-+

Hydrogen Lines in DA White Dwarfs: Improved Stark Broadening

E

Pier-Emmanuel Tremblay & Pierre BergeronUniversité de Montréal

Hydrogen-line (DA) white dwarfs

Spectroscopic Technique : Bergeron et al. (1992)

Photosphere at 20,000 K

Mihalas, Hummer & Däppen 1988Occupation probability formalism

Mihalas, Hummer & Däppen 1988Occupation probability formalism

charged - neutral

T=10,000 K T=20,000 K

W

WD0205+250

"old models" priorto 1992

Mike Seaton (1990) : MHD88 effects should also be included in line profiles calculations.

Bergeron (1993) : ad-hoc parameter, used in all codes (TLUSTY)

VCS βcritx2

Stark Broadening - Hydrogen

-

+

+

+

+

+

+

Constant Electric FieldLinear Stark Effect

Microfield Distribution

β=E/Eo

P(β)dβ

MHD88 : HoltsmarkNayfonov (1999) : Hooper

H

e-

v

r=Rdebye

r=Rmin

Ψ(H)

Ψ(e)

ρ

Vidal, Cooper & Smith (1973)Lemke (1997)

Constant Electric FieldLinear Stark Effect

t

n=1

n=2

n=3

n=4n=5

Non-adiabatic quantum calculations

electronic collisionsno-quenching

Hydrogen Atom : V(r) V(r) + qEz

V(z)

z

V(z)

z Saddle point

ΔE

Energy of Nth level

ΔEBound state Free State

Mihalas, Hummer & Däppen 1988Occupation probability formalism

βcrit value not arbitrary!

Βcrit

} electronic collisions

Seaton (1990)

Low Fields

High Fields

Seaton (1990) : first non-ideal profiles using approximate electronic broadening profiles

Bergeron (1993) : ad-hoc parameter.

This work•Vidal, Cooper & Smith (1973) electron broadening theory.

•Non-ideal correction for proton perturbations (MHD 88, Seaton 90).

This work•Non-ideal correction for electron perturbations (MHD 88).•It accounts for about 10% of the non-ideal effects.

Consistent implementation of the MHD88 Theory.

T=10,000 KLog Ne =17

VCS This Work M. Seaton(Lemke 1997)

Wiese et al. (1972)

0.55 M

0.7 M

0.7 M

0.55 M

0.55 M

0.7 M

0.7 M

0.55 M

ΔTeff =+100 K Δlog g = +0.06

GD71 HZ43

This workVCS βcritx2

Independent constraints

40 Eri B

Conclusion

• Spectroscopic technique (Bergeron et al. 1992).

• Current model atmospheres use MHD88 EOS and VCS Stark broadening profiles (Lemke 1997 tables)

• Here we add MHD88 inside the VCS broadening theory in a consistent way for the first time.

• We are currently looking at further implications at low and high Teff, UV lines and DO white dwarfs.