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Supernova science in general

RHM
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This thread serves as the place to discuss supernovae in general, not just SN 2011fe.  Do you want to know why supernova explode?  What's the difference between a Type II and a Type Ia, or Ib, or Ic?  How can supernovae help us to understand the age of the universe?  This is the place to ask.

Predicted maximum magnitude
HOA
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People were making predictions shortly after discovery about how bright SN 2011fe would become. How is that predicted so early during the supernova's rise? Is it it done by fitting a light curve template over the existing data? I know that Type 1a supernovae are "standard candles." Does this mean their light curve fits a well-defined profile?

- Andy Howell

Yes, fitting a template yields a good estimate
RHM
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Type Ia supernovae are pretty good "standard candles".  They aren't all identical, but a decent fraction -- perhaps 30-40 percent -- are indeed very very similar in the shape and peak luminosity of their light curves.  Another 30-40 percent are significantly different: either narrower and dimmer, or broader and more luminous.  Over the past few decades, astronomers have discussed several ways that one can classify their properties and make small corrections to predict their degree of under- or over-luminosity, compared to the middle group.  One (simple) method uses the amount by which the object decreases in brightness in the first 15 days after maximum light to classify it; see the original paper by Mark Phillips in 1994 at

http://adsabs.harvard.edu/abs/1993ApJ...413L.105P


If you look at the graph shown near the top of my web page,

 

light curve of SN 2011fe and SN 1994D

 

you can see a comparison of the early light curve of SN 2011fe and the "normal" Type Ia SN 1994D.  I simply shifted the position of the SN 1994D data by hand until they matched up with the SN 2011fe measurements reasonably well.  The VRI curves seem to be following the pattern of SN 1994D, but we might be seeing a difference in the B-band; then again, that's just a single measurement, so it may not be meaningful.

Comparing the light curves of 2011fe and 1994d
HOA
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The V, R, and I curves track each other exceptionally well. I was a little surprised to see that. It will be interesting to see whether the future light curve of SN 2011fe continues to follow the pattern of SN 1994d.

In the case of the B light curve of SN 2011fe (Reference AAVSO LCG plot of SN 2011fe), I noticed it was below the V magnitudes soon after discovery. Then the B magnitudes "caught up" and seemed to equal the V magnitudes. In this respect, the behavior of SN 2011fe might differ from SN 1994d.

SN 2011fe is a bit bluer than SN 1994D
RHM
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Yes, you're absolutely right.  The graph below shows that while SN 2011fe is tracking SN 1994D pretty well in V, R and I passbands, it's a bit brighter in the B-band.  What exactly does that mean?  It's not clear yet.  I'd like to see a comparison of the spectra ... does anyone know where one can find recent spectra of SN 2011fe?

 

Light curves of SN 2011fe and SN 1994D as of Sep 12, 2011

AAVSO 49 Bay State Rd. Cambridge, MA 02138 aavso@aavso.org 617-354-0484