Supernovae and Gamma-Ray Bursts

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

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.

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

23:59:59.996 He → C, O H → He C → Ne, Na, Mg, O C → Ne, Na, Mg, O 12 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

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 23:59:59.99997 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!!

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.

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

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

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

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

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