1. Supernovae and Gamma-Ray Bursts

2. Summary of Post-Main-Sequence Evolution of Stars
Supernova
Fusion proceeds; formation of Fe core.
Subsequent ignition of nuclear reactions involving heavier elements
M > 8 Msun
Fusion stops at formation of C,O core.
M < 4 Msun

3. Fusion of Heavier Elements
126C + 42He → 168O + g
168O + 42He → 2010Ne + g
168O + 168O → 2814Si + 42He
Onset of Si burning at T ~ 3x109 K
→ formation of S, Ar, …;
→ formation of 5426Fe and 5626Fe
→ iron core
Final stages of fusion happen extremely rapidly: Si burning lasts only for ~ 2 days.

4. The Life “Clock” of a Massive Star (> 8 Msun)
Let’s compress a massive star’s life into one day…
H → He 12 11 1
Life on the Main Sequence
+ Expansion to Red Giant: 22 h, 24 min.
H burning 10 2 9 3 4 8 7 5 6
H → He
He → C, O 12 11 1 10 2
He burning:
(Horizontal Branch) 1 h, 35 min, 53 s 9 3 4 8 7 5 6

5. 23:59:59.996 He → C, O H → He C → Ne, Na, Mg, O C → Ne, Na, Mg, O12 11 1
C → Ne, Na, Mg, O 10 2 3 9
C burning:
6.99 s 4 8 7 5 6
C → Ne, Na, Mg, O
H → He
He → C, O
Ne → O, Mg
Ne burning:
6 ms
23:59:59.996

6. 23:59:59.99997 The final 0.03 msec!! C → Ne, Na, Mg, O H → He
H → He
Ne → O, Mg
He → C, O
O → Si, S, P
O burning:
3.97 ms
23:59:
C → Ne, Na, Mg, O
H → He
Ne → O, Mg
He → C, O
O → Si, S, P
Si → Fe, Co, Ni
Si burning:
0.03 ms
The final 0.03 msec!!

7. Observations of Supernovae
Total energy output:
DEne ~ 3x1053 erg (~ 100 L0 tlife,0)
DEkin ~ 1051 erg
DEph ~ 1049 erg
Lpk ~ 1043 erg/s ~ 109 L0
~ Lgalaxy!
Supernovae can easily be seen in distant galaxies.

8. Observed with the MDM 1.3 m telescope
SN 2006X in M 100
Observed with the MDM 1.3 m telescope

9. Type I and II Supernovae
Core collapse of a massive star: Type II Supernova
Light curve shapes dominated by delayed energy input due to radioactive decay of 5628Ni
Type II P
Collapse of an accreting White Dwarf exceeding the Chandrasekhar mass limit → Type Ia Supernova.
Type II L
Type I: No hydrogen lines in the spectrum
Type II: Hydrogen lines in the spectrum
Type Ib: He-rich
Type Ic: He-poor

10. The Famous Supernova of 1987: SN 1987A
Unusual type II Supernova in the Large Magellanic Cloud in Feb. 1987
Before
At maximum
Progenitor: Blue supergiant (denser than normal SN II progenitor)
20 M0;
lost ~ 1.4 – 1.6 M0 prior to SN
Evolved from red to blue ~ 40,000 yr prior to SN

11. The Remnant of SN 1987A
Ring due to SN ejecta catching up with pre-SN stellar wind; also observable in X-rays.
vej ~ 0.1 c
Neutrinos from SN1987 have been observed by Kamiokande (Japan)
Escape before shock becomes opaque to neutrinos → before peak of light curve
provided firm upper limit on ne mass: mne < 16 eV

12. Remnant of SN1978A in X-rays
Color contours: Chandra X-ray image
White contours: HST optical image