Surviving Companions of Type Ia Supernovae

Callum McCutcheon

Yunnan Observatories,

University of Surrey

Collaboration with Zhengwei Liu, Zhanwen Han, Xuefei Chen, Hai-Liang Chen, Kuo-Chuan Pan

Background

• Competing theories for Type Iageneration• Single-degenerate – WD +

MS/RG/He

• Double-degenerate – WD + WD (WD+NS/BH)

Background – SD channel

• SD will leave behind companion star (remnants!) – potential method to discern between the channels

• Properties of surviving star could help to determine properties of binary system before explosion• Kick velocity

• Heavy element distribution

• Simulate impact of ejecta on companion

Changing explosion model

Pan, Ricker, Taam, ApJ, 2014

• Hard to reconcile SD scenario with surviving companion candidates after long-term evolution (SN 1572, SN 1006, SNR 0519-69)

• If changing companion star model does not quite fit, try changing explosion model!

• Explosion models differ in abundance spatial distribution, velocity, etc.

Hydrodynamic codes - approaches

• Two main approaches – Grid/SPH

FLASH - Grid-basedHighly modular AMR grid-based code

Can be adapted for different solving regimes, grid structures, equation of state etc.

Advantages:• Should resolve structure of lower-density gas with

better precision• Shock treatment is effective – hopefully can

estimate shock heating temperature.Disadvantages:• Uniform grid wastes memory on vacuum -> use

Adaptive Mesh refinement• Can present grid artifacts

Using Helmholtz EOS – more complex than Γ/ideal-gas𝐹 = 𝑈 − 𝑇𝑆

9-species nuclear abundance network1H 3He 4He12C14N16O20Ne24Mg56Ni

Multipole gravity solver

Simulation

• Code written for FLASH 3 – 3D, metal tracing, particle simulation

• Current version for FLASH 4.6 – 2D cylindrical

• Aims:• Import new companion star models from MESA

• Edit code to allow for new supernova explosion models e.g. W7 with updated abundances, N100 so far.

• Adapt FLASH 3 code improvements to newer version – allows us to look at flows more accurately, capture of material.

• Export surviving companion model for long-term evolution – MESA

Resolution: 11 levels of refinement around star+SN9 elsewhere

~15-18,000 blocks of 8x8 grid cells.

Companion star model is late main-sequence, 1.16 M⊙.

Preliminary results – W7

Resolution:10 levels of refinement around star+SN8 elsewhere

12-14,000 blocks of 8x8 cells.

Companion star model is close to ZAMS.

Resolution

AMR: x/y

x is max. levels of refinement outside of star regiony is max. levels of refinement inside star region

Pan, Ricker & Taam (2010).

Resolution issues

Left: resolution 9/11Right: resolution 7/9

Instabilities on small scale might be exaggerated at short timescales – non-spherical shape. Appears to be solved by using shell-based supernova model.

N100 (1D angle-averaged) with 1.16 M⊙ late MS star. P= 1.18 days.

Left: main sequence ‘B’ (Pan et al. ApJ 2012)Right: late main sequence, sub-solar mass ‘model 3’

N100 companion comparison

Main parameters to retrieve:

Elemental distribution – want to perform long-term evolution simulation of the companion (e.g. 56Ni)

Shock heating – want to estimate luminosity of SN to match with observations

Ejecta cavity angle – important implications in SNR shape.

Future plans

• Simulate WD during companion star relaxation – inspect effects of Roche-lobe shape.

• Move to a 3D simulation – more accurate depiction of ejecta asymmetry, instabilities (mixing?)

• Include rotation and orbital motion – better estimates for companion kick velocity

• Radiative transfer calculations in FLASH – RadTrans module available in version 4.

Thank you for listening!