Preparing for the eruption of T CrB

Forums Variable Stars Preparing for the eruption of T CrB

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  • #618815
    Jeremy Shears
    Participant

    I’ve put an article on the website about the next eruption and how to observe this star NOW: https://britastro.org/section_news_item/get-set-for-the-next-eruption-of-the-recurrent-nova-t-coronae-borealis.

    We can use this thread to provide updates.

    We don’t know exactly when T CrB will erupt and we will doubtless see various predictions as the light curve becomes better defined over the next weeks. Currently, Prof. Bradley E. Schaefer (Department of Physics and Astronomy, Louisiana State University) suggests 2024.4 ± 0.3, i.e. 2024 February to August. A paper from a team at the Sternberg Astrophysical Inst, submitted to Astronomy Letters appeared today, offering their prediction for the eruption: January 2024, https://arxiv.org/abs/2308.10011

    As the year progresses, the field of T CrB will become harder to observe, but it is important that observations continue.

    #618839
    Mr Ian David Sharp
    Participant

    Hi Jeremy,

    I’ve been monitoring T CrB for a couple of months in R, V and B and have noticed much more variability in B, but it has not made any significant shifts until last night when I managed a longer run over about 2 hours. See the attached graph.

    The problem I have so far is that my reference and check stars are a good 2 mags. fainter because of the tight FOV of my C11 setup. I’ll try and offset the FOV a tad to fit in a brighter ref star or two.

    Cheers
    Ian.

    #618852
    Jeremy Shears
    Participant

    Thanks sharing your data Ian. That’s quite a change!It will be interesting to see what it does next.
    Indeed, flickering type variations are more prominent in B.

    #618871
    Mr Ian David Sharp
    Participant

    Thanks Jeremy,

    I managed to get an 11th mag comparison star in the FOV and that has improved things.

    Here’s another 2 hour B run from last night.

    Cheers
    Ian.

    #618873
    Paul G. Abel
    Participant

    Well I’ve now lost it from my observatory so I can guarantee that it will now do something interesting!!

    #618878
    Jeremy Shears
    Participant

    Sorry to hear you’ve lost sight of the field of T CrB, Paul. For many it will become harder to follow as the autumn progresses, which is why it’s important for anyone that is able to access the field to continue to observe it. Towards the end of the year it becomes accessible in the morning.

    I very much hope that an amateur detects the eruption- last time, 1946, it was two British observes that caught it, one a member of the BAA Variable Star Section.

    #618908
    Jeremy Shears
    Participant

    A post not about the next eruption, but about two previous ones in 1787 and 1217!

    A JHA pre-print by Prof Brad Schaefer The recurrent nova T CrB had prior eruptions observed near December 1787 and October 1217 AD appears on ArXiv today: https://arxiv.org/abs/2308.13668

    He comments “T CrB has four observed eruptions in the years 1217.8, 1787.9, 1866.4, and
    1946.1, plus one more expected upcoming in 2024.4±0.3. The recurrence
    timescales are 7×81.4, 78.5, 79.7, and likely 78.3±0.3 years. With 9 eruptions
    from 1217.8 to 1946.1, the average recurrence timescale is 80.9 years. I expect
    additional eruptions within a year or two of 1706, 1625, 1544, 1462, 1381, 1299,
    1137, 1055, 974, 892, 811, 730, 648, 567, 485, 404, 323, 241, 160, and 78 AD. ”

    Abstract:
    The famous recurrent nova (RN) T Coronae Borealis (T CrB) has had observed eruptions peaking at a visual magnitude of 2.0 in the years 1866 and 1946, while a third eruption is now expected for the year 2024.4+-0.3. Each RN has very similar light curves of eruptions that come with a fairly even-spacing in time, for which T CrB has a recurrence timescale near 80 years. So it is reasonable to look backwards in time for prior eruptions, around 1786, and so on back. I have investigated two long-lost suggestions that T CrB was seen in eruption in the years 1217 and 1787. (1) In a catalog published in 1789, the Reverend Francis Wollaston reports an astrometric position for a star that is exactly on top of T CrB. From his letters, these observations were made on at least four occassions with both a large and small telescope, within a few days before 1787 December 28. Wollaston’s limiting magnitude for his astrometry is near 7.8 mag, so T CrB would have to have been in eruption. With other transients strongly rejected, the only way that Wollaston could get the coordinates was to have measured the coordinates of T CrB itself during an eruption. (2) The 1217 event has an eyewitness report written by Abbott Burchard of Upsberg as a fast-rising stellar point-source (“stella”) in Corona Borealis that “shone with great light”, lasted for “many days”, and was ascribed as being a “wonderful sign”. This event cannot be a report of a comet, because Burchard used the term for a star (“stella”) and not for a comet, and because Burchard had the omen being very positive, with such being impossible for comets that are universally the worst of omens. The reported event is just as expected for a prior eruption of T CrB, and all other possibilities are strongly rejected, so the case for the 1217 eruption of T CrB is strong.

    • This reply was modified 10 months, 3 weeks ago by Jeremy Shears.
    • This reply was modified 10 months, 3 weeks ago by Jeremy Shears.
    #619006
    Robin Leadbeater
    Participant

    I managed to squeeze in a high resolution spectrum last night in twilight before it dipped into some trees. The decreasing Equivalent Width of the H alpha emission line reported in ATel #16214
    https://www.astronomerstelegram.org/?read=16214
    is confirmed by the spectra in the BAA database.

    Cheers
    Robin

    Attachments:
    #619008
    Jeremy Shears
    Participant

    Interesting spectroscopy data, Robin. Thanks!
    It’s going to get increasingly hard to observe, so your latest spectrogram is welcome.

    #619010
    Robin Leadbeater
    Participant

    The He 6678 line (which I understand is more sensitive to changes in the inner disc region) has disappeared into the noise in my spectrum

    • This reply was modified 10 months, 2 weeks ago by Robin Leadbeater. Reason: trying again to attach file
    • This reply was modified 10 months, 2 weeks ago by Robin Leadbeater.
    Attachments:
    #619015
    David Boyd
    Participant

    This LISA spectrum of T CrB taken on 4th September shows that emission lines other than H alpha and to a lesser extent H beta have disappeared at this resolution.

    David

    #619037
    Alex Pratt
    Participant

    Special Webinar: Recurrent Nova T CrB Coming Soon to a Sky Near You – Dr. Brad Schaefer, Professor Emeritus of Physics and Astronomy at LSU

    https://us02web.zoom.us/webinar/register/8116929086840/WN_Pn59ESvzQOiSQzLHULi4Ig#/registration

    • This reply was modified 10 months, 2 weeks ago by Alex Pratt.
    #619066
    Jeremy Shears
    Participant

    One research question Brad Schaefer raised was whether T CrB is a Neon nova. A spectrum from the 1946 eruption suggested it might be. If it is, then it is not a Type 1a SN progenitor. Hence Brad encouraged spectroscopists to look for the appearance of Ne III lines (3869 and 3965 A) 1 week to 1 month post peak eruption.

    #619082
    Maxim Usatov
    Participant

    Is there a recording available of Dr. Schaefer’s webinar?

    #619086
    Jeremy Shears
    Participant

    They said there would be a video available shortly.
    Here is a screenshot of his observing suggestions. He has a special focus on U band photometry as professionals not doing much. Though this wavelength is quite challenging for amateurs. Multicolour (U)BVRI also encouraged.

    Attachments:
    #619090
    Mr Ian David Sharp
    Participant

    They said there would be a video available shortly.

    Here it is: https://fb.watch/mZhv9T6ax3/

    Cheers
    Ian.

    #619094
    Mr Ian David Sharp
    Participant

    Wow! Just been watching Brad Schaefer’s presentation. This is so exciting! Now I understand why the call for B-band photometry.

    Marvellous!

    Ian.

    #619095
    Stewart John Bean
    Participant

    I also watched the webinar last night. I had a look at the TESS data for T CrB later but not too interesting: You see the orbital period and the flickering ( on all timescales). There are only 3 28 day periods that TESS has observed it.

    I found the lack of understanding of the “high state” and “secondary brightening” after 100 days post eruption and interesting.

    Stewart

    #619096
    Michael O’Connell
    Participant

    Really good talk!
    Thanks for sharing Ian.
    Michael.

    #619097
    Alex Pratt
    Participant

    During the webinar, the speaker repeated that “…T CrB will soon be the brightest nova in living memory…at mag 2…” Someone commented in the Chat box that Nova Cyg 1975 (=V1500 Cyg) reached mag ~1.7. (BAA VSS database ~1.5).

    Perhaps he meant the brightest known recurrent nova.

    Many observers enjoyed seeing the ‘new star’ in Cygnus in August/September 1975, including myself, and I look forward to observing T CrB in outburst.

    Alex.

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