Wolfgang Hillebrandt. Garching. DEISA PRACE Symposium Barcelona May 10 12, 2010

Transcription

1 Modelling Cosmic Explosions Wolfgang Hillebrandt MPI für Astrophysik Garching DEISA PRACE Symposium Barcelona May 10 12, 2010

2 Outline of the talk Supernova types and phenomenology (in brief) Models of core-collapse collapse supernovae (and gravitational waves) Models of thermonuclear supernovae (and supernova cosmology)

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4 Supernova light curves Luminosity (magnitudes) Time (days)

5 Supernova types: what are they? Thermonuclear SNe (Type Ia ) from low-mass stars (<8M ) highly evolved stars (white dwarfs) explosive C and O burning binary systems required complete disruption Core-collapse SNe (all the others) high mass stars (>8M ) large envelopes (still burning) burning due to compression single stars (binaries for SNe Ib/c?) neutron star

6 Core-collapse Supernovae Prototype: Crab nebula with pulsar (constellation Orion) Remnant of a supernova observed in 1054

7 30 Doradus region in the Large Magellanic Cloud (d ~ light years) Supernova 1987A 7:35 UT Blue Supergiant Sanduleak

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9 A few observational facts very bright events: ~ L sun fast expanding ejecta: ~ 10 4 km/s energies: electromagnetic: ~ J kinetic: ~ J neutrinos (SN1987A): ~ J progenitor star distroyed (SN 1987A, SN 1993J,...) compact remnant (as far as we know) Q: How can we model them? A: A problem of multi-d radiation-hydrodynamics!

10 Supernovae from collapsing massive stars:

11 Blue (Super) Giant (Red S-Giant: 100) km Fe-Ni core km 100 < 20 km > Neutron star

12 Energy sources for a core-collapse collapse supernova Gravitational binding energy Formation of a compact object of ~1 solar mass with a radius ~10km E b ~ 3 x (M/M sun ) 2 (R/10km) -1 J

13 Current paradigm: neutrino-driven explosions (discovered through computer simulations by Wilson '82, and first analyzed by Wilson & Bethe '95) But

14 ... does it really work? No explosions (for massive stars, M 10M )! (Buras et al. 2003)

15 Simulations of core collapse supernovae are challenging, because of: a) neutrino transport (fermions, multi-flavor) (semi-transparent region: Boltzmann solver) b) very different time and length scales adaptive mesh refinement (AMR) c) multi-dimensional flow problem

16 Most recent simulations: The range 10 to 15 M sun (Marek, Janka, 2009, 2010) Initial models: 11.2 & 15 M sun (Woosley et al. 2002) Fe cores 2D, Boltzmann neutrino transport Realistic equations of state (Weak) explosions! -wind driven, supported by hydrodynamic instabilities)

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18 Also: Blondin et al. (2010) (304x152x76 grid; 12M cpu-hours on Cray X1E at ORNL!)

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20 ... and GW signals from matter and neutrinos (Marek, Janka & Müller, 2009)

21 Summary (Part II) Core-collapse supernova explosions are triggered by neutrino interactions with matter and hydrodynamic instabilities Even the best models available predict weak explosions only What is the missing physics? Or are there numerical problems still?

22 Thermonuclear (Type Ia) Supernovae Examples: Kepler s supernova (1604) Tycho Brahe s supernova (1572)

23 Tycho Brahe 1601) ( : new bright star in Cassio- peia!

24 Stella Nova : Tycho Brahe s supernova

25 The standard model White dwarf star in a binary system Growing to the critical mass ( 1.4 M sun ) by mass transfer Disrupted by a thermonuclear explosion (fusion of C and O to iron-group elements) Light comes from radioactive decay : 56 Ni 56 Co 56 Fe

26 (Pakmor et al., 2008)

27 Thermonuclear supernovae: a problem of turbulent combustion Everydays experience: Turbulence increases the burning velocity. In a star: Reynoldsnumber ~ ! In the limit of strong turbulence: U ~ V B T! Physics of thermonuclear burning is very similar to premixed chemical flames.

28 The computational problem: Relevant length scales in simulations of SN Ia explosions beginning of the explosion: Kolmogorov scale Gibson scale flamelet regime ignition radius flame width resolution in 3D models WD radius resolved flame simulations (Woosley et al.) complementary small-scale studies(röpke et al., Schmidt et al.) SGS turbulence model Large-scale supernova simulations

29 Numerical realisation: Röpke et al. (2009)

30 Numerical realisation: Röpke et al. (2009)

31 Synthetic light curves... Kromer et al. (2010)

32 ... and spectra Kromer et al. (2010)

33 Supernova cosmology!

34 Mean distance between galaxies M = 0 open M < 1 M = 1 fainter closed M > 1 Redshift Billion years today time

35 Supernova calibration : (B-band light curves; Calan/Tololo sample, Kim et al. 1997) After calibration: SNe Ia look like good standard candles!

36 Models can explain the correlation! Kasen et al. (2009)

37 Summary (Part III) (Type Ia) Supernovae are well explained by thermonuclear-explosion explosion models of white- dwarf stars They are very good distance indicators in the local Universe and they allow to measure relative distances very accurately (after calibration) The calibration is justified (and even can be improved) by numerical models

38 Thank you for your attention!