Unkown stellar mass loss at low metallicity
Download
1 / 27

Unkown stellar mass loss at low metallicity - PowerPoint PPT Presentation


  • 102 Views
  • Uploaded on

Unkown stellar mass loss at low metallicity. Henny Lamers Astronomical Institute and SRON Laboratory for Space Research Utrecht University. Topics to be discussed. Predictions of properties of “normal” winds (Z~solar) and comparison with observations

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Unkown stellar mass loss at low metallicity' - hilda


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.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Unkown stellar mass loss at low metallicity

Unkown stellar mass loss at low metallicity

Henny Lamers

Astronomical Institute and

SRON Laboratory for Space Research

Utrecht University


Topics to be discussed
Topics to be discussed

Predictions of properties of “normal” winds (Z~solar)

and comparison with observations

Predicted properties of low Z winds (Z~10-4 solar)

Extremely no Z winds (H and He only)


Net force in wind: gnet = - gN + ge + glines > 0

Gravity : gN = GM / R2

Rad pressure by electrons : ge = σe L / 4 π R2 c = Γe gN

Rad pressure by lines: gl = ge M(t)

Force multiplier: M(t) = k t-α (ne/W)δ

Solar Z : k ~ 1/30 α ~ 0.6 δ ~ 0.1

Castor, Abbott & Klein 1975, CAK


Predictions scaling laws
Predictions: scaling laws

Castor, Abbott, Klein 1975

v∞ ~ (2 to 3)v esc ~ √ (M/R)

Mdot ~ L 1/α M (α-1)/α


Predictions scaling laws1
Predictions: scaling laws

Castor, Abbott, Klein 1975

v∞ ~ (2 to 3)v esc ~ √ (M/R)

Mdot ~ L 1/α M (α-1)/α

Kudritzki et al 1989

П≡ Mdotv∞√ R ~L 1/α M 0.5-(1-α)/α ~ L 1/α

П = Modified wind momentum


Predicted mass loss rates
Predicted mass loss rates

Vink et al. 2000


Modified wind momentum l
Modified wind momentum П↔ L

predictions

Log П

observations

Vink et al. 2000


New study with improved mass loss rates
New study with improved mass loss rates

Galactic

stars

Markova et al. 2004


Problem
Problem:

Some stars with very similar stellar parameters show a large difference in mass loss rate and wind properties !!


Tale of two stars
“Tale of two stars”

AV 83 AV 69

Type O7 Iaf+ O7.5 III

L/Lsun 3.5 105 4.1 105

Teff 32800 33900

R/Rsun 18.5 18.6

He/H 0.2 0.1

C/N 0.15 15

Hillier et al. 2003



AV 83 AV 69

Mdot 7 10-7 9 10-7

V∞ 940 1800

β 2.0 1.0

fclump 0.1 1

ROTATION !!!

Hillier et al. 2003


  • Effects of rotation

  • Flattening

  • 2. Gravity = f( θ)

  • 3. Teff = f(θ )

  • 4. Mdot = f(θ)

  • 5. Vwind = f(θ)

  • 6. Spect type = f(sin i)

Meynet & Maeder 2002




Predictions for line driven winds
Predictions for line driven winds

10-2 < Z/Zsun <10+1

Mdot ~ Z 0.85

Vink et al. 2001


Observations predictions
Observations ↔ Predictions

LMC SMC

Vink et al. 2001


The problem of the winds of low luminosity smc stars
The problem of the winds of low luminosity SMC stars

Black = Gal

Red = LMC

Blue = SMC

П↔L relation breaks down at log L < 5.3 !!

Martins et al. 2004



Predictions at low z parameters k vary with distance
Predictions at low Zparameters k, α, δ vary with distance

Z/Zsun

1.0

0.2

10-2

10-3

10-4

П

Kudritzki 2002


Very low z stars only have winds when they are close to eddington limit
Very low Z stars only have winds when they are close to Eddington limit !

grad = ge + glines > gN at some depth

glines = M(t) ge

Mmax ≈ 2000 Z/Zsun + M(H,He) from atomic physics

So maximumradiation pressure is

gradmax = (1+Mmax) ge = (1+Mmax) Γe gN > gN

Γe > (1+Mmax)-1


Dependence of mass loss on e
Dependence of mass loss on Eddington limit !Γe

← Mdot ≈ 10-8

Msun/yr

Kudritzki 2002


Zero metallicity stars
Zero metallicity stars Eddington limit !

1. Radiation pressure only due to H and He lines

2. H lines alone are never strong enough

3. HeII lines can produce grad-gN >0 if

level populations are just right

but only in very small region of atmosphere.

Krticka & Kubat, 2005


g Eddington limit !eff > 0 only in very

small zone

Zero metallicity stars have NO line driven winds !!

Krticka & Kubat 2005


Conclusions
Conclusions Eddington limit !

A: 10-3 < Z/Zsun < 10 : Mdot ~ Z0.85

but : Mdot depends on (fast) rotation

B: 10-4 < Z/Zsun < 10-3 : Mdot ~only for large Γe

Γe > (1+Mmax)-1

Mmax ≈ 2000 Z/Zsun

C: Z/Zsun=0 : no line driven wind,

Mdot < 10 -10 Msun/yr


That s all
That’s all ! Eddington limit !


ad