Isobel (preliminary ESI): z=0.582 (OII, Ca H&K from galaxy) SNIa features look good after subtracting some template.
Andy (preliminary ESI): I'm not so sure. It is very red. That is either due to galaxy contamination, reddening, or it is not a Ia. There certainly is at least galaxy contamination -- the SN is near the center of the host. I can't see anything that makes me say that it is definintely a Ia rather than a Ib/c. See the comparison beteween the 80 pixel smoothed, Sb galaxy template subtracted, ESI spectrum of Prokofiev and the Ic SN 1990aa (phase unknown) at z=0.582: Prokofiev.90aa.ps. Note that even though the spectrum of 90aa cuts off at 6000 A (4000 A rest), SNe Ic often do have the feature at 5500 A (3600 A rest).
Then again it could be a Ia. See the comparison to SN 1981b at max (a different amount of galaxy light has been subtracted, otherwise the spectrum was prepared as above): Prokofiev.81b.max.ps.
And it could even be a II if the redshift is wrong (this would require z=0.51).
Andy (Apr. 4, 2002) Lifan suggests this might be a Type Ia at z=0.85. However, I find that after running it through my program which does galaxy subtraction, the best match is SN 1989b.m01.dat, with an Elliptical galaxy subtracted at z=0.6. See Prokofiev.ps.