The SIMECA code :modeling the circumstellar environement of Be Stars

Anthony Meilland & Philippe Stee

The SIMECA code

Hydrodynamics :ρ, Vr, VФ, T

Statistical equilibriumn1,…,n7,ne at the LTE

n1,…,n7,ne NLTE(Sobolev escape probabilty)

Line profiles

Intensity mapsIn the lines

Intensity mapsIn the continuum

Spectral Energy Distribution

Input Parameters

Transfer equation In the continuum

Transfer equation In the lines

Transfer equationIn the continuum

Input parameters

-Stellar Radius (can depend on latitude)-Effective Temperature (can depend on latitude)-Distance

-Stellar rotational velocity-Rotation law exponent

-Photospheric density

-Polar and equatorial terminal expansion velocity -Expansion velocity latitudinal variation exponent

-Polar and equatorial mass flux-Mass flux latitudinal variation exponent

-Envelope outer radius

-Inclination angle n

An example : α Arae

ProblemsRotation or expansion?

VΦ >> Vr VΦ ~ Vr

Solution : Interferometry

VΦ >> Vr VΦ ~ Vr

Parameters estimation

Inclination angle :

-Degeneracy problem in spectroscopy -First estimation with critical velocity (Vrot≤Vc) -Estimated with interferometry (envelope flattening)

Equatorial disk extension :

-Vsini and Double peak separation with a chosen rotation law (keplerian)-Direct determination with interferometry

Stellar parameters:

-Distance (not a problem with Gaïa)-Effective temperature and Stellar Radius from the SED fit up to 1μm

Mass flux and expansion velocity parameters (6 parameters) :

-Very difficult to determine-All related to the envelope mass

Envelope mass determinationFrom the IR-Flux

sunenv MM 1110 sunenv MM 1010.4

So, what do we need?

-Blue part of the SED ( at least 2 spectral band less than 1μm)=> Stellar parameters

-Absorption lines => Vsini

-Red part of the SED (at least 1 spectral band over 2μm)=> Envelope Mass

-One or more spectral lines with sufficient spectral resolution (R>10000) =>Disk extension (if we also have the Vsini)