Pair Instability Supernovae Lecture 19 Pair Instability Supernovae and Population III

Mass Loss in Very Massive Primordial Stars Negligible line-driven winds (mass loss ~ metallicity1/2) (Kudritzki 2002) No opacity-driven pulsations (no metals) Continuum-driven winds likely small contribution Epsilon mechanism inefficient in metal-free stars below ~1000 M (Baraffe, Heger & Woosley 2000) from pulsational analysis we estimate upper limits: 120 solar masses: < 0.2 % 300 solar masses: < 3.0 % 500 solar masses: < 5.0 % 1000 solar masses: < 12.0 % during central hydrogen burning Red Super Giant pulsations could lead to significant mass loss during helium burning for stars above ~500 M

Can very massive stars retain their mass even today? The Pistol Star Galactic star Extremely high mass loss rate Initial mass: 150 (?) Will die as much less massive object

Eta Carina Thought to be over 100 solar masses Giant eruption in 1843. Supernova-like energy release. 2nd rightest star in the sky. V = -0.8 12 - 20 solar masses of material were ejected in less than a decade. 8000 light years distant. Doubled its brightness in 1998- 1999. Now visble V = 4.7.

(M> 40 solar masses) Pair instability Barkat, Rakavy and Sack (1967) (M> 40 solar masses) Helium core mostly convective and radiation a large part of the total pressure.~ 4/3. Contracts and heats up after helium burning. Ignites carbon burning radiatively Above 1 x 109 K, pair neutrinos accelerate evolution. Contraction continues. Pair concentration increases. Energy goes into rest mass of pairs rather than increasing pressure,  < 4/3. Contraction accelerates. Oxygen and (off-center) carbon burn explosively liberating a large amount of energy. At higher mass silicon burns to 56Ni The star completely, or partially explodes

Nomoto and Hasimoto (1986) Helium stars

Pair-Instability Supernovae Many studies in literature since more than 3 decades, e.g., Rakavey, Shaviv, & Zinamon (1967) Bond, Anett, & Carr (1984) Glatzel, Fricke, & El Eid (1985) Woosley (1986) Some recent calculations: Umeda & Nomoto 2001 Heger & Woosley 2002 Pulsational Pair Supernovae Pair instability Supernovae Rotation reduces these mass limits! Mass loss alters them. Black holes

Ejected “metals”

Elemental production factor in a Pop III 15 M star primordial initial composition

Elemental production factor in a 25 M star primordial initial composition

Elemental production factor in a 35 M star  fallback primordial initial composition

“Standard model”, 1.2 B, = 1.35, mix = 0.1, 10 - 100 solar masses

Best fit, 0.9 B, = 1.35, mix = 0.0158, 10 - 100 solar masses

28 metal poor stars in the Milky Way Galaxy Lai et al. 2008, ApJ, 681, 1524 28 metal poor stars in the Milky Way Galaxy -4 < [Fe/H] < -2; 13 are < -.26 Cr I and II, non-LTE effects; see also Sobeck et al (2007)

Production factor of massive Pop III stars – “standard” mixing included

(Frebel)

Church et al (2009, submitted). Mixing depends on RSG or BSG nature of progenitor and hence rotation and metallicity

Umeda and Nomoto, Nature, 422, 871, (2003)

(Christlieb)

Pair Instability Supernovae Nucleosynthesis from Pair Instability Supernovae Heger and Woosley (2002)

Initial mass: 150M

Initial mass: 150M

Initial mass: 250M

Initial mass: 250M

Big odd-even effect and deficiency of neutron rich isotopes. Star explodes right after helium burning so neutron excess is determined by initial metallicity which is very small.

Production factor of massive and very massive Pop III stars

Shock break-out in pair-instabilty supernovae Kasen and Woosley (2009, in preparation)

Spectrum of shock break-out ( R = RSG, B = BSG)

Light curves of pair instability sueprnovae in their restframe

Compared with a typical SN Ia (red SN 2001el), a Type Iip (blue. SN 1999em) and the hypernova SN 2006gy (green)

Red-shifted light curve of a bright pair-instability SN

Spectra near peak light

Instability Supernovae Pulsational Pair Instability Supernovae

Onset of instability At end of first pulse

After 2nd pulse At final point

Velocity and enclosed mass after second mass ejection - 110 solar mass model (74.6 at explosion)

Light curves of the two outbursts (110 solar mass model)

Absolute R-band magnitudes of the 110 solar mass model compared with obsevations of “hypernova” SN 2006gy. Instabilities will smooth these 1 D calculations. The brighter curve assumed twice the velocity for all ejecta. (7.2 x 1050 erg becomes 2.9 x 1051 erg) Woosley, Blinnikov and Heger (2007, Nature, 450, 390)

238 million light years away