SN Taxonomy

                      Michael Richmond
                        May 12, 1996

  Well, the "splitters" have been beating the "lumpers" in the SN
classification business lately, so there is some new terminology.
Let me exercise my memory here...

   SN Type      characteristics                      guess at progenitor
 -------------------------------------------------------------------------
     Ia         no hydrogen in spectrum              white dwarf that accretes
                strong absoption at 6550 A               > Chandrasekhar mass
                      near max light                 two white dwarfs that
                late-time spectrum iron-group            collide
                      emission lines

     Ib         no hydrogen in spectrum              massive star which has 
                absorption near 5700 A, due to           been stripped of H
                      He (plus other He lines)           before core-collapse?
                late-time spectrum emission from     Wolf-Rayet star?
                      OI, CaII

     Ic         no hydrogen in spectrum              massive star which has 
                no helium in spectrum                    been stipped of H and
                late-time spectrum emission from         He before core-collapse
                      OI, CaII                       Wolf-Rayet star?

     II-P       hydrogen in spectrum,                massive red supergiant
                      with P-Cyngi profile
                light curve has plateau for 30-90
                      days soon after max light

     II-L       hydrogen in spectrum, weak or        less massive supergiant?
                      no P-Cygni profile             lost some of envelope?
                light curve falls linearly after
                      max light

     IIb        hydrogen in spectrum, but not much   massive star which has
                helium in spectrum                       lost MOST (but not
                late-time spectrum emission from         all) of its H 
                      OI, CaII, plus H                   envelope (in binary?)

     IIn        hydrogen in spectrum, with narrow    massive star which sits
                      emission lines on top of           in middle of massive
                      broad emission features            stellar outflow?
                slow decline in light curve at 
                      late times
                strong radio emitter?  some aren't

  There's also a paper in a recent A&A which suggests a new classification
scheme (based primarily on light curve properties?), but it hasn't been
widely adopted, as far as I know.

  The old Zwicky classes (types III, IV, V) are not used at all at the
current time, as far I as know.