spectro-aras.com

Congratulations on the spectrum Etienne. I think your result compares well with the professionals.

Paolo Berardi wrote: I don't know if SNID, the other tool for SN classification, provides the same performances.

The Chinese BAO team did not give any information on how they made the classification unfortunately.
EDIT: Another team using LOT used GELATO to predict type II
http://www.astronomerstelegram.org/?read=10374

Usually I find SNID works better than GELATO but I tried the BAO spectrum with SNID and it favoured type 1a-91bg spectra at 9-17 days after maximum with good confidence. The fits do not look very good to me though and we know the supernova is younger than that
Here is the best fit according to SNID The best type IIP fits look better to me though and the dates (6 and 7 days before maximum) are more sensible I expect we will know who is right in a week or two

Cheers
Robin

Hello Robin,

Thanks for your comments,
with my spectra, i find type IIP with 3.9 days :

Hi Robin, thanks a lot for the info about SNID. Did you have to provide the reddening value or the tool automatically adjusts the continuum? If I have understood that correctly, SNID works offline, without a web connection. I'd like to install but I'm not know the Linux environment, I wonder if I could use it on Windows OS using a virtual machine.

The SNID best fit seems also to me related with the two type IIP SN (the profiles are almost identical). Maybe human judgement it is necessary sometime to discard possibile unlikely solutions. Also the SN age is an important constraint.

Excellent achievement Etienne! Concerning your question about finding the minimum of P-Cygni absorption wavelength I think it's a bit risky relying on a particular peak when the random intensity fluctuations are of the same order of magnitude. Anyway, observing the continuum trend in that area, I think it shouldn't be too far from the point you found.

Maybe you already know, here you find a "classical" table that shows the main Sn types:

http://supernova.lbl.gov/~dnkasen/tutor ... _types.jpg

On the bottom the type II with the P-Cygni hydrogen alpha line composed of a broad emission and a narrower blue-shifted absorption. It is just a guideline, each case is in fact different. At present, the emission component of SN2017eaw is the large "bump" well visibile in your spectrum while the blue-shift absorption is difficult for me to identify even on the BAO profile. In the next days/weeks we'll see if the feature becomes appreciable. Expansion velocities measured with P-Cygni tend to decrease over time, so the absorption will be closer to the emission component, either way, it could become more pronounced.

Paolo

Very good your schema, it makes it possible to better understand the phenomenon

Hi Paolo

Paolo Berardi wrote: Did you have to provide the reddening value or the tool automatically adjusts the continuum? If I have understood that correctly, SNID works offline, without a web connection. I'd like to install but I'm not know the Linux environment, I wonder if I could use it on Windows OS using a virtual machine.

SNID "flattens" the spectra, effectively removing the continuum before measuring the correlation so extinction effects are eliminated and the program is just looking for matching features. (The spectra I posted are with continuum but you can also view the flattened spectra in SNID.) SNID then lists all the library spectra with a correlation over a certain threshold (a factor called rlap), looks which type (and sub type) the majority of these spectra are and reports this as the type if there is a clear majority of a particular type. You can see a typical example run in the manual here (section 3)
https://people.lam.fr/blondin.stephane/ ... howto.html
There are a lot of parameters which can be altered in the program but I just run with the default.

I am using an old spare laptop with a clean Ubuntu installation. (I am very impressed with how easy installing Ubuntu was. It ran without problems including wireless networking which I use to swap files with the windows laptop.) The installation instructions for SNID are quite good and I got it running after a bit of trial and error and some silly mistakes, not knowing much about linux, fortran compilers etc (I have also installed IRAF but I have yet to try using it)

Cheers
Robin

Le spectre de la SN ce soir (commencé à 25° jusqu'à ~35°).
Il est bien moins intense dans le bleu...
Gelato indique une relation : Type Ib/c mais ça ne colle pas avec les phases.
http://p0.storage.canalblog.com/04/72/7 ... 952792.fit

Hi Robin, thanks a lot for the information. I'll try to install Linux/SNID on an old netbook.

Etienne, there was a very quick change. Blue intensities usually decrease over time but I thought that this was more slowly. Interesting to follow. It seems that P-Cygni Ha absorption is more evident now.

Paolo

Hello Paolo,
Exactly, i think it's strange this decrease in the blue.... I try to follow as soon as possible.

Hi,

here is the spectrun I could take this last night. As Etienne, I have also noticed the decreasing intensity in blue wavelenghs. Apart from this one, very few details can I see. GELATO also gives me a Type-II supernova, more likely a IIL-type, but the fit strenght is low.

Photometry observers noticed that the supernova is still brightening. I'll wait some days to take another spectrum. It's not easy with my telescope, due to the low S/N relationship and the huge light pollution I "enjoy" in the East sky.

Best regards,
Fran

I was able to get just 10min exposure time on this object last night before the clouds arrived. It is a bright target for the modified ALPY 200 though so it was enough to get a good low resolution spectrum.
SNID is confident it is a type IIP near maximum light. Here is the best fit
(It looks like SNID still applies some sort of adjustment to the continuum to match the two spectrum when plotting)

GELATO cannot decide on the sub type but the best fit is a IIP 6 days old
The spectrum has changed significantly around 4500A compared with the BAO spectrum on TNS. The broad line there has gone. This is similar to what was seen in at this time in sn199gi for example
The absorption component of the H alpha P Cygni profile is clear in my spectrum now and gives a blue shifted velocity of -11600km/s compared with the expected H alpha wavelength in the galaxy frame of reference.

Cheers
Robin