unesp- guaratinguetá o.c. winter 1,3, r. de la reza 2, r.c. domingos 3, l.a.g. boldrin 1, c....

UNESP-Guaratinguetá

O.C. Winter1,3, R. de la Reza2, R.C. Domingos3, L.A.G. Boldrin1, C. Chavero2

1 – Grupo de Dinâmica Orbital & Planetologia – UNESP – Guaratinguetá2 - Observatório Nacional – Rio de Janeiro3 – INPE – São José dos Campos

The Contribution of Planetary Migration to the Metallicity of the Star


METALLICITIES OF STARS WITH PLANETS

STRONG STATISTICS - Planet host stars are in average overmetallic by 0.2 dex compared to stars without detected planets (Gonzales, 2003; Santos et al., 2001, etc)

TWO MAIN SCENARIOS

1) PRIMORDIAL - Stars with planets born in overmetallic clouds. That means stars are overmetallic from their centers to their surfaces.

2) ACCRETION - Stars and planets are formed with the same metallicity but during the epoch of planetary formation the star's surfaces are enriched by the accretion of metal rich matter from their disks. Stars are then overmetallic on their surfaces.


DISCUSSION

The first scenario will mean that interstellar matter was or is, very inhomogeneous as its metallicity is concerned. (difficult to prove).

A first tentative to try to find overmetallic stars in star formation regions with weak T tauri stars with ages less than 9 Myr (planetary formation epoch) as Lupus, Chamaleonis and Corona Australis resulted in only solar abundances for all them (James et al. 2005).

Here, we study the conditions for the second mentioned mechanism:

Star's Metallic Contamination


Any study of star's metallic contamination has to consider the following questions:

a) How is produced the bombarding of the star´s photospheres by metallic rich solid particles;

b) The evolution and size of the stellar convective layers;

The particles must be metal rich and deficient in H and He. This could be the case of several types of planetesimals sizes.

Hot and massive main sequence stars have small convective layers, then any extra metallicity produced by the injections of particles will be maintained against dilution produced by the mixture with star's internal material.

Contrary, cool and less massive stars, have larger convective layers. In these stars is expected that the extra metallic injection will be rapidly diluted.

Therefore, it is expected that only hot stars show this effect.


We must also consider that stars born with larger convective layers and that have only near 30 Myr, the convective layers attain their stability with a minimum configuration.

In de la Reza et al. (2004) was found what could be the first evidence of the presence of a contamination or accretion mechanism in young stars.

Measurements of the metallicity of two stellar asssociations with ages 20 and 30 Myr showed that in fact, hot G stars have larger Fe abundances than the cool and less massive K types stars (with a convective layer ten times smaller !) belonging to these associations.


The Contribution of Planetary Migration to the Metallicity of the Star


Numerical Simulations

Main Parameters:

# planetesimal disc of 1000 massless particlese=0 ; 1.0 < a < 4.0 A.U.

# M_star = M_sun

# M_Planet = M_Jupiter , eccentricity = 0, 0.1, ..., 0.5

# Planet's Migration: 5 => 0.01 A.U. , timescale = 10², 10³, ... (yrs)

Main Outputs:% collision with the star% collision with the planet% ejection (> 50 A.U.)


e_planet = 0 ; t = 10^6 years

e

a/ap


e_planet = 0.1 ; t = 10^6 years

e

a/ap



e

a/ap


Velocity of Migration


Velocity of Migration

}}{

{

Gas

Planetesimal


Alternative Possibilities

Smaller Planet => less massive disc

Shorter Migration => less massive disc


Thanks for your

attention.

unesp- guaratinguetá o.c. winter 1,3, r. de la reza 2, r.c. domingos 3, l.a.g. boldrin 1, c....

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