The two types of Ia supernovae

[Tom Mazanec]

I know that, in trillions of years, all Ia supernovae will be binary white dwarfs spiralling together, but what is the proportion viv-a-vis WD accreting off a "normal" companion 13.7 gigayears after the Big Bang? One scenario has a 1 solar mass WD going to a 2 solar mass WD and going BOOM, another has a 1.39999999 solar mass WD going to 1.40000001 solar masses and going BOOM. Can these be distinguished? How about seeing progenitors? Does the accreting WD give of X-rays, for example?
Any idea on which model is currently predominant?

[antoniseb]

... Any idea on which model is currently predominant?

Recent (last year or so) papers seem to indicate that the two white dwarfs spiraling into each other is much more common than a near critical white dwarf gaining the last bit of mass. The ratio of one verses the other could be anywhere from 3:1 to 100:1 depending on whose paper you read, but this should be regarded is new and still being confirmed.

[korjik]

Recent (last year or so) papers seem to indicate that the two white dwarfs spiraling into each other is much more common than a near critical white dwarf gaining the last bit of mass. The ratio of one verses the other could be anywhere from 3:1 to 100:1 depending on whose paper you read, but this should be regarded is new and still being confirmed.

You wouldnt think that they would be a standard candle if that were the case. Tho maybe the collison supernova is the same mechanism as an accretion supernova. Then you may have the combined mass be close enough to 1.4 solar mass often enough that they only look like standard.

[antoniseb]

You wouldnt think that they would be a standard candle if that were the case. Tho maybe the collison supernova is the same mechanism as an accretion supernova. Then you may have the combined mass be close enough to 1.4 solar mass often enough that they only look like standard.

I had a thread a while back on this topic. The fact that they are all so closely lined up showing red-shift to brightness is pretty amazing. I suspect that the process of creating two white dwarfs that can spiral into each other in less than the age-of-the-universe-so-far may guide the masses to typically be pretty similar (within say 10-20% (my wild guess)). Thus this is an important area of study right now. Being able to find SOME SNe that can be known to be standard candles to within a percent would be great. I don't know if we have that yet.

[ctcoker]

Well, really Ia SNe are not actually standard candles; they are instead standardizable candles. Their maximum brightnesses are related to the shape of their light curve (i.e., how their brightness fades over time), but there is in fact at least a factor of ~3 range in luminosity in observed Ia SNe as I recall (googling the Phillips relation would probably yield more info on this). If the light from Ia's is all generated the same way, the mass range of the exploding white dwarfs could easily explain this variation.