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Author Topic: The future use of type 1a supernovea as standard candles. Is it still feasable?  (Read 1128 times)

Offline Jonathan Raymond

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Okay, it's been a while (well, year or two) since I studied this, but if memory serves me correctly type 1a supernovae are used as standard candles as they're formed by white dwarves accreting matter and going supernova when they reach the Chandrasekhar limit (i.e. they all explode with the same mass, therefore they all have the same intrinsic brightness)
However this paper
newbielink:http://www.cfa.harvard.edu/news/2011/pr201123.html [nonactive]
suggests that rotating white dwarves can stay stable for longer, and go supernova when they're spin slows down enough to make them unstable.

So anyway, I was wondering, how much does this affect the ranger of masses that type 1a supernovae go off at? Does this significantly affect their use as standard candles?
Much thanks.


 

Offline imatfaal

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From my quick reading of the paper - that angular momentum must be conserved and that White Dwarves must be spinning is nothing new at at all, nor that this spin increased critical mass past that of the Chandrasekhar limit - the paper really concentrates on observational signatures of the progenitor, donor and remnants to dstinguish between the different formation methods of the WD. 

The change in mass (in terms of M_Ch the critical mass at which carbon fusion can start) - is minimum 5pct (ie 1.05M_Ch) and some models place it much higher (2M_Ch). The paper is also suggesting that simple WD that aren't spinning are hihgly unlikely - all we need for standard candles is that they are all much the same.   Reading between the lines I believe the authors think the lower bound is most likely.

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Of course, only a small fraction of donors can provide enough mass to allow the WD to significantly exceed MCh ; thus, the largest number of pre-explosion WDs should have masses very close to MCh
 

Offline PhysBang

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The fact that SNeIa might be exploding white dwarfs does not make them standard candles. They are not standard candles because, whatever they are, they have intrinsic variation in their brightness. However, this variation is highly correlated with the plot of their change in brightness over time so the variation can be estimated and individual events can be used effectively as standard candles.

So even if SNeIa turn out to be unrelated to white dwarfs, their use as something like a standard candle is pretty safe.
 

Offline imatfaal

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Thanks Fizz - I hadn't appreciated that fact about the variation.  On your first point - I thought type 1a were defined as exploding white dwarves, is there some doubt?
 

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