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Originally Posted by Kwalish Kid
Yes, that is a supernova paper that mentions some theoretical astrophysics about the object of study. Yet nowhere does the paper endorse or rely upon that hypothesis.
I assume that you read the paper, so do you continue to make this claim that SNIa cosmology relies on this theoretical model?
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Did you even read my quote from the paper?
Originally Posted by Jerry
"Most of the time, this is a valid syllogism, but supernova research is exceptional.
The essential assumption in using supernova as standard candles is that the mass of each-and-every 'type Ia' event is very near the Chandrashakar critical mass of 1.6 solar."
Quote:
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Originally Posted by Riess et al
Theoretical models suggested that these “standard candles” arose from the thermonuclear explosion of a carbon-oxygen white dwarf that had grown to the Chandrasekhar mass...
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If you are arguing that 'the essential assumption' is not grammatically similar to 'Theoretical models suggested'; you are still missing the point. The spectra of the most distant supernova are very noisy - Read the Broder et al paper referenced by Antoinseb - it is an necessary assumption of every paper using supernova Ia for cosmological purposes that the distant sample has the same light-curve length/ magnitude relationship as the local sample.
1991T was the very first supernova type Ia that did not seem to follow the magnitude/light-curve width relationship established for type Ia supernova, diveraging from the exist lightcurve/magnituded relationship by four sigma - it was much too bright for its light-curve width. Certain spectral features were noted in the 1991T spectra, and these were used to segregate a group of local supernova type Ia from the spectral group used as standard candles.
Broder et al notes that 5 or of the high redshift have been observed that seem to contain this same spectral feature, and Broder notes that this feature presents a challange to the interpretation of distant supernova light curves: Is the distant sample observed more like the superluminous event 1991T, or are they more like garden variety Ia supernova?
As stated by Broder:
Quote:
...The identification of the 3 possible 1991T-like objects in this high-z sample nearly doubles the number of these sub-types observed at higher redshifts, but the percentage of identified 1991T-like SNe is still much lower than at low-z. It is difficult to determine the significance of this apparent discrepancy due to the unknown influence of selection effects.
For example, the low-z peculiar objects are often singled out for spectroscopic follow up and thus may be over-represented in the nearby sample. Another complication is the uncertainty with regards to whether the overluminous 1991T-like and 1999aa-like SNe are distinct sub-classes of Type Ia SNe or if they represent apossible continuum of thermonuclear SNe...
Another factor that may be contributing to this difference is the trend for the SNLS to find more slightly bluer, brighter objects (Astier et al. 2006). F04 noted that the evolution of different SNe along the mean trend for EW{MgII} correlated with luminosity, with brighter objects making the ‘jump’ to higher EW at later times. The small group of outliers below the EW{MgII} mean trend between +5 and +10 days may just be reflecting a slightly brighter group of SNe in the high-z sample. The average s value within these SNe is just above 1.0 [this corresponds to brighter SNe, see Fig. 9 in Astier et al. (2006)], which supports this hypothesis. This feature comparison may be more sensitive to slight differences in the strecth distribution of the samples than the other EW results. Further investigation into this parameter, both observationally and theoretically, is certainly warranted.
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