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Now we have the time of maximum light we can see if this supernova really is unusual or not. Here is the actual position of my spectrum taken on 2019-05-12 on the SNID time, redshift plot, marked in blue (I have assumed the redshift is that of the host galaxy)
We can see that this is not typical of most type Ia (because the expansion velocity is higher than usual), but there are a few other similar supernovae. If we look at these in SNID we find they are sn2004dt, 1984A, 2002bo. Looking in the literature I found this reference.
https://ui.adsabs.harvard.edu/abs/2007A ... A/abstract
There is a plot of velocity of the Si II line in fig 6. I have plotted my result for 2019ein.
We can see that it is similar to sn2004dt,1984A and 2002bo, with a higher velocity than the other more typical Ia supernovae. We should be able to follow this supernova for a while longer so If you want to measure your velocities in the Si II line in your spectra, I can plot them on the same graph.

Cheers
Robin

Cheers
Robin

I have added the Si II velocity from my spectrum last night and the velocity at -10 days from ZTF/SPRAT in TNS. It seems to best match the curve for sn2002bo with a very high initial velocity and a steep decline, though it is still higher than a typical type Ia

Robin

Hello

Here is the last spectrum I observed on the night of May 21st :


A comparison with my May 12 spectrum


This spectrum seems to match what you say Robin
I also note a line in emission at 4916A

Pascal

Hello Pascal,

Pascal Le Du wrote: I also note a line in emission at 4916A

Pascal

Yes I am seeing the same new feature
Cheers
Robin

Spectrum taken with a 1 meter telescope at Calern observatory with Pascal Le Dû, Bertrand Guégan, Pierre Dubreuil and Olivier Garde

6 x 600s exposures with a LISA and a 50 µm slit.

Hello Olivier and all,

Very nice spectrum Olivier! What resolution and RMS error did ISIS report when you processed this spectrum? This should be interesting to compare to the spectrum I took last night with my LISA using the 23 micron slit on my 00000.355 meter telescope at the famous Desert Celestial Observatory in Phoenix Arizona:) This was 9 600s exposures. I could not find any hot pixels or cosmic rays in the spectrum nor sky background to explain the emission peak at around 4602Å. I think I see maybe the same feature in your spectrum.

Woody

Hi Woody,

ISIS report a resolution about 540 and RMS calibration around 0,2 (I use an ATIK 414ex in bin 1x1 and a 50 µm slit because I have more than 5 meters focal length....)

Superbes spectres !
Olivier ton spectre de SN à un sacré signal ! Par contre on dirait un spectre haute résolution, les raies d'absorption sont très étroites, ça vient de quoi ?

etienne bertrand wrote:Superbes spectres !
Olivier ton spectre de SN à un sacré signal ! Par contre on dirait un spectre haute résolution, les raies d'absorption sont très étroites, ça vient de quoi ?

Il n'y a rien de particulier dans le process de ces spectres, la seule différence vient de l'optique. Après j'ai passé pas mal de temps pour optimiser au mieux la mise au point du doublet interne du LISA et au bout du compte la résolution du LISA avec la fente de 50µm est d'environ 540.

A spectrum from last night and the evolution over the past week.
It looks like the velocity in the Si II 6355 line has stopped falling. Similar to SN1984A for example
Robin