Models of Type Ia supernova explosions

Transcription

1 Fifty-one erg workshop Raleigh, May 14, 2013 Models of Type Ia supernova explosions Julius-Maximilians-Universität Würzburg, Germany I. Seitenzahl, M. Fink, R. Pakmor, S. Sim, M. Kromer, A. Summa, F. CiaraldiSchoolmann, A. Ruiter, Z. Liu, S. Ohlmann, K. Marquardt, W. Hillebrandt & The Nearby Supernova Factory

2 The progenitor problem What is it, that explodes? no direct observation compact star WD (Nugent+ 2011; Bloom+, 2012) no H, He C+O WD Inert object Why does it explode? (Illustrations: NASA/CXC/M.Weiss)

3 Connecting explosion models to observations Modeling pipeline:

4 Goals construct model sequences What part of the observed sample can be covered? How well does a model fit the observations? Does a model sequence reproduce trends and correlations between observables? Understand characteristic properties of models: What imprints do progenitor structure and explosion physics leave on observables?

5 The Chandrasekhar-mass story (Illustration: NASA/CXC/M.Weiss) textbook wisdom on SNe Ia why? provides good reason why thermonuclear burning commences seems to explain homogeneity 1D parameterized models fit observations well (e.g. W7 model of Nomoto+, 1984) potential progenitor systems do exist (U Sco, RS Oph...)

6 Flame propagation and burning hydrodynamics of flame propagation deflagration subsonic detonation supersonic flame mediated by thermal conduction of degenerate e flame driven by shock waves

7 MCh model: turbulent combustion subsonic bring WD material ahead of flame out of equilibrium pre-expansion Re~1014 fuel ρ > buoyancy instabilities lead to flame front turbulent combustion ash ρ <

8 MCh model: turbulent deflagrations t = sec

9 MCh model: turbulent deflagrations t = sec

10 MCh model: turbulent deflagrations t = sec

11 MCh model: turbulent deflagrations t = sec

12 MCh model: turbulent deflagrations t = sec

13 MCh model: turbulent deflagrations t = sec

14 Suite of 3D MCh models Seitenzahl+ (2012), Fink+ in prep. MCh WD

15 Failed deflagrations Fink et al. in prep

16 Suite of 3D MCh models Seitenzahl+ (2012), Fink+ in prep. MCh WD model N5 (5 ignition kernels)

17 Failed deflagration good match to SN2002cx-like supernovae (Kromer+, 2012)

18 SN Ia sub-classes and fractions volume-limited (Li+, 2010) 02cx 3% 91T 9% 91bg 18% Normal 70%

19 Suite of 3D MCh models Seitenzahl+ (2012) model N100 (100 ignition kernels) MCh WD

20 Delayed detonation model N100 t = 0.70 s

21 Delayed detonation model N100 t = 0.93 s

22 Delayed detonation model N100 t = 1.00 s

23 Spectra of delayed detonation model sequence Sim+, subm. comparison with observations using the SNID tool (Blondin & Tonry, 2007) following Blondin+, 2011 generally good agreement as quantified by the goodness-of-fit parameter rlap, typically > 7 best matches for intermediate deflagration strengths

24 Lightcurves of delayed detonation model sequence Sim+, subm.

25 Width-luminosity relation Sim+, subm.

26 Violent mergers of white dwarfs Are there enough systems that can grow WD to M Ch? Probably not. alternatives: detonation in sub-m WD triggered by detonation in He shell ( double detonations, Ch e.g. Fink+ 2007/2010, Kromer ) or instabilities in the accretion process mergers of white dwarfs (e.g. Pakmor+ 2010/2011/2012) (Illustration: NASA/CXC/M.Weiss)

27 Violent WD-WD mergers M1 =1.1M M2 = 0.9M (Pakmor+, 2012) inspiral and merger: 3D SPH code (GADGET3)

28 Violent WD-WD mergers explosion: 3D MPA SN Ia code (LEAFS) of n itio n ig o ati n to de n

29 Violent WD-WD mergers radiation transfer: 3D monte carlo (ARTIS) light curves spectrum good agreement with observed normal SNe Ia

30 How robust is the scenario? Pakmor+, ApJL accepted simulation with moving mesh code AREPO (Springel 2010): accretion stream sets off detonation in surface helium layer (0.01M ) drives shock wave into C+O core secondary detonation accretion from C+O or He companion wide variety of mass ratios possible explanation for bulk of normal and fast declining SNe Ia?

31 Synthetic optical spectra delayed detonation model SN 2011fe merger model SN 2011fe Röpke+, 2012

32 Breaking the degeneracy: gamma-ray observables? sensitivity of current gamma-ray observatories is insufficient (even for nearby SN 2011fe...) Summa+, 2013

33 Breaking the degeneracy: late photometry? Röpke+, 2012

34 Summary pure failed deflagrations of MCh WDs match observables of 2002cx-like SNe Ia reasonably well delayed detonations of MCh WDs can cover brightness range of normal SNe Ia, provide good overall match with observed properties of SNe Is, but have some shortcomings in several details How severe are these shortcomings? violent mergers of WDs provide a good alternative Explanation for bulk of SNe Ia? (model sequence underway) other scenarios may contribute as well for peculiar subclasses hard to distinguish from near-maximum light optical observables elemental (or even better: isotopic) abundances could help to constrain explosion models