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Structure and Evolution of Stars Lecture 15 Rectified flux + Constant Rectified flux + Constant u. Rev. Astro. Astro...

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Structure and Evolution of Stars Lecture 15

Rectified flux + Constant

Rectified flux + Constant

u. Rev. Astro. Astrophys. 2007.45:177-219. Downloaded from arjournals.annualreviews.org by STEWARD OBSERVATORY on 03/24/08. For personal use only.

12

10

0

15

0

NIV

3500

NIV

3500 4000

OIV

4000

NIII – V

CIII

4500

HeII

4500

HeII

6

4

5000

HeII

5

5000

HeI

8

WN WN4

WN6

WN7

2 WN8

5500

CIII

5500

6000

20

WC CIV

WC5

10 WC6

WC8

WC9

6000

Hell 4686

off-Hell 4686

on-off image

NGC300

3.0 WN WC

2.5

WR22 (WN7ha + 0)

q = MWR / Mo

2.0

WR141 (WN6 + 0)

1.5 WR42 (WC7 + 0)

1.0

WR20a (2 x WN6ha)

WR155 (WN6 + 0)

WR11 (WC8 + 0)

WR47 (WN6 + 0)

0.5 WR30 (WC6 + 0)

0

0.9

1.2

WR151 (WN5 + 0)

1.5

log MWR (M )

1.8

20 R(Sun)

HD 96548 (WN8)

HD 164270 (WC9)

HD 66811 (O4 If)

Figure 5 Comparisons between stellar radii at Rosseland optical depths of 20 ( = R∗ , orange) and 2/3 ( = R2/3 , red ) for HD 66811 (O4 If ), HD 96548 (WR40, WN8), and HD 164270 (WR103, WC9), shown to scale. The primary optical wind line-forming region, 11

12

−3

e3

pe distribution of mall Magellanic Cloud, rge Magellanic Cloud, lky Way (d < 3 kpc) (blue) and WC (green) -Rayet stars, according ellmi, Moffat & rero (2003a,b), akos, Moffat & ela (2001), van der t (2001). Both visual lose WR binaries are d (e.g., only three of MC WC4 stars are binaries according to akos et al. 2001). Rare, mediate WN/C stars cluded in the WN e.

a N

SMC 5

5

0

3

4

5

0

6

WN

b

WO

WC

LMC 30 25

25

20

20

N 15

15

10

10

5

5

0

2

3

4

5

6

7

8

9

0

WN

c N

WO 4

WC

Milky way (d < 3kpc) 15

15

10

10

5

5

0

2

3

4

5

WN

6

7

8

9

0

WO 4

5

6

WC

7

8

9

Figur hahn lution Z = 0 Crosscate w ing oc bols region tails. & Me

Table 15 12.1. Properties of nuclear burning stages in a 15 M! star (from Woosley et al. 2002). burning stage

T (109 K)

ρ (g/cm3 )

fuel

main products

timescale

hydrogen helium carbon neon oxygen silicon

0.035 0.18 0.83 1.6 1.9 3.3

5.8 1.4 × 103 2.4 × 105 7.2 × 106 6.7 × 106 4.3 × 107

H He C Ne O, Mg Si, S

He C, O O, Ne O, Mg Si, S Fe, Ni

1.1 × 107 yr 2.0 × 106 yr 2.0 × 103 yr 0.7 yr 2.6 yr 18 d

Following carbon exhaustion in the centre, the core – which is now composed mostly of O and Ne – contracts on its neutrino-accelerated Kelvin-Helmholtz timescale and carbon burning continues n a convective shell around this core. Several such convective shell-burning episodes can occur in uccession, as shown in Fig. 12.7, their number depending on the mass of the star. The discrete nature f these shell burning events can also produce a discrete (discontinuous) dependence of the final state

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!"#$%&"'()*!#$+)* ,#%&-./0- 1.*"$2* 3445)* 66718)*99)*3:;

Wolf-Rayet (WN11) star in NGC 300 at 2 Mpc distance

Bresolin et al. 2002

The principle of radiatively driven winds

Photons WIND

STAR

totally transferred momentum

OBSERVER

electron

=

nucleus

The photon

is absorbed

and

Figure 2: Principle of radiative line-driving (see text).

reemitted again

r + dr r



v v + dv

ρ

!"#$%&$'"#()**+

complex atomic models for O-stars (Pauldrach et al., 2001)

46

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4 P CYGNI PROFILES

23

Figure 14: Response of theoretical P Cygni profiles to a variation of ion density (line strength) and velocity field. See text.

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ABA:3> ACA:3> %+=-7 7!$<

!!"

MASSIVE STARS IN THE LOCAL GROUP

33

Figure 5 A comparison is shown between the observed mass-loss rates determined by Puls et al. (1996) and that predicted by the empirical fit of de Jager et al. (1988) (openMassey symbols) and the theoretical formalism of Vink et al. (2001) ( filled symbols). Circles denote Galactic

2003