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Possible Nova in UMa Mag 11.8

PostPosted: Sun May 26, 2019 8:28 pm
by Michel Verlinden
R.A. 10h24m02.89s, Decl. +48°08'51.2" (J2000.0)
2019 May 25.4972 UT, 11.8 mag (CCD, unfiltered)
Discoverer: Tadashi Kojima (Gunma-ken, Japan)
9 mag amplitude
More details here:
https://www.aavso.org/tcp-j102402894808 ... ursa-major
Spectra are welcome.
Cheers.
M. Verlinden

Re: Possible Nova in UMa Mag 11.8

PostPosted: Sun May 26, 2019 9:09 pm
by etienne bertrand
si ça peut aider un champ de l'objet.
Pas le ciel pour moi pour la faire...

Re: Possible Nova in UMa Mag 11.8

PostPosted: Sun May 26, 2019 9:28 pm
by Olivier GARDE
With Pascal Le Dû, we are on the target, but not a good weather in Southern France (many clouds)

Re: Possible Nova in UMa Mag 11.8

PostPosted: Sun May 26, 2019 11:16 pm
by Olivier GARDE
Only one exposure of 600s for this object with bad weather condition (clouds)

Image

So, we don't think it's a Nova .....With bad weather condition, it may have a doubt about the correct positioning of the target, but this is the only star that we can see in the field of view of our guiding CCD with the right magnitude.

Re: Possible Nova in UMa Mag 11.8

PostPosted: Mon May 27, 2019 8:27 am
by etienne bertrand
Bonjour Olivier,
Bravo pour le spectre. C'est curieux qu'est ce qui expliquerait cette baisse de magnitude ?

Re: Possible Nova in UMa Mag 11.8

PostPosted: Mon May 27, 2019 10:45 am
by Robin Leadbeater
Looks like a dwarf nova from the spectrum. (Hot continuum, weak broad Balmer absorption. H alpha very weak/filled with emission?). At mag 12 the progenitor should have been visible in deep images though ?

Robin

EDIT: just looked at the AAVSO reference. There is a probable mag 19 progenitor so ~mag 7 increase, consistent with a dwarf nova

Re: Possible Nova in UMa Mag 11.8

PostPosted: Mon May 27, 2019 11:33 am
by Olivier GARDE
here's Steve's comment on the interpretation of our spectrum :

"This looks like a WD with, perhaps, some emission (Halpha), very little extinction (if any) and a very hot system. The He I lines are weak but there, at least some (4471, 5876, it takes imagination to see 6678), no He II 4686,5411, and otherwise nothing that seems out of the ordinary for a weak cataclysmic. If the emission were stronger I might say it's a polar (or AM Her) but this is definitely not a nova. There's some asymmetry on the Balmer profiles that could be real but, again, nothing particular. If this is an active system, it might have shown some mass loss outburst but there's nothing particular here. Nice spectrum!"

Re: Possible Nova in UMa Mag 11.8

PostPosted: Mon May 27, 2019 1:24 pm
by Robin Leadbeater
Yes, given the progenitor it was unlikely to be a classical nova. (Patrick Schmeer's AAVSO alert was for probable DWARF NOVA, not a nova.) The alert would have been better posted in the cataclysmic variables alert section. Perhaps it can be moved there ?

Cheers
Robin

Re: Possible Nova in UMa Mag 11.8

PostPosted: Mon May 27, 2019 10:51 pm
by etienne bertrand
Un spectre tout frais, on dirait qu'il y a un début de raies d'émission ?
Est ce réel ou est ce du bruit ?
Image

Re: Possible Nova in UMa Mag 11.8

PostPosted: Tue May 28, 2019 11:08 pm
by etienne bertrand
Bonsoir,
Un peu plus de poses sur cet objet :
Image