Quote:
Originally Posted by Merlin66
Thanks for sharing!
Clouded out again down here in Melbourne!
The nova appears to be brightening again and the Ha emission seems to still be on the increase.....
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Clouded out here, too.
The re brightening seems to have peaked on Thursday night and a slow fade started, but it's hard to tell from the AAVSO light curve as there's so little photometry being done. From our spectra we see Ha increasing.
But at the same time the B-V value is
decreasing -i.e. the star is getting bluer. This seemed odd at first. But I'm guessing that when a significant part of the star's flux is Hydrogen emission, the usual BV shorthand for star colour doesn't work so simply. It's fine for normal stars that basically follow black body radiation curves; if B is brighter than V then V will also be brighter than R; there's a slope across the spectrum determined by the star's temperature. But here, with both Ha and Hb contributing more and more, B-V will decrease, but V-R will increase; that is, the star will be getting both bluer and redder. Rather than a Planck black body curve there will be a saddle-shaped curve with a dip centred around about 5600 A, right in the middle of the V band.
I wish I had an R filter! Not to mention IR for the dust phase to come. Santa, are you listening?