My latest low resolution spectra (below), taken last night (10 Nov) from urban Melbourne shows the strong 'blue' component ... fairly typical of a type 1a.
My latest low resolution spectra (below), taken last night (10 Nov) from urban Melbourne shows the strong 'blue' component ... fairly typical of a type 1a.
Bernard, thanks for posting the spectrum. Looks like good work.
From my reading, I understand the the strong emission in the blue end for type Ia at this point in its evolution is due to the decay of Nickel. This will be the case around peak brightness, as we are seeing the shell.
Weeks and months down the track, the shell will have expanded to transparency, and we will then see the core, which will be less blue.
Quote:
Originally Posted by SkyViking
Thanks for the update Ivan. Impressive with a 11.90 magnitude! If that's in R then I assume B must be even brighter?
I measured the R-band brightness again last night, it was 11.97 +/- 0.03 .. So possibly flat, possibly dimming. However there were thin clouds, so the accuracy can be affected. I think we will need another data point or two before deciding where the peak is.
I have only been measuring R so far, but I think Terry has measured other bands so may be able to give us a comparison.
I took a spectra and photometry last night but haven't reduced them yet. It was very difficult as I had howling wind and even 20s exposures were very difficult. The spectra was fine though. If the star moves off the slit it just reduces the through put and doesn't give trailed images like the photometry images. Hopefully some of the exposures will be ok.
I've found various explanations for the type 1a process ... which is still not fully understood. One says that the decay of NiII, and higher Ni ions, results in heating the expanding shell to very high temperatures -> hence the very blue continuum of the SN remnant. Other sources say it is the decay of 56/27 Cobalt that is responsible.
Normally SN explosions destroy the progenitor star so it is unlikely there will be any core left to see, unlike PNs.
Ha! I pinned the bugger visually! And from home in Sydney.
Man that was hard work. 1365's core is so faint under Sydney's skies. The only way to see it using my 8" f/4 dob was to up the magnification as far as possible. Low power JUST showed a hint of the core. Upping the magnification to 100X was necessary to make out the SN which is brighter than the other foreground stars that accomany it close to 1365's core. Kevin's photo of the area helped me locate and confirm the sighting.
And true to form, as soon as I was confident of the sighting, it clouded over and no chance of a sketch.
Now, if the clouds play ball and bugger off this Saturday...
Glad you found the widefield shot useful Alex. Would you believe I haven't actually seen the SN visually yet. I haven't been able to drag the 10 inch out and I can't see it in the 5 inch.
>Normally SN explosions destroy the progenitor star so it is unlikely there will be any core left to see, unlike PNs.<
I forgot to qualify that statement with the comment that only type Ia SN leave no compact remnant. The other types (Ib,Ic,II) do end up with neutron star, pulsar or black hole cores.
>Normally SN explosions destroy the progenitor star so it is unlikely there will be any core left to see, unlike PNs.<
I forgot to qualify that statement with the comment that only type Ia SN leave no compact remnant. The other types (Ib,Ic,II) do end up with neutron star, pulsar or black hole cores.
Good point Bernard. It seems the theory is that later stages of the lightcurve show emissions from material that used to be the core of the progenitor, now a rapidly expanding shell.
I measured the brightness again last night. It was brighter, at R-band mag 11.88 +/- 0.02 and still rising ever so slowly.
It's lucky to have had so many consecutive nightly sessions! The light curve is coming along nicely.
I took R, B and V photometry on the night of the 13th. Results were:
R = 11.878 +/- 0.020
V = 11.944 +/- 0.018
B = 12.177 +/- 0.028
Brightness seemed to be flat.
I also received a SA100 grating that day, and decided to try it out. My first attempt at a spectrum is attached.
I have roughly guessed the calibration for wavelength and detector sensitivity based on example spectra around, so this is hardly exact, but I think it shows the features you would expect for the Ia supernova.
Excellent progress with your new Star Analyser (SA100) ... now the serious work starts, learning how to process the raw spectral data! While there are a few free, and commercial, software programs that do this task I strongly recommend Buil's free ISIS. http://www.astrosurf.com/buil/isis/isis_en.htm. I've been using ISIS for a number of years and it is constanly improving. I believe Terry also uses it. You also need to subscribe to at least one of the serious (dedicated) spectroscopy groups. I can get you the links if needed.
I'm puzzled by your B magniture being dimmer than the R and V. Given that we know, from spectra, visual and history that this SN has a very strong blue continuum I would have expected B<V<R, not the reverse.
> I took R, B and V photometry on the night of the 13th. Results were:
> R = 11.878 +/- 0.020
> V = 11.944 +/- 0.018
> B = 12.177 +/- 0.028
I can nearly count on the fingers of my two hands the number of imaging nights I've had in the last few months ... I've just been lucky to have had a few of those in the last couple of weeks
I'm puzzled by your B magniture being dimmer than the R and V. Given that we know, from spectra, visual and history that this SN has a very strong blue continuum I would have expected B<V<R, not the reverse.
> I took R, B and V photometry on the night of the 13th. Results were:
> R = 11.878 +/- 0.020
> V = 11.944 +/- 0.018
> B = 12.177 +/- 0.028
Hi Bernard,
I've double checked the images and reference magnitudes, and can't see any error.
Could this be due to the passbands of the Bessel filters? The R filter has a wide passband, and includes a fair bit of V and IR, whereas the B and V filters are quite a bit narrower.
