If the star is shrinking by 15% at a given wavelength, it is nothing
to worry about. 15% at all wavelengths is still nothing to worry
about, since Betelgeuse is a red supergiant. Like all red
supergiants, the distended outer layers are very thin and tenuous. I
don't have the figures at my hands, but if I remember correctly, the
chromasphere has a density of only a few hundred atoms per cubic
meter.

Thus, a contraction of 15% is interesting, but it may involve only a
solar mass or so of material. Nothing to get excited over.

PS: I found these links:
http://www.sciencenews.org/view/gene...lgeuse_shrinks
http://www.foxnews.com/story/0,2933,525695,00.html
Is either of these your links?