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
!"#$%&'())*
!"#$%&'()*(+%',-.#&(#/#&0+1+2(3)-(+-#.+ 45(+6%'.71#/-(! 86%%1+ 9:(+%',-.6$ ;-'&.(<1/=+
!"#$%&"'()*!#$+)* ,#%&-./0- 1.*"$2* 3445)* 66718)*99)*3:;
Wolf-Rayet (WN11) star in NGC 300 at 2 Mpc distance
Bresolin et al. 2002
The principle of radiatively driven winds
Photons WIND
STAR
totally transferred momentum
OBSERVER
electron
=
nucleus
The photon
is absorbed
and
Figure 2: Principle of radiative line-driving (see text).
reemitted again
r + dr r
Lν
v v + dv
ρ
!"#$%&$'"#()**+
complex atomic models for O-stars (Pauldrach et al., 2001)
46
!"#$%&'()*+,'-%*$.(-/'0111
4 P CYGNI PROFILES
23
Figure 14: Response of theoretical P Cygni profiles to a variation of ion density (line strength) and velocity field. See text.
%+=->?7@
!!"
ABA:3> ACA:3> %+=-7 7!$<
!!"
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