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Supernova SN2023ixf in M101 - How to measure brightness?

Processing Photometry Deep Sky Supernova M101
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Christian Koll avatar
Christian Koll avatar
Hello,

I recently read in an article that the supernova in M101 (SN2023ixf) is to date the most observed supernova in history and that amateurs provided a huge amount of data to plot the brightness curve.

I do have a very nice image of that event that was taken only 3 days after the supernova was discovered by Koichi Itagaki:
https://www.astrobin.com/0jk01n/C/

I am wondering what is the state of the art method for deriving the brightness from RAW data?
I do know how to extract an approximate value comparing the brightness to other stars in the frame - but I'm not sure if this is scientifically correct.

I do have exposures in L, R, G and B - I suppose only the luminance is the one to measure?
Where can I enter my brightness values for scientific consideration and what other things do I have to provide/bear in mind?

Any help is greatly appreciated!
Chris
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Martin Mančuška avatar
Martin Mančuška avatar
Hi Christian,

if you are asking for photometry of the star I recommend you to take a look on AAVSO  and their manual for DSLR observing of variable stars: https://www.aavso.org/dslr-camera-photometry-guide.
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Ian Sharp avatar
Ian Sharp avatar
Hi Christian,

I've been measuring the brightness of SN2023 ixf since it exploded in R, V and B filters (see graph). I use AstroArt for the photometry but there are many other tools available. I would recommend the AAVSO website where there is a tool called VPhot. Also the TychoTracker is brilliant. If you have MaximDL you can used that. Also you can use ASTAP which is free. The AAVSO guide is excellent but detailed.

You will need to make sure the Sn itself and any comparison stars are not saturated in you images.

Lots to learn!


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Ben Koltenbah avatar
Ben Koltenbah avatar
That's a great, dedicated project, Ian!  Well done!  It's neat to see data from the three color filters.

Chris, I measured the magnitude using my luminance filter during the SN's rapid brightening phase a few hours before its discovery, although I didn't become aware of it until after the announcement.  Here are my results.  I describe my method in my original post if you are interested.



Best Regards,
Ben
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Ian Sharp avatar
Ian Sharp avatar
Excellent!
Cheers
Ian
Ulli_K avatar
Ulli_K avatar
Hi
I could only make a few measurements of the SN brightness SN2023 ixf
The brightness was determined by measuring the flux of a series of stars in PI. I measured the magnitude in the stacked linear image using PI AperturePhotometry. I used the flux data and calculated the magnitude using the equation mag1 = mag - 2.5*log10(flux1/flux2) where mag1 and flux1 are the data of the supernova, while mag2 and flux2 are the values of the reference stars. The same way I did it for SN 2022 hrs.

CS, Ulli
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Ulli_K avatar
Ulli_K avatar
Hi @Ian Sharp 
how did you manage to measure the brightness over such a long period of time?
Cs, Ulli
Ian Sharp avatar
Ian Sharp avatar
Hi @Ian Sharp 
how did you manage to measure the brightness over such a long period of time?
Cs, Ulli

I just keep on imaging it! I have telescopes in the UK and a remote setup in Spain. It is clear here in the UK at the moment, so I will image it from here again tonight. The weather in Spain is not so good tonight.

Ian.
Ruben Barbosa avatar
Ruben Barbosa avatar
Hi Christian,

I already measure the magnitude of a SN with MaxImDL.

It's quite simple. Basically, it's as you said, by comparison with another star of known brightness.
However, you must pay special attention to the fact that your star cannot be saturated. This means that you must be able to make a Gaussian curve with the brightness (Maximdl does this too), otherwise the result will be wrong.

Good luck.
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