2020leu - Supernova in NGC 5363

Re: 2020leu - Supernova in NGC 5363

Postby Robin Leadbeater » Thu Jun 04, 2020 4:33 pm

Oh dear this one refuses to die !
Despite Stan Howerton pointing out that AT2020leu is likely a star, it has now appeared again in TNS under a different name
https://wis-tns.weizmann.ac.il/object/2020lrn.
The object in question is clearly seen in the archive PS-1 image displayed in TNS and the discovery image posted there also confirms it is the same object.

Robin
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Re: 2020leu - Supernova in NGC 5363

Postby Robin Leadbeater » Thu Jun 04, 2020 10:50 pm

Robin Leadbeater wrote:Oh dear this one refuses to die !


Stan Howerton has now posted images against AT 2020lrn showing the "supernova" present in a previous image of his from 2001.
https://www.flickr.com/photos/146026104@N07/49952571956
He also mentions that it was previously erroneously identified as "supernova 1987H" . I found an interesting report of this "discovery" on supernova hunter Robert Evans website here
https://revivalsresearch.net/searchingforsupernovae.php
under "How to make mistakes with a larger telescope" about half way down

Cheers
Robin
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Re: 2020leu - Supernova in NGC 5363

Postby Peter Velez » Sat Jun 06, 2020 12:59 am

Thanks Robin

Its good to see that I am not the only one who was misled.

The images that Stan Howerton has posted are very helpful - it was indeed the object I was trying to image.

Your initial diagnosis was also correct - I had taken a spectrum of the galaxy itself rather than the foreground star. I attach a plot of my "SN" spectrum against a K3V spectrum. The K3V spectrum is shifted by 1129km/s - roughly 20 Angstroms. Both the Mg triplet and the Na line match up well to my spectrum. I've marked these on the plot. Feel free to critique.

I'm now keen to dispel this misconception of the foreground star as a SN by taking a decent spectrum of it. Once the moon goes away, I'll revert to this target.

Pete
Attachments
NGC_5363_compare to K3I_Mg and Na.png
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Re: 2020leu - Supernova in NGC 5363

Postby Peter Velez » Sat Jun 06, 2020 1:06 am

BTW - I have been using both ISIS and Demetra to reduce the data I have collected so far. Its fair to say that the results are not consistently identical. I expect this is largely a result of the learning curve which I am navigating at the moment. I find it harder to remove sky background in Demetra which is why some of my spectra have very suspect emission lines. For binned images, the calibration achieved in ISIS is more suspect. The process to produce a response curve also yields different results.

So at this stage, I wouldn't accept the continuum of my spectra as necessarily reflective of the target at this stage. This is why the overall shape of my spectra and the K3V Pickles data are not the same. That said, I am confident of the absorption lines which fit quite well in my view

Will post about this on the Software part of the forum soon.

Pete
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