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Line Shapes in Hot Stars Line Shapes in Hot Stars

Line Shapes in Hot Stars - PowerPoint Presentation

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Line Shapes in Hot Stars - PPT Presentation

Hydrodynamics amp Wind MassLoss Rates David Cohen Swarthmore College with Maurice Leutenegger Stan Owocki Rich Townsend Emma Wollman 09 James MacArthur 11 ID: 240870

line porosity wind mass porosity line mass wind loss pup rate consistent factor trend explanation lya xvii clumping clump

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Slide1

Line Shapes in Hot Stars: Hydrodynamics & Wind Mass-Loss Rates

David Cohen

Swarthmore College

with Maurice

Leutenegger

, Stan

Owocki

, Rich Townsend,

Emma

Wollman

(‘09), James MacArthur (‘11)Slide2

 Pup (O4 If)

Capella

(G5 III)

– coronal source – for comparisonSlide3

 PupCapella

Ne X

Ne IX

Fe XVIISlide4

Pupmassive

Capella

low mass

broad, skewed,

blue shiftedunresolvedSlide5

rad-hydro wind simulations: line-driving instabilitySlide6

shock onset at r ~ 1.5 Rstar

V

shock ~ 300 km/s

: T ~ 106 K

hot plasma has low densitySlide7

99% of the wind mass is cold*, partially ionized…x-ray absorbing*typically 20,000 – 30,000 K; maybe better described as “warm”Slide8

photoelectric absorption:continuum opacity in the cold wind componentCNO processed

solar abundanceSlide9

observer on leftisovelocity contours

-0.8vinf

-0.6vinf

-0.2v

inf+0.2vinf+0.6v

inf

+0.8v

infSlide10

observer on leftisovelocity contours

-0.8vinf

-0.6vinf

-0.2v

inf+0.2vinf+0.6v

inf

+0.8v

inf

optical depth contours

t

= 0.3

t

= 1

t

= 3Slide11

opacity

of the

cold wind

componentwind mass-loss ratewind terminal velocity

radius of the starSlide12
Slide13

t=1,2,

8

key parameters:

R

o & t*

j ~

2

for

r

/R

*

> R

o

,

= 0 otherwise

R

o

=1.5

R

o

=3

R

o

=10

=1 contoursSlide14

We fit these x-ray line profile models to each line in the Chandra dataFe XVII

Fe XVIISlide15

And find a best-fit t* and Ro…

Fe XVII

Fe XVII

t

* = 2.0Ro = 1.5 Slide16

…and place confidence limits on these fitted parameter values68, 90, 95% confidence limitsSlide17

z Pup: three emission lines Mg Lya: 8.42 Å

Ne

Lya

: 12.13 Å

O Lya: 18.97 Å

t

* =

1

t

*

=

2

t

*

=

3

Recall: Slide18

atomic opacity of the windCNO

processed

SolarSlide19

Results from the 3 line fits shown previouslySlide20

Fits to 16 lines in the Chandra spectrum of z PupSlide21

Fits to 16 lines in the Chandra spectrum of z PupSlide22

Fits to 16 lines in the Chandra spectrum of z Pup

t

*

(

l) trend consistent with k(l) Slide23

t*(l) trend consistent with k(

l)

M

becomes the free parameter of the fit to the t*(l) trendSlide24

Traditional mass-loss rate: 8.3 X 10-6 Msun

/yr

Our best fit:

3.5 X 10

-6 Msun/yrSlide25

Fe XVIITraditional mass-loss rate: 8.3 X 10

-6

Msun/yr

Our best fit:

3.5 X 10-6 Msun/yrSlide26

Ori: O9.5

e

Ori: B0 Slide27

z Ori (09.7 I): O Lya 18.97 ÅR

o = 1.6 R*

t* = 0.3Slide28

t* quite low: is resonance scattering affecting this line? - Next talk, by M. Leutenegger

Ro

= 1.6 R*t

* = 0.3Slide29

e Ori (B0 Ia): Ne Lya 12.13 Å

R

o = 1.5 R*

t* = 0.6Slide30

HD 93129Aab (O2.5): Mg XII Lya

8.42 Å

Ro

= 1.8 R*t

* = 1.4M-dot ~ 2 X 10-5 Msun/yrV

inf ~ 3200 km/s

M-dot ~ 5 X 10

-6 M

sun/yrSlide31

Multi-wavelength evidence for lower mass-loss rates is emergingSlide32

z

Pup mass-loss rate < 4.2 X 10-6

Msun

/yrSlide33

“Clumping” – or micro-clumping: affects density-squared diagnostics; independent of clump size, just depends on clump density contrast (or filling factor, f )

visualization: R. TownsendSlide34

The key parameter is the porosity length, h

= (

L

3/ℓ

2) = ℓ/

f

But

porosity

is associated

with

optically

thick

clumps, it

acts to reduce the effective opacity of the

wind; it

does

depend on the size scale of the clumps

L

f

=

3

/

L

3Slide35

h =

ℓ/

f

clump size

clump filling factor (<1)

The porosity length,

h

:

Porosity length increasing

Clump size increasing

Slide36

Porosity only affects line profiles if the porosity length (h) exceeds the stellar radiusSlide37

The clumping in 2-D simulations (density shown below) is on quite small scales

Dessart & Owocki 2003, A&A

, 406, L1Slide38

No expectation of porosity from simulationsNatural explanation of line profiles without invoking porosityFinally, to have porosity, you need clumping in the first place, and once you have clumping…you have your factor ~3 reduction in the mass-loss rate Slide39

No expectation of porosity from simulationsNatural explanation of line profiles without invoking porosityFinally, to have porosity, you need clumping in the first place, and once you have clumping…you have your factor ~3 reduction in the mass-loss rate Slide40

No expectation of porosity from simulationsNatural explanation of line profiles without invoking porosityFinally, to have porosity, you need clumping in the first place, and once you have clumping…you have your factor ~3 reduction in the mass-loss rate (for z Pup, anyway)Slide41

f

= 0.1

f

= 0.2

f = 0.05

f

~ 0.1 is indicated by H-alpha, UV, radio free-free analysis Slide42

f

= 0.1

f

= 0.2

f = 0.05

And lack of evidence for porosity…

leads us to suggest visualization in upper left is closest to realitySlide43

conclusionsLine widths consistent with embedded wind shocksSkewed line shapes consistent with photoelectric absorption; magnitude and wavelength trend enable a mass-loss rate measurementConsistent explanation for zeta Pup – M down by factor of 3, no need to invoke porositySlide44

conclusionsLine widths consistent with embedded wind shocksSkewed line shapes consistent with photoelectric absorption; magnitude and wavelength trend enable a mass-loss rate measurementConsistent explanation for zeta Pup – M down by factor of 3, no need to invoke porositySlide45

conclusionsLine widths consistent with embedded wind shocksSkewed line shapes consistent with photoelectric absorption; magnitude and wavelength trend enable a mass-loss rate measurementConsistent explanation for zeta Pup – M down by factor of 3, no need to invoke porositySlide46

conclusionsLine widths consistent with embedded wind shocksSkewed line shapes consistent with photoelectric absorption; magnitude and wavelength trend enable a mass-loss rate measurementConsistent explanation for zeta Pup – M down by factor of 3, no need to invoke porosity