M31N 2008-12a call to arms.

Forums Variable Stars M31N 2008-12a call to arms.

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    Dr Paul Leyland

    It is that time of year again. A recurrent nova in M31 is due to go off again. This one has by far the shortest recurrence period known at about 1 year. I have been looking out for it for quite a while but it has never shown up when I am in La Palma. If you subscribe to 12a_Monitoring@googlegroups.com you will have seen the material below. If not, and you can image down to mag 18 or so in a reasonable time (meaning you have a 20cm telescope or larger) please consider subscribing. My http://www.astropalma.com/Projects/VS/M31N_2008-12a.html provides more information and a link to a finder chart.

    Thanks, Paul

    Dear colleagues,

    Another year ticked off (almost)! As always, I hope you are all keeping well at this time!

    Traditionally, this is an e-mail I’ve send around the start of September – this year, I am purposely sending it later as we are working toward a smaller potential eruption window. I know many of you have already been observing 12a regularly – so thanks for that!

    This email is to let you all know that, yet again, we have officially restarted our ground-based optical monitoring of the remarkable M31 recurrent nova M31N 2008-12a with the aim to detect the 2023 eruption. As always, I want to extend our thanks to those of you who have already been observing over the last weeks and I want to encourage everyone to join the monitoring effort once again.

    We have again secured several very early time spectroscopic observations of the 2023 eruption that require early notification of the 2023 eruption for triggering. This again includes time on the Liverpool Telescope. Our aim with these follow-up observations remains to probe the early-time physics that drive the eruption and an attempt to definitively determine the ultimate fate of M31N 2008-12a – whether one day it will explode as a Type Ia supernova or collapse to a neutron star. Your continued involvement in this project is key to all these aims! Each year we manage to get on target faster and faster, we are hoping that the heavens (and weather) align this year to start our follow-up observations within an hour of the eruption occurring – it’s ambitious, but in theory we can do it!

    Last year, although we had an early detection of the eruption of 12a (https://www.astronomerstelegram.org/?read=15786) and rapid spectroscopic follow-up (https://www.astronomerstelegram.org/?read=15788), unfortunately, the geography at the time of eruption meant that we discovered the event just too late to meet the early spectroscopic goals. The LT is setup to automatically trigger spectroscopic observations of 12a as soon as we receive a report of an eruption – stopping any on-going observations at the time, we have ‘ultimate priority’ for these observations! Indeed, we have automated the whole process should the LT be the first telescope to detect the 2023 eruption!

    As in previous years, below I outline in detail the monitoring and reporting structure, as well as the notifications in case of a discovery. This strategy is the same as recent years. Please follow the precise instructions because, for instance, some of us have set up email alerts based on the email subject of the discovery notification.

    In previous years, the Liverpool Telescope has been a regular source of additional eruption monitoring observations but has only been the first telescope to detect three of the fifteen consecutive eruptions (2014, 2018, and 2020). Out of interest, of those 15 eruptions 8 have been detected by members of this group (the other 7 by facilities such as PTF, LT, and LCO)!

    We will still be using the mailing list 12a_Monitoring@googlegroups.com for the communication within the collaboration. The finding chart and reference stars remain the same as for the previous eruption. If you have any questions don’t hesitate to contact me at M.J.Darnley@ljmu.ac.uk and I will provide clarification. Please note that the “12a” mailing list is reserved for discussions about this nova.

    I hope that all of you will join again for another exciting season of watching the most remarkable nova go into eruption. Please let me know in case you will not be able to participate in this year’s campaign.

    Best regards and clear skies,

    Matt for the 12a Collaboration

    1) The eruption date prediction

    Based on an updated analysis, we expect the 2023 eruption of 12a will take place in December 2023, with the window possibly extending into early January 2024.

    2) Who is coordinating

    Mike Healy (M.W.Healy@ljmu.ac.uk) and I (M.J.Darnley@ljmu.ac.uk) will be coordinating the observations, but also involved and very interested will be: Allen Shafter (awshafter@gmail.com).

    3) Communication strategy

    For the communication within the collaboration we will use exclusively the mailing list 12a_Monitoring@googlegroups.com. The usage of the list should be restricted to notifications of (potential) discoveries, status updates from the coordinators, requests for confirmation, and urgent queries. This will reduce the email traffic for all of us. In case of non-urgent/minor questions or updates please contact me (M.J.Darnley@ljmu.ac.uk) directly.

    4) Where to report upper limits and photometry?

    We encourage all of you to report your upper limits to the AAVSO database, whether you are an AAVSO member or not. We have established the AAVSO database as central data collection hub for this project. We will be checking your reported upper limits frequently. Here is information on how to submit data to the AAVSO, courtesy of (former) AAVSO director Stella Kafka:

    Information on how to get an AAVSO observer code and submit your data directly to the AAVSO database: To do so, you need to create an account here: https://www.aavso.org/join-aavso(under “Click Here to Join the AAVSO”).

    Once you register, please request an observer code.

    Please note that you don’t need to be members to get an observer code and submit data (although it would be great if everyone becomes an AAVSO member and supports the association). Observer codes are unique and help us give credit to observers who acquire observations and diagnose problems with discrepant data when needed.

    In case of further questions about the AAVSO data base please contact me (M.J.Darnley@ljmu.ac.uk) or the AAVSO directly.

    5) What do we need for a discovery?

    To discover the eruption and notify the collaboration, you only need a reliable detection. Ideally, the nova should be clearly detected in more than one exposure. Photometry is useful, but can be done later, because we need to react fast. We are relying on your expertise and judgement about whether a detection is real. If in doubt, follow point 7 below.

    Please find attached a finding chart of the nova. The finder chart image is an exceptionally deep exposure taken by the 2m Liverpool Telescope through a Sloan r’ filter, the median seeing of the 21 images combined here was around 1 arcsecond.

    6) Discovery notification

    If you are successful in discovering the eruption, please notify the collaboration immediately through the mailing list: 12a_Monitoring@googlegroups.com

    This should be the first thing you do. CBAT entries or ATels can wait until after this (short) email. Remember that the nova is evolving fast and that we need to be very quick (particularly in triggering the follow-up observations).

    Here is a template for the discovery notification. Please attach a discovery image for your stacked data and for at least 2 individual exposures. Ideally, we need a .fits file but if it speeds up the notification then a .jpg screenshot is fine.

    If you can immediately provide photometry, then please do so. Otherwise send this email without photometry but start working on the photometry after sending. We will get back to you very quickly.




    M31N 2008-12a – 2023 eruption discovered!



    Dear colleagues,

    The 2023 eruption has been discovered. Please try to increase your observing cadence to monitor the light curve.

    The nova was discovered on <date and time> with a magnitude of <mag> at the <observatory>. Discovery images are attached.


    7) If you are not sure

    If you are not sure whether you have discovered the nova, please contact the mailing list (12a_Monitoring@googlegroups.com) to request a confirmation. Attach your discovery image(s) and include (preliminary) photometry as well as the location of your observatory.

    This scenario is meant for low signal/noise detections at the nova position. If in doubt, please send this email. We’d rather have a few false positives then missing the early stages of an eruption.



    M31N 2008-12a – possible 2023 detection; requesting confirmation



    Dear colleagues,

    I found a possible detection of the nova on <date and time> with a magnitude of about <mag> at the <observatory>. Discovery images are attached. Please try to confirm this detection.


    8) Announcement and publication

    The aim is to announce the discovery in an ATel as soon as possible. All photometry will also be included in a comprehensive publication in a refereed journal.

    If you discover the eruption, and after notifying the collaboration, you can publish the ATel yourself or send your discovery information to the following people, one of which will publish the ATel as quickly as possible:




    If you choose to send the ATel yourself, below is a template that you can use (including some html code in the first paragraph that you can just copy and paste). See also the ATel on the 2017—2021 eruptions:






    Nick James

    Thanks for the reminder about this Paul. I’ll register with the email list and will schedule a few runs on this field each clear night through December. I took the attached tonight. No sign of the nova at the moment!

    Nick James

    I think it has appeared. See attached.

    Can anyone confirm?

    Nick James

    Yes, already detected in China a few hours ago: https://www.astronomerstelegram.org/?read=16361

    Dr Paul Leyland

    I regret not being in La Palma.

    Dr Paul Leyland

    Please see https://britastro.org/observations/observation.php?id=20231213_165900_046f8d7b41dfcd8f

    Not as impressive as Nick’s image but the nova had already faded to mag 21 by then.

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