Download Stellar Life Cycle

Stellar Life Cycle
1.  Birth [Molecular Clouds, T Tauri stars]
2.  Middle Age [Main sequence, H>He fusion]
3.  Giant-Supergiant [Shell burning, high z fusion]
4.  Death [low mass-planetary nebula>white dwarf]
[high mass- Supernova>pulsar, black hole]
Stellar Death
Low mass
He or C,O core
Planetary nebula
Remnant < 1.4 Msun
White Dwarf
Size
~ Earth
Density(g/cm3) 106
High mass > 8Msun
Fe core
Supernova
Remnant < 3Msun
Neutron star
> 3Msun
Black Hole
~15 km
1014
MagField(G)
104-108
1012
Rotation
minutes
<sec
Pressure
e- degeneracy
neutron degeneracy
0
infinity
?
<<sec
none
WDs have no fusion; cool at constant R
tracks from MS to WDs for different masses
high mass
low mass
R
black dwarfs
Low Mass Death - a White Dwarf
degeneracy
Pauli exclusion principle: no 2 electrons can be in the same
state (position & momentum)
as T increases, more states available P ∝ T
at high density, collisions restricted P ∝ ρ
if all states full, gas is degenerate
as star contracts, ρ increases so becomes degenerate
as T increases, degeneracy is lifted
when He - C fusion starts, core is degenerate
He flash removes degeneracy
WDs are totally degenerate
up to 1. 4 M¤ degeneracy pressure stops the collapse
White Dwarf M-R Relation
P ∝ ρ5/3
ρ ∝ M/R3
hydro-equil
P ∝ M2/R4
M2/R4 ∝ M5/3/ R5
M1/3 ∝ 1/R
R ∝ 1/M1/3
1175 WDs from SDSS
Scatter at low end due to thickness of atm
which depends on T
WDs from SDSS
DB WDs
DZ WDs
Stellar Death
Low mass
He or C,O core
Planetary nebula
Remnant < 1.4 Msun
White Dwarf
Size
~ Earth
Density(g/cm3) 106
High mass
Fe core
Supernova
Remnant < 3Msun
Neutron star
> 3Msun
Black Hole
~15 km
1014
MagField(G)
104-108
1012
Rotation
minutes
<sec
Pressure
e- degeneracy
neutron degeneracy
0
infinity
?
<<sec
none
Supernovae
a (WD binary), b, c
massive single stars)
massive single
stars
Type I - no H, found in all galaxies
Type II - H, only in spiral arms (massive stars)
Type Ia SN lc’s and spectra - obs and models
4 Major types of SN:
Type I – no H
•  Ia – collapsing WD (from binary)
•  Ib – Fe core collapse no H
•  Ic – Fe core collapse, no H, no He
Type II – Fe core collapse with H
Famous Supernovae
Naked eye in Milky Way:
1054 Crab
1572 Tycho - type Ia
1604 Kepler - type Ia
In LMC
SN 1987a Feb 1987 neutrino burst seen
γ+e
e + neutrino + anti-neutrino
γ+γ
neutrino + anti-neutrino
We are overdue ~ 1/20 yrs/galaxy
Stellar Death
Low mass
He or C,O core
Planetary nebula
Remnant < 1.4 Msun
White Dwarf
Size
~ Earth
Density(g/cm3) 106
High mass
Fe core
Supernova
Remnant < 3Msun
Neutron star
> 3Msun
Black Hole
~15 km
1014
MagField(G)
104-108
1012
Rotation
minutes
<sec
Pressure
e- degeneracy
neutron degeneracy
0
infinity
?
<<sec
none
Neutron stars=pulsars
found in radio 1967
density=1014g/cm3
mass < 3M¤
R ~ 10 km
B ~ 1012G
pulse 1-1000/sec
LGM pulsating neutron star rotating neutron star
Black Body = thermal (Planck Function)
Synchrotron = non-thermal (relativistic)
νc = eB/2πme
Flux
Wavelength
Black Holes (R=0, ρ = ∞)
for object in orbit around mass M at distance R:
escape velocity = (2GM/R)1/2
for light, v = c c = (2GM/R)1/2
c2 = 2GM/R
Rs = 2GM/c2
Schwarzschild radius
Rs is event horizon
1M¤→ Rs = 3km, 10M¤→ Rs = 30km, 150kg→ Rs = 10-23cm
Earth has Newtonian Physics; BHs have Relativistic Physics
if you ride into a BH → you go in
if you watch someone ride in → they stay at Rs
Proof of Black Hole:
1)  Single-lined spectroscopic binary
Kepler’s Law M1+M2=P(K1+K2)3 /2πGsin3i ~ 20M¤
spectral type M1 shows M1 ~ 10M¤
M2 ~ 10M¤ but invisible
2)  strong X-ray emission 1036-38 ergs/s
Her X-1 in opt & X-ray
X-ray sources
Massive X-ray Binaries (MXRBs)
Name
P (days)
Vela X-1
9
Cen X-3
2.1
Cyg X-1
5.6
Sp
q
B0Ia 12
O7III 17
O9.7I 3
Mx
1.9
1
6
Low Mass X-ray Binaries (LMXRBs)
Name
1626-67
P(hrs)
0.7
Sec
Mx
WD
Cyg X-3 4.8
IR
Her X-1 40.8
B-F
1
long
E >1051ergs
short
Binary Evolution: Roche equipotential surfaces
rc /A = 0.38 + 0.2 log q [0.3 < q < 2]
A=separation between centers of stars
rc /A = 0.46 (q/1+q)1/3 [0<q<0.3]
q=M2/M1
20M¤ + 8M¤ P=5 days
t = 1 million yrs
transfers 15M¤ in 30,000yrs
If non-conservative transfer
5M¤ + 23M¤ P=11 days
P= 13 days t=10 million yrs
X-ray binary for 10,000 yrs
P = 4 hrs