of motion: Bondi radius (Rb=GMp /cs2) Hill’s radius (Rh=(Mp/3M* )1/3 a) Disk thickness (H=csa/Vk) Rb/ Rh =31/3(Mp /M*)2/3(a/H)2 decreases with M* If Rb> Rh, , a large decline in r (+ve r gradient) would be needed to overcome the tidal barrier. A small r at the Hill’s radius would quench the accretion flow.

  11. Reduction in the accretion rate Growth time scales: Embryos’ emergence time scale: ~ 0.033(a/1AU)59/20(M*/Mo)-16/15Myr KH cooling/contraction of the envelope: ~102-4 (Mp/Mearth)-(3-4)Myr Uninhibited Bondi accretion: ~(H/a)4(M*2/MpMd )/Wk ~102-3yr(MJ/Mp) Uninhibited accretion from the disk: ~Mp/(dM/dt)~ 103-4yr(Mp/MJ) Reduction due to Hill’s barrier: >tdisk depletion Tidal barriers suppress the emergence of gas giants around low-mass stars

  12. Gap formation & type II migration Viscous and thermal conditions Lower limiting mass for gas giants around low-mass stars Neptune-mass planets can open up gaps and migrate close to the stars

  13. Hot Neptunes around low-M* stars Radial extent is determined by Vk > Vescape

  14. Migration-free sweeping secular resonances Resonant secular perturbation Mdisk ~Mp (Ward, Ida, Nagasawa) Ups And Transitional disks

  15. Bode’s law: dynamically porous terrestrial planets orbits with low eccentricities with wide separation Dynamical shake up (Nagasawa, Thommes)

  16. Formation of water worlds Jupiter-Saturn secular interaction & multiple extrasolar systems Sweeping secular resonance may be more intense in low-mass stars. But the absence of gas or ice giants would leave behind dynamically-hot earth-mass objects

  17. Snow line is important for the retention of heavy. Around • low-mass stars, planets with mass greater than that of the • earth are formed outside the snow line. • 2. Planet-disk interaction can lead to depletion of first • generation planetesimals, especially around low-mass stars • Self regulation led to the stellar accretion of most • heavy elements, the late emergence of planets, and • perhaps the inner holes inferred from SED’s. • 4. Around low-mass stars, gas accretion rate onto proto gas • giants is also suppressed by a tidal barrier. • 5. Neptune-mass embryos can open up gaps and migrate • to the stellar proximity. • Residual planetesimals may have modest eccentricities. • 7 There will be a desert of gas giants and an oasis of terrestrial • planets, including short-period water worlds around dwarfs. Summary

More Related