Potentially interesting transient in NGC 4631

Forums Deep Sky Potentially interesting transient in NGC 4631

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  • #574878
    Robin Leadbeater
    Participant

    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

    #583763
    Robin Leadbeater
    Participant

    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.

    #583764
    Nick James
    Participant

    Here it is from 2021-01-30T23:46:28 against a very lumpy galaxy background. Astrometry matches the quoted position to within 1 arcsec.

    #583765
    Nick James
    Participant

    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.

    #583766
    Robin Leadbeater
    Participant

    I thought I was going crazy for a moment there replying to imaginary posts !

    #583768
    Robin Leadbeater
    Participant

    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

    #583769
    Nick James
    Participant

    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!

    #583770
    Daryl Dobbs
    Participant

    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.

    #583771
    Jeremy Shears
    Participant

    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

    #583772
    Robin Leadbeater
    Participant

    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

    #583775
    Nick James
    Participant

    Really nice animation although I can see the difference between Hubble and your setup…

    #583776
    Nick James
    Participant

    Yes, a very impressive achievement from Ron.

    #583792
    Peter Tickner
    Participant

    I took this colur image last night in fairly average conditions – in my image it has a blueish tint of a typical supernova.

    Peter

    #583799
    Ron Arbour
    Participant
    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 type
    after 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.
    #583800
    Robin Leadbeater
    Participant

    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

    #583801
    Robin Leadbeater
    Participant

    I think we can agree though it has indeed turned out to be a  “Potentially interesting transient in NGC 4631″ 

    #583802
    Robin Leadbeater
    Participant

    The light curve of some of these objects bounces back though as they redden as the reference I posted shows so it would be interesting to take a comparison image in a few months time

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