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Supernovae of Type Ia

Supernovae of Type Ia

Ronald F. Webbink

Department of Astronomy

University of Illinois

SN 1994D in NGC 4526 (HST)

LSU - 25 Oct 07 2Hachinger et al. 2006

Supernova taxonomy

www.astronomy.com

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Cosmological significance

• SNe Ia as standard candles

• Magnitude => Expansion of light sphere with respect to comoving coordinates

• Redshift => Expansion of comoving coordinates

Wood-Vasey, et al. 2007

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All SNe Ia are

not the same

www.nd.edu/~kkrisciu

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• What is the physical cause of this dispersion?

• Is it truly independent of redshift?

• What secondary factors should affect SN Ia properties?

=> Physics of supernova explosions

• What are their progenitors?

www.nd.edu/~kkrisciu

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What do we know?

• Occur in both spiral and elliptical galaxies

Li 2007

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What do we know?


• Rate in spirals correlates with star formation rate (prompt component)

McMillan & Ciardullo 1996

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What do we know?


• Rate in spirals correlates with star formation rate (prompt component)

• Persistent rate among passive (elliptical) galaxies (delayed component)

Sullivan et al. 2006

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What do we know?

• Speed correlates with galaxy type

Gallagher et al. 2005

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What do we know?


• No H, He => MCSM < ~0.03 Msun

Lundqvist 2007

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What do we know?


• No H, He => MCSM < ~0.03 Msun

• Radio- and X-ray non-detections => dM/dt < ~10-7 Msun yr-1

Panagia, et al. 2006

Hughes et al. 2007

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What do we know about the progenitors?• White dwarf progenitors

No H, He

Some SNe Ia from old stellar populations

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No H, He

Some SNe Ia from old stellar

populations

• Thermonuclear runawaySpectra

No compact remnants found

Stehle, et al. 2005

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No H, He

Some SNe Ia from old stellar

populations



• Powered by 56Ni to 56Co

to 56Fe decaySpectra

Light curves Röpke et al. 2007

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No H, He

Some SNe Ia from old stellar populations



• Powered by 56Ni to 56Co to 56Fe decaySpectra

Light curves

• Binary systemsNo other plausible way to trigger instability

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Common envelope evolution

Yungelson 2007

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Stable mass transfer

Yungelson 2007

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SN Ia Progenitors

Yungelson 2007

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Candidate Progenitors• Single Degenerates

Cataclysmic VariablesRecurrent NovaeSymbiotic StarsSupersoft X-ray Sources

• Edge-Lit DetonationssdHe/HeWD + CO WD

• Double DegeneratesCO + CO White Dwarfs

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Cataclysmic Variables

• Outbursting binaries: Classical Novae (CN)

Dwarf novae (DN)

Novalike variables (NL)

Magnetic CVs (MCV)

• Mwd ~ 0.6-1.0 Msun

• Mdonor < ~2/3 – 1 Msun

• Accretion events (DN,

NL, MCV)

• dM/dt ~ 10-11 – 10-8 Msun yr-1

• Pcrit ~ 1019 dyne cm-2

=> Thermonuclear runaway

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Nova ignition masses

Townsley & Bildsten 2005

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Gehrz et al. 1998

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Classical nova outbursts

• Runaways erode Mwd!

• Many classical novae contain ONeMg white dwarfs

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Recurrent Novae

• Mwd close to MCh

• Ejecta lack the heavy-element enhancements characteristic of classical novae => dMwd/dt > 0 ?

• Core composition unknown, but likely to be ONeMg white dwarfs (cf. CN)

• Rare: Death rate ~ 10-2 SN Ia rate

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Symbiotic Stars

• Heterogenous class of objects, mostly wind-accreting WD companions to luminous M giants or AGB stars

• Hot components mostly powered by H burning on white dwarf

• Mwd mostly unknown, but those in T CrB, RS Oph (erstwhile RNe) must be near MCh

• Extremely H-rich environment

LSU - 25 Oct 07 26Munari & Zwitter 2002

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Supersoft X-ray Sources

• Heterogeneous class of objects (incl. PNNe, SNR, Symbiotic Stars), but many are stable H-burning white dwarfs

Nomoto et al. 2007

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• Population synthesis predicts ~103 SSS in M31 if SN Ia progenitors

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SSS in M31

center disk

Di Stefano 2007

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• Population synthesis predicts ~103 SSS in M31 if SN Ia progenitors => 102 times number seen in X-rays

• Can they be hidden?

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Evolution of SSS

Di Stefano & Nelson 1996

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Supersoft X-ray Sources• Can they be hidden?

• Perhaps super-Eddington luminosity (accretion + burning) drives a massive stellar wind

Hachisu & Kato 2003

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• BUT such a model predicts– H, He-rich ejecta

– Relatively dense stellar wind

both in violation of observational limits

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• Alternative: Super-Eddington accretion regenerates AGB giant

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• Alternative: Super-Eddington accretion regenerates AGB giant

• Maximum lifetime to carbon ignition (delay to SN Ia) ~ 1.6 X 109 yr

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Problems withSingle-Degenerate Progenitors

• Instability of He-burning shell

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Thermal pulses in AGB stars

Iben & Renzini 1983

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Thermal pulses in accreting white dwarfs

Cassisi, Iben & Tornambè 1998

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• Instability of He-burning shell– What of Surface Hydrogen Burning?

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Surface Hydrogen Burning

Starrfield 2007

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Surface Hydrogen Burning

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• Instability of He-burning shell• Ablation of H-rich donor in supernova event

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Marietta, Burrows & Fryxell 2000

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• Instability of He-burning shell• Ablation of H-rich donor in supernova event• Surviving companion?

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Companion peculiar velocities

Canal, Méndez & Ruiz-Lapuente 2001

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Tycho (SN1572) Companion?

Ruiz-Lapuente, et al. 2004

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Companion Rotation Velocities

Schmidt 2007

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Tycho G revisited

Schmidt 2007

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Edge-Lit Detonations• Degenerate ignition of ~0.1 Msun of He on ~1 Msun

CO white dwarf can trigger double detonation• Mass transfer too rapid from non-degenerate He

star donor to permit accreted envelope to cool to degeneracy and develop strong flashes

• Degenerate donors have even higher mass transfer rates until Mdonor < ~0.05 Msun

• Degenerate He ignition produces outward-propagating detonation, but fails to detonate CO core, or to produce intermediate-mass elements (e.g., Si) seen at maximum light

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Failed Double Detonation

Bildsten 2007

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CO +CO White Dwarf Mergers

• Wide range of delay times from GR inspiral

Yungelson 2007

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• Eddington-limited accretion ignites carbon at the base of the accreted envelope (1D)

Nomoto & Iben 1985

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• But mass transfer occurs on a dynamical time scale

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White dwarf coalescence

Yoon, Podsiadlowski & Rosswog 2007

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Merged Double White Dwarf

Yoon, Podsiadlowski & Rosswog 2007

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• But mass transfer occurs on a dynamical time scale

• Carbon ignition quenched in 2D or 3D by meridional expansion

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Problems withDouble-Degenerate Progenitors

• Tidal synchronization and preheating during approach to merger

Iben, Tutukov & Fedorova 1998

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• Angular momentum transport

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Synchronization at low accretion rates

• KH – Kelvin-Helmholtz instability

• BC – Baroclinic instability

• TS – Tayler-Spruit dynamo

Piro 2007

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• Angular momentum transport

• Shock heating of accreted matter and the site of carbon ignition

=> Neutrino cooling of accreted envelope?

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Are there enough double-degenerates?

Napiwotzki 2007

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Theoretical DD Search Yields

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SN Ia ProgenitorComparative Yields

Yungelson 2007

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The Parting Shot:We’re looking for haystacks, not needles!

Maoz 2007