Pair-instability supernovae

1. Pair-instability supernovae From Woosley et al. (2002, 2007) Woosley Lecture 19

11. Ejected “metals”

12. Ejected “metals”

22. Ejected “metals”

23. 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

24. 8 – 11 M¯: uncertain situation • M < M1' 8 M¯: No C ignition • M > M2' 12 M¯: Full nondegenerate burning • In between: ???? ? • Degenerate off-centre ignition • Possibly O-Ne-(Mg?) white dwarfs (after some additional mass loss) • With sufficient O-Ne core mass: continued burning and core collapse

25. Pair-instability supernovae Pop. III stars, no mass loss • He burning • collapse and energy release • g + g! e+ + e-: G1 < 4/3 • Dynamical collapse, bounce, explosive burning (for M < 260 M¯) • Dynamical collapse directly to black hole (for M > 260 M¯)

26. Possibly observed: SN 2006gy Smith et al. (2007; ApJ 666, 1116)

27. 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

28. 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

29. Helium stars, MHe = 2.2 – 8 Nomoto and Hasimoto (1986; Prog. Part. Nucl. Phys. 17, 267)

30. ¯ ¯ ¯ ¯ ¯ ¯ 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

32. Light curves of pair instability supernovae in their restframe

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

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

35. Pulsational Pair Instability Supernovae

37. Pulsations Woosley et al. (2007; Nature 450, 390)

38. 238 million light years away Smith et al. (2007; ApJ 666, 1116)

39. Smith et al. (2007; ApJ 666, 1116)

40. Onset of instability Woosley et al. (2007; Nature 450, 390)

41. At end of first pulse Woosley et al. (2007; Nature 450, 390)

42. After 2nd pulse Woosley et al. (2007; Nature 450, 390)

43. At final point Woosley et al. (2007; Nature 450, 390)

44. Shock heating Woosley et al. (2007; Nature 450, 390) Velocity and enclosed mass after second mass ejection - 110 solar mass model (74.6 at explosion)

45. 1999 2006 2012 Light curves of the two outbursts (110 solar mass model) Woosley et al. (2007; Nature 450, 390)

46. 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 et al. (2007; Nature 450, 390)