The Structure of Winds in AGB Stars Moshe Elitzur(Kentucky) Željko Ivezić(Princeton) Dejan...

The Structure of Winds in AGB Stars

Moshe Elitzur (Kentucky)

Željko Ivezić (Princeton)

Dejan Vinković (Kentucky)

MNRAS 327, 403 (2001)

Once the sonic point is crossed…

• Radiation pressure decouples the outflow from the wind origin

• Same grains same wind structure however grains were formed!

gravityP

~dragP

~P radrad

wy

dyPQ

22

21

Wind Problem

• Radiation pressure

• Gas drag

• Gravity

tcosA2

1)y()y(

y

P

dy

dw2

22

wln)(

)w()(

)w)((

w)1(4wy1

11P

3

2/12/12

21

2/32/33122

2

11

Physical Domain

FcL

vM

<>F = (Q*/QV) V (1 + V)-0.36

Q* = <Q>B(T*)

cL

vM

Fudge factor –task for full models

Scaling

Away from boundaries, wind structure fully controlled by

Velocity Profile

Scale of v set by

222

22d

H

d cm10nn

k

r'r

1vv

V < 1: k = 2/3 (drift)

V > 1: k 0.4 (reddening)

K. Young 1995:

• v independent of L

• Mv 3.3

Drift!

Miras, low :M

Radiation pressure:

• v L1/2

• v independent of M

5.1v

3 )1(MAv

Drift Effect on Outflow

L/M 3/4V

222A

Same ndd/nH for C- and O-stars!

Drift+Reddening effect on v

• Lower – decoupling; v

• Higher – quenching; v

M

M

14/14max

14/34

6max

kmsL20v

yrML102)v(M

v = 18

• Shape V

• Flux level

SED Analysis

Zubko & Elitzur ’00

v = 0.83

Solutions by DUSTY http://www.pa.uky.edu/~moshe/dusty/

+ distance L

• L + v , 22M

W Hya

Thermal H2O Lines

• W Hya (ZE ‘00):

21 lines fitted H2O abundances

• VY CMa (Harwit & Bergin ‘02):

Same line ratios!

Hofmann et al ‘01

Vinković ‘02

Conclusions

• The “standard model” works

• Single variable –

• Dust drift – major ingredient

• Minimal = ?

22 ~ 1; why?

M

dFF1

dFF

Fc1

dFc1

dtdv

F

F

steady state: dt = (1/v)dr

F

F2

c12

dcL

dvM

drFrvdvr