VLT Data files:

Date: 21 April 2001
Exposure time: 3 x 1200s = 3600s
Data reduced by: Chris
Weather note: Previously cirrus, now clear. Seeing 0.6 - 2.1" over course of night.
SN: [asc] [fits]
Sky: [asc] [fits]
Preliminary reductions: [smoothed ps] [unsmoothed fits]


Chris (preliminary): Possible HK break at z=0.48. Seems to be mostly galaxy. A faint SN?

Isobel (preliminary): I think its z=0.54. (gal OII and absn features) SN features match quite well. See: lalo_snz.ps.

Chris (final): SN Ia z=0.541 OII

Andy (final): Decent fit to 94D at +2 days, except that there is no Si at ~6000 observed (4000 rest). See S01-017.94d.p02.ps, where the data have been S-G smoothed, and 10% Sb galaxy has been subtracted.

Without Si, it is hard to say that this is a Ia. It is possible that this SN is on the hot side of normal SNe Ia, and there is weakish Si, like 90n, and what is left is buried in the noise.

It possible that this is a Ib/c. See the comparison to the Ib SN 1999dn at +10 days: S01-017.99dn.z56.ps These data have not been smoothed, nor has any galaxy light been subtracted. Note that this redshift is 0.02 off in redshift from what Chris reported. The data also fits at z=0.54, but not as well. While the data are not a perfect match, all of the lines are there. I also cannot stress enough the diversity of Ib/c. There is no earlier spectrum of 99dn, so it is hard to say what it would have looked like at peak.

You can also fit the same SN Ib (SN 1999dn at +10 days) at z=0.34: S01-017.99dn.p10.ps. The high redshift data is on top and has been S-G smoothed. In this case all of the features identified would be different than if the match was at z=0.56! This "match" is probably not correct, if Chris' determination of the redshift from the OII line is right, but it goes to show that we have to be very thorough when we are matching up spectra. Just matching wiggles can be very misleading, unless we have an unambiguous detection of Si of some kind.

And just to drive home this point even more, compare the spectrum to the peculiar SN Ia 91T at z=0.75: S01-017.91t.z75.ps As above, I don't think this is the correct "match," I am just making the point that without a redshift is is easy to match many things.

I would suggest downgrading this one to Type Ia? It is best fit as a Ia, but without the Si II it is hard to say for certain. It is possible that when we factor in light curve data it will seem more solidly like a Ia.

Light curves
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