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ATLAS have announced an interesting transient in a nearby (4Mpc) galaxy NGC 4631.
https://www.wis-tns.org/astronotes/astronote/2021-33
It was discovered yesterday at mag 18.1 which at this distance gives an absolute magnitude of -10. It could be a nova but this would make it at the high luminosity end. It is embedded deep in the galaxy and looking at the discovery image it would be a tough imaging target at the moment and well out of range of amateur spectroscopy but if it turns out to be a supernova on the rise it could get much brighter (a type Ia without extinction would reach mag 9 a this distance !)
EDIT: If it is a supernova caught early it should already be much brighter tonight
Robin
That’s a great shot Nick, particularly with that bright moon. (To much haze here. I could not even see the galaxy) It looks like it probably is a supernova then. It depends on extinction of course which could be high given where it is but this might end up being one of the brightest for quite a while.
Here it is from 2021-01-30T23:46:28 against a very lumpy galaxy background. Astrometry matches the quoted position to within 1 arcsec.
My original post, which I’ve deleted, marked the wrong object. The new one is correct but has a later timestamp. Robin’s reply hasn’t violated the rules of causality.
It has now been classified as a probable Luminous Red Nova.
http://www.astronomerstelegram.org/?read=14360
I have to confess I had to look up what that was. Fascinating !
https://ui.adsabs.harvard.edu/abs/2019A%26A…630A..75P/abstract
Robin
That was interesting breakfast reading. The last time I imaged one of these was when V838 Mon erupted 18 years ago. CCDs were much smaller then!
Very interesting reading, and a good picture, I’ve never heard of this class of nova before. I hope you manage to get a spectra, fascinating class of object.
Ron Arbour has asked me to post this message in his behalf:
The object AT2021 recently discovered in NGC 4631 has been classified as a Luminous Red Variable which is a sub group of Intermediate Luminosity Optical Transients. This group included Intermediate Luminosity Red Transients and intermediate Red Novae among others and bridged the gap between Novae and Supernovae. The first discovery and hence archetype of all these objects was discovered by an amateur and member of the Association, namely myself. A paper on the object was published in the Journal.
J.Br.Astron.Assoc. 126, 3, 2016
I remember imaging that with my modified webcam and CCTV camera
http://www.threehillsobservatory.co.uk/astro/astro_image_37.htm
and the spectacular light echo images from the Hubble. I took over where the Hubble left off 🙂
http://www.threehillsobservatory.co.uk/astro/v838Mon_anim.gif
I took this colur image last night in fairly average conditions – in my image it has a blueish tint of a typical supernova.
Peter
For clarification, the object designated AT2021biy has not been classified as a supernova but rather a Luminous Red Nova or Luminous Blue variable:The response to my communication with Andrea Pastorello, one of the authours, is as follows:“This is surely NOT a supernova.I’m not sure 100% it is a LRN or an LBV-outburst, we need to follow it to precisely classify it.It is called *red* because it becomes red (cold) very rapidly, much more rapidly than most transient types, and will reach a mid-M stellar spectral typeafter a few months”.I hope this clarifies why the object appears blue, well shown in Peter Tickner’s excellent colour image. It would be nice to see an image when the object eventually turns red. However that may be very difficult as it could be quite faint.Indeed, as I already reported
https://britastro.org/comment/10041#comment-10041
I never said it was a supernova and posted the classification as soon as it became available
Cheers
Robin
I think we can agree though it has indeed turned out to be a “Potentially interesting transient in NGC 4631″
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