The Many Guises of Thermonuclear
Supernovae
Wolfgang Hillebrandt

Supernova Conference
YIPQS, Kyoto
October 31, 2013

Work in collaboration with:
Stefan Taubenberger, Ashley Ruiter, Markus
Kromer, Assaf Sternberg, Sandra Benitez, Uli
Noebauer, Philipp Edelmann, Michele Sasdelli(MPA)
Elisabeth Gall (MPA/QUB/ESO)Friedrich Röpke, Ivo Seitenzahl, Michael Fink,
Stephan Hachinger (MPA/Würzburg)
Stuart Sim (MPA/ANU/QUB),
Rüdiger Pakmor (MPA/HITS)
Paolo Mazzali (MPA/INAF Padua/Liverpool)
Zhengwei Liu (MPA/Kunming Obs.)Thermonuclear (Type Ia) supernovae: They are a homogenous ‘class’ They make most of the iron in theUniverse They make some p-process elements
 Some of them make n-rich isotopes suchas 48 Ca, 50Ti and 54Cr They can be used as distance indicators………….
This is based on the assumption that they are
all Chandrasekhar-mass C+O white dwarfs

The standard ‘single-degenerate’ model Growing to the criticalmass (Mchan ≈ 1.4 M  )by mass transfer
 Disrupted by a thermonuclear explosion (fusionof C and O to iron-groupelements)
 Light comes fromradioactive decay :56Ni → 56Co → 56Fe
 White dwarf star in abinary system with MS or(R)G star

Thermonuclear (Type Ia) supernovae:
Can we be sure about all of this?

Can we be sure about this?
Example: SN 1572 (Tycho’s supernova)

Can we “see” this supernova still today?
Yes, by its light echoes!

© D. Maoz

X-ray spectrum (Badenes et al. 2006): M(Fe) ≈ 0.74Msun

Thermonuclear (Type Ia) supernovae:
How ‘homogenous’ are they as a ‘class’?

The ‘Branch normals’ and other SNe Ia:

Branch et al. (1993), based on a sample of 84 SNePeak luminosty/light-curve shape correlation:

Phillips et al. 1999

A recent Phillips relation:
the “beauties” and the “beasts”© S. Taubenberger

An example of a ‘weird’ SN Ia:
SN 2009dc
“very bright”
“unusual color”
“slow”
 “C-rich”

The properties of 09dc (and other verybright SNe Ia)
 High peak luminosity, broad light curves & lowejecta velocity large Ni mass (?) (~ 1.2 Msun of 56Ni)
 large ejecta mass (?) (> 1.4 Msun)
At the same time unburned material at rather lowvelocities

What are they ????

Other ‘weirdos’: ‘91bg like’:

low luminosity (~0.1 Msun 56Ni), evidence for unburned
C & O; strong Ti absorption ‘02cx/05hk like’:
sub-luminous (~0.2 Msun 56Ni), narrow lines ‘05E/05cz like’:very low Ni masses (0.01 – 0.05 Msun), Ca rich, He lines,
low ejecta mass(?)

What are they ????

‘Weirdos’ are not rare! Relative rates:(Li et al., 2011)‘‘

The ‘zoo’ of (possible) thermonuclear
explosions ‘Single degenerates’● Chandrasekhar mass
Pure deflagration‘delayed’ detonation● sub-Chandrasekhar mass ‘Double degenerates’● C/O + C/O● C/O + He

Which of them are realized in Nature? All of them?

A few examples:
1. ‘Pure deflagration’ SD (MNi ≈ 0.2Msun)

Synthetic lightcurves:

Typical ‘pure
deflagation’ model(blue)
compared withvarious ‘normal’
SNe Ia (red) andSN 2005hk(green)

Synthetic spectra:‘Puredeflagation’models (red)fit somepeculiar faintSNe Ia(SN 2005hk,blue), but neither‘normal’ norsubluminousones

Are the SN 2005hk-likes the ‘puredeflagration’ Chandrasekhar-massexplosions???

2. ‘Delayed detonation’ SD (MNi ≈ 0.6Msun)

DDT model, angle averaged (black solid lines)‘Delayed detonation’ Chandrasekharmass explosions fit lightcurves (andspectra ) of ‘normal ’ SN Ia well.
Do we need anything more???

Canonical Mchan DD models do not follow thePhillips relation and they are too ‘red’ !

Sim et al. (2013)

Are some SNe Ia (or all?) ‘super-Chandra’mergers and/or ‘sub-Chandra’ detonations???

The basic idea:
Let there be detonatins only!

The different luminosities of a SN Ia (the mass ofradioactive 56Ni) may be a result of different
white dwarf masses !

An example: ‘subChandra doubledetonation’ model

Fink et al. (2010)

Synthetic LCs ….

Kromer et al. (2010)

…. and spectra

Blue lines: SN 2004eo 3d before Bmax (Kromer et al. 2010)

A second example: ‘double-degenerate’ merger

Pakmor et al. (2011)

Violent merger of two WDs of ~ equal mass: Detonation likely

 Will be faint (in general, if M ≈ 0.9 M  )Synthetic LCs ….

Pakmor et al. (2010)

…. and spectra

Pakmor et al. (2010)(density color coded)

Pakmor et al.
(2012)

Dynamical merger of two WDs of similar masses:
 Detonation still likely

 Could be bright if more massive one has M ≥ 1.0 M Dynamical merger of two WDs of similar masses:
1.1 + 0.9 M , light curve predictions

Can we get more information on theprogenitors?
1. Direct observations: SN 2011fe in M101 (d~6 Mpc)

Li et al. (1011): donor was not a red supergiant!

2. Supenova remnants in the LMC

© D. Maoz

No star down to 0.5 Msun ! (Schaefer & Panotta 2012)

3. What else can we do to get information onthe progenitors?

Circum-stellar gas
Stripped gas from a (MS) companion:(Liu et al. 2012)

Was never seen!

Circum-stellar gas
Variable Na ID absorption (e.g. SN 2006X,Patat et al. 2007 )Evidence forcircum-stellar gas!
Only seen in SNein spriral galaxies!
Recurrent nova?
Or also in someDDs?

Rates and delay times
Expected delay times:~ t-1(DDs)~ t-0.5+ cut-off(SDs)(Ruiter et al. 2011)

Peak-luminosity distribution from DD mergers:
Observed distribution: grey shaded (Li et al. 2011)
Normalization to green distribution (η = 0.75)(Ruiter et al. 2012)

Summary and conclusions
SNe Ia: where do we stand?
 Type Ia Supernovae are well explained bythermonuclear explosion models of white dwarfs,
but they form a rather inhomogenous class!
The normal ones (~70%): What are they? MostlyDDs?
The ‘abnormal’ ones make up for 30% (or more).
Why are they ‘different’? Different progenitors?
How can we separate them from the ‘normal’ ones’
if we have broad-band photometry and one (or atmost) two colors only (as in future cosmologysurveys)? Evolution???

 If all (or most) of this is correct there should bemany ‘fast and faint’ transients which have escaped
discovery (low-mass mergers, low-mass coredetonations, low-mass edge-lit detonations ...).
Where are they? Or have we seen them already?

SN2005ek?

Kasliwal et al. 2010

red curve:edge-lit
detonation,
0.57 Msun C+O
0.21 Msun He
black dots:SN 1885A(S Andromeda,de Vaucouleurs& Corwin 1985)
Sim et al., in
preparation