Recurrent nova in M31 - M31N 2008-12a

[Xilman]

Anyone who wishes to image a recurrent nova on M31 ought to plan to do so within the next day or few. It erupts with a period of about 12 months and has been visible since at least 2023 Dec. 05.54775 UTC. Discovery announcement in this ATel   https://www.astronomerstelegram.org/?read=16361.  Note that 120 seconds on a 0.5m telescope puts it well within range of most amateur equipment.

Nick James of the BAA-VSS has produced this image. Coordinates are given in the image, as are the magnitudes for four sequence stars. Any photometry will be valuable.

 

[Elp]

Intrigued by this, would these not be present in images prior to December 2023?

[Xilman]

12 hours ago, Elp said:

Intrigued by this, would these not be present in images prior to December 2023?

The NR has a very short eruption period.  It wasn't visible 24 hours before that image was taken. It will likely have fallen below magnitude 21 within 3 or 4 days. If you want to see it, you have to be quick.

 

[Elp]

I assume their FWHM may change slightly? I ask because three or four of the red ones I think I've captured in my stacks, one of which was done before December.

[Elp]

Alas, the blue one I haven't imaged.

[Xilman]

5 hours ago, Elp said:

I assume their FWHM may change slightly? I ask because three or four of the red ones I think I've captured in my stacks, one of which was done before December.

FWHM? I do not understand. The outburst rises from below mag 23 to maximum - typically 17.5 - in less than a day. If you do not image it in the next 2-3 days it will too faint for you to do so.