Different Kinds of “Novae”

Different Kinds of Different Kinds of “Novae”“Novae”

I. Super Novae I. Super Novae Type Ia: Type Ia: No hydrogenNo hydrogen, CO WD deflagration --> , CO WD deflagration -->

detonation detonation

SNe Ia progenitor unclear: SD and DD modelsSNe Ia progenitor unclear: SD and DD models Type II: Core collapse of (M >~ 8 M_sun) Type II: Core collapse of (M >~ 8 M_sun)

progenitorprogenitor

II.II. Classical & Recurrent NovaeClassical & Recurrent Novae

Thermonuclear runaway of accreted gas on WD surfaceThermonuclear runaway of accreted gas on WD surface Possible channel to SNe Ia???Possible channel to SNe Ia???

III. Dwarf Novae (Not Relevant Here)III. Dwarf Novae (Not Relevant Here) LLpeak peak ~ 10 L~ 10 Lsun sun (gravitational potential energy)(gravitational potential energy)

EEtot tot ~ 10~ 1040 40 ergsergs

SNe Ia: Observed Facts

General properties:• Homogeneous (small correlated variations)• Rise time: ~2-3 weeks• Decay time: ~ several months• Expansion velocities ~10,000 km/s• NO Hydrogen in spectra (almost always!)• Si, Ca, Mg (abs early); Fe (em late)• Seen in all galaxy types including ellipticals ([some]

progenitors must have long lifetimes)• SNe Ia in ellipticals generally less luminous

SN 2002ic: A SNe Ia with Hydrogen!

• Hamuy et al. (2003) Kotak et al. (2004)

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Proposed SNe Ia progenitors:Single Degenerate (SD)• Symbiotic Binaries (WD + RG)• Recurrent Novae (WD + MS)• SSS (> 10^-7 M_sun yr^-1?, but

see Starrfield et al. 2004)• Helium Star + WD binary• Hydrogen or Helium Accretion?

Double Degenerate (DD)• Binary WDs (>= Chandra mass)• Binary WDs (subChandra) Importance of Mass Ratio (e.g. van

Kerkwijk et al. 2010)?





Challenges of SD and DD Models

Single Degenerate:• ONeMg WD --> Accretion Induced Collapse (e- captures onto 24Mg)• Require CO WD (max mass ~1.1 M_sun from stellar evolution). How

to build up ~0.3 M_sun of material? i.e, How to avoid H flashes?• Are there enough binaries (constraints from active SSS population)?• H problem• Delay Time problems (Chris)

Double Degenerate:• Will merger lead to detonation?• May require q~1• Enough progenitors? (constraints from the SSS population)

From D. Townsley -- KITP 2009

Basic Nova PropertiesBasic Nova Properties

• Material builds up on the WD surface and slowly becomes degenerate (if dM/dt sufficiently low, i.e. ~< 10-7 M_sun per year).

• TNR on surface of WD leads to a nova eruption

• Luminous! MV ~ -6 to -10

• Peak luminosity & fade rate depend mainly on MWD, but also on TWD, dM/dt (and stellar population?)

• All novae are recurrent at intervals of ~101 - ~105 yr.

Classical Nova Ignition Masses

• Ignition masses depend not only on MWD, but also on TWD and hence dM/dt.

• For a given dM/dt, the higher MWD, the less material is accreted prior

to the TNR.

• The higher dM/dt, the hotter the WD, the hotter the WD (for a given WD mass) the less material is accreted prior to the TNR.

ownsley & Bildsten (2005)

Summary: Outstanding Nova & SN Ia Questions

1) In the single degenerate scenario, can the mass of a CO WD grow by the accretion of solar composition gas? (i.e., do H flashes blow off all accreted material?)

2) What are the likely candidate binary systems that are able to build up a ~1 M_sun CO WD (max mass from evolution?) to Chandra mass IF helium must be accreted?

3) If a 1 M_sun CO core accretes a layer of He at dM/dt ~ 10^-7 M_sun/yr, does the He burn steadily to C? (Starrfield et al 2004 say “yes” if the WD is hot enough) If not, can the (sub-Chandra) core detonate?, and if it does, what would the spectrum of the explosion look like?

4) What is the physics of binary WD coalescence: Can more (or less!) than a Chandra mass deflagrate, producing super (Sub) Chandra SNe Ia explosions? ... or ...

4a) Are WD mergers in super-Chandra binaries inefficient, resulting in generally lower Ni^56 yields and fainter SNe 1a? (ellipticals)

Different Kinds of “Novae”

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