An Atypical Type 1a SN

[antoniseb]

Supernova paper:

http://arxiv.org/pdf/1207.1306.pdf Another good-news bad-news - they have possibly identified the source object(s); the bad new is there are a lot of atypical spectral lines in the explosion spectra; meaning this may be a not-so-normal type Ia event.

I pulled the above from Jerry's post in Fun Papers today.

The general trend in papers on type-1a progenitors lately has been toward showing that double-degenerate (i.e. two white dwarfs spiraling in to each other) is the most common way that type 1a SN happen. This paper shows an example of something that may be more of the classic model (a white dwarf going over the Chandrasekhar Limit from material pouring onto it from a companion). It may be that there is something unusual going on here, and it isn't a straight-up symbiotic type 1a, but the spectra are unusual, and more examples of this kind of 1a might provide better tools for sorting out which are the most standard of our type-1a standard candles.

[TooMany]

Can these spectral details currently be observed in the distant SN needed to establish the cosmic acceleration rate, so that the true expected luminosity can be derived (eventually).

[antoniseb]

Can these spectral details currently be observed in the distant SN needed to establish the cosmic acceleration rate, so that the true expected luminosity can be derived (eventually).

This one was observed at 700 million light years (5% of the way to the edge of the visible universe). In five-ten years, the 30 & 40 meter telescopes will be working, and we should be able to get this quality of data out another factor of 3 to 10 (assuming improvement in the detectors as well as surface area)... so yes. However part of the point here is that these are rare, and may not be the standard candle anyway. More study needs to be done on how to sort these things out. In the mean time, the double-degenerate type 1a SNs are generally the same brightness within a narrow range, so they don't give precision for individual events, but taken in statistical quantity, they still tell us a lot.

[Jerry]

It is going to be hard for any other family of observations to overtake, or even collaborate, Type Ia events as the golden cosmological standard candle. I wish - hope - that as the sample of well studied events swells, the reliance upon the statistical norm will be more pronounced than the 'knob turning' that dominates the current obsession with precision.

One fly in the ointment is any distance evolution that may be occurring - there are papers both ways on this; but with the high levels of metallicity found in most distant, well-developed galaxies, it should be reasonably safe to assume that if the same spectral patterns emerge, the sample is not evolving, either.