Lessons from Spectral Evolution and

High-Velocity Features in

Core-Normal Type Ia

J. Craig WheelerOn Behalf of the Austin Mafia:

Howie Marion (+CfA), Jozsef Vinko (+ U. of Szeged), Jeff Silverman (+ UCB), Robert Quimby (+IPMU)

Texas A&M, April 9, 2103

Outline

I. Spectral Evolution – Deflagration to Detonation Models

II. => Single Degenerate?

III. High-Velocity Features (as opposed to High Velocity SN Ia)

IV. Collision with a CSM?

I. Conclusions

Typical Def/Det Composition Structure (Höflich et al. 2004)

My conviction: 1D deflagration to detonation models do a pretty good job of accounting for the multi-band light curves and spectral evolution of Core Normal SN Ia

Wheeler et al. (1998)

Blondin et al. (2013)

Optical, UV, NIR spectra

Pre-maximum to nebular

With some perturbation, off-center def/det transition, can account for polarization (Höflich et al. 2006)

Deflagration/Detonation models do a pretty good job of accounting for the spectral evolution.

Still uncertain physics of deflagration to detonation transition, but see recent work of Poludnenko et al. Paradigm shift through highly-resolved direct numerical simulations of turbulent combustion in hydrogen flames: no distributed flame.

1D Def/Det models are not the last word, but they set the bar: any competing model must do at least as good; not just light curves, but spectral evolution.

Röpke et al. (2012)

“Hard collision” of two white dwarfs, detonation.Issues with initiating, propagating detonation with level set methodLikely problems with polarization, nebular line profiles

Seitenzahl et al. (2103) – parametrized 3D Det/Def models, a challenge for the future.

Does the relative success of Def/Det models imply single degenerate progenitors?

Def/Det models seem to demand a relatively slow evolution to central carbon ignition in a carbon/oxygen white dwarf very near the Chandrasekhar mass, runaway to form deflagration, transition to detonation.

Consistent with classic models of single-degenerate evolution.

But

Relatively slow double-degenerate disruption (10s of orbits??) might do the job (Dan et al. 2011, 2012; but see Kasen talk).

High-Velocity Features

Seen prominently in Ca NIR triplet prior to maximum, but also in Ca H&K. Si II, other lines.

Clue to burning or to CSM?

Gerardy et al. (2004)

Quimby et al. (2006)

“Linear” blue wing in Si II

High velocity Ca II NIR triplet + OI? (Marion, Vinko, JCW)

Must observe well before maximum, early detection critical.

SN 2009ig beginning at -14 d (Marion et al. 2013)

Evolution of Si II (Marion et al. 2013)

High velocity and photospheric components of Si II, Si III, S II, Fe II (Marion et al. 2013).

Marion HET snapshot data

Evolution of High-Velocity Features and Photospheric Features (Marion et al. 2013).6000 km/s

Silverman – BSNIP data Ca NIR

HVF exist in all subtypes (core normal. 91bg, 91T), both high velocity and normal velocity in X. Wang classification scheme.

The high-velocity Si II blue wing extends up to the blue absorption of the Ca II NIR that extends to >30,000 km/s in blue wing (Quimby, et al. 2006)

High velocity Si II must come from the white dwarf

High velocity Ca from the CSM??

Chevalier – forward, reverse shocks, RT unstable contact discontinuity

H, He, primordial Ca

Contact Discontinuity

Si, IME

H, He, primordial Ca

Si, IME

Gerardy et al. (2004)

Gerardy et al. (2004)

Spectropolarimetry of Core Normal Type Ia SN2001el (Wang et al. 2001)

Ca II NIR High-Velocity feature is significantly polarized

HVF Conclusions

High-velocity features are common before maximum, but not universal (~90% ??; Silverman examining BSNIP data).

High-velocity features are distinctly separate from the photosphere by ~ 6000 km/s, kinematically detached.

High-velocity features are polarized.

Highest velocity HV Si ~ lowest velocity HV Ca.

Impact of SN ejecta on CSM shell, m ~ few hundredths of Msun, with primordial Ca gives a reasonable representation of the HVfeatures.

If CSM shell, must lie at << 1015 cm to avoid contamination of early light curve, must have large covering factor to be so common, but sufficiently asymmetric to account for polarization.

Conclusions

Deflagration to Detonation models work well for spectral evolution of Core Normal SN Ia (and some sub-varieties).

Consistent with, but does not demand single degenerate evolution

High-velocity features are strongly suggestive of a circumstellar structure of small mass (~ few 0.01 Msun) and radius (typical size of orbit, ~ 1012 cm, would probably be adequate).

Ca could be primordial, but do not know major constituent of CSM, H? He? C? O?

SD?? DD??

Credit: David A. Hardy

Type Ia