Supernova light curves - photometric analysis

Hi everyone - I'm looking for web references that explain the physics
behind the different shapes of SN light curves obtained when performing
photometric analysis at different wavelength (U,V,B,R,I). Appreciate
your assistance with this.

Alex

I don't know enough about the physics to separate the
grain from the chaff, but Google's new Scholar search
is your friend:

http://scholar.google.com/scholar?q=...analysis+bands

HTH

xanthian.

Alex wrote:

Hi everyone - I'm looking for web references that explain the physics
behind the different shapes of SN light curves obtained when
performing
photometric analysis at different wavelength (U,V,B,R,I). Appreciate
your assistance with this.

I suspect strongly that there is no good, simple
explanation of the physics underlying the difference in light
curve shapes at the level you are seeking. For one thing,
one must discuss the radiative transfer of energy through
an expanding shell of gas with varying temperature, density and
chemical composition. It's a very difficult problem
if you want to get into the details.

At the simplest level, treat a supernova explosion as
an expanding blackbody. As the supernova ejecta expands,
its surface area increases (that makes it more luminous),
but its temperature decreases (that makes it less luminous).
At very early times, the expanding factor wins, and the
supernova grows brighter. At late times, the cooling factor
wins, and the supernova grows fainter. In this very simple
approximation, one might expect almost identical light curves
in each passband ... but not quite. The blue passbands
would evolve more quickly because they sample light on
the exponential tail of the blackbody spectrum, which is
more sensitive to temperature.

At the next level of approximation, you can try
to figure out where the "photosphere" of the star
lies within the expanding ejecta. In Type II SNe
explosions, which have massive, H-rich envelopes,
there is a pseudo-photosphere within the gas
at the point where hydrogen is just recombining
(i.e. changing from ionized to neutral); this occurs
at a temperature of several thousand degrees. As the
ejecta flies outwards, the pseudo-photosphere is
carried with it ... but it also gradually moves
inwards (in a relative sense) as the ejecta thins and cools.
If you treat most of the visible light as emitted
in this pseudo-photosphere, you can do a better
job of re-creating the light curves in
different passbands. You might read papers
on the "Expanding Photosphere Method" to learn
more about this subject.

Beyond that, it gets really complicated :-(

Michael Richmond