Type Ia supernovae result from a white dwarf reaching the Chandrasekhar mass limit of 1.44 solar masses through accretion from a binary companion. The document discusses the history of understanding the progenitor system of Type Ia supernovae, including early theories of single degenerate systems and double degenerate mergers, as well as observations ruling out some candidates like super soft X-ray sources and favoring others like recurrent novae. However, the exact progenitor remains uncertain, with the current leading theories involving either a single degenerate or double degenerate system.

1. Type Ia Supernovae
A chronological attempt at
determining their progenitor
http://universeadventure.org/fundamentals/images/light-tycho.png

2. Layout
• Introduction:
– What are type Ia supernovae (SNe Ia)?
– Why are they important?
– What is needed?
• Necessary Components:
– Chandrasekhar’s mass limit
– Classical novae
– Recurrent novae
– Super soft X-ray sources
– Single and double degenerate scenarios
– Binary systems
• Trip Through Time (1980’s to current day):
– Lets find out what we know
• Summary:

3. Introduction
What are type Ia supernovae (SNe Ia)?
• They originate from white dwarfs (WDs)
• A super explosion releasing around 1-2 x1044 Joules
• Occurs when the WD reaches the Chandrasekhar mass limit ~1.44 M⊙
• No hydrogen seen in their light spectra
Why are they important?
• Used as standard candles for distance measurements
• Responsible for most of the iron abundance in the
universe
What is needed?
• A long period of stable accretion onto the WD, so it can grow
https://www.llnl.gov/str/SepOct08/hoffman.html

4. Necessary Components (1)
Chandrasekhar’s mass limit ~1.44 M⊙:
• Is the maximum mass a white dwarf can have before collapsing
• SNe Ia explodes due to a runaway carbon reaction in the core
Classical and recurrent novae:
• These are caused by thermonuclear runaway reactions on the surface after excessive
hydrogen compression
• Classical novae have been ruled out, due to more mass been removed than accreted
• Recurrent novae lose less mass than it had accreted
Super soft X-ray sources:
• These are very hot (>50 T ⊙) and luminous (>5000 L ⊙) WDs
• Hydrogen burns into helium on the surface immediately leading to no novae
explosions.
http://arxiv.org/pdf/0911.5254v3.pdf
Novae evolution

5. Necessary Components (2)
Single degenerate scenario (SDS):
• The WD accretes matter from a sub-giant,
main sequence, red giant star or AGB star
Double degenerate scenario (DDS):
• The WD accretes matter from another
WD before colliding
Cataclysmic Variable (CV) [Any star]:
1. Roche lobe is filled, accretion occurs through
the Lagrangian point
Symbiotic Variable (SB) [RG or AGB only]:
1. Roche lobe isn’t filled, accretion occurs only via
strong winds
http://www.daviddarling.info/images/contact_binary.jpg
http://astronomy.swin.edu.au/cms/cpg15x/albums/userpics/typeiaprogenitor1.jpg

6. Trip Through Time (1980’s)

7. Trip Through Time (1990’s)

8. Trip Through Time (2000-2009)

9. Trip Through Time
(2010 to current day)

10. Summary
In a sentence:
We still have no idea what the progenitor is!
• SSS WDs were favoured up until the beginning of
the century but have now been ruled out
• Recurrent novae are strong contenders, though confusion over
observations of T-Pyx might be an issue
• The double degenerate scenario started off weak pre 2005 but since
then they have become strong contenders due to the effects of
rotation
• Final word:
If we say the progenitor is a combination of both the SDS and
DDS, it would lead to SNe Ia being poor “Standard Candles”!