|
An extract from Steve's recent emails:
Leaving the data in wavelength masks important information. Put
instead, in velocity, you convert the profile into a map of the ejecta.
In the sense that the radial velocity depends on radius, for fixed
orientation relative to the observer, the higher velocity parts of the
profile are from the outer portions of the ejecta (this would be true
for a wind too, as in a classical P Cyg profile).
By doing this you also can compare profiles of different ions,
for instance seeing how the Balmer lines change (which is the same ion,
neutral hydrogen) or the changes in the resonance line of Na (the D
lines) compared with [O I]6300, say, which is a forbidden line and
traces lower density gas.
Once you've done this simple step you start to see a lot of the physics,
and the time dependence starts to make sense because you can
compare across excitations and ionizations.
Try comparing Halpha and Hbeta, that's the simplest to get a feel for
the optical depth variations in the absorption component. There's also
a progression -- the H-beta absorption is at a lower velocity than
H-alpha because it's formed (from our point of view toward the ejecta)
further inside (in other words, you have to look geometrically deeper
to get the same optical depth). Then Na I 5889.95,5895.92, when it's
observable He I 5876, the multiplet Fe II 4923, 5018, 5169, and the O I
6300, 6364 doublet. When it's observable, N II 5755. These should be
a good start.
|