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Great stuff, Richard.
The canonical theory is that the secondary transfers mass to the white dwarf and at a certain point sufficient material builds up on the surface of the WD to trigger a thermonuclear runway. The problem, of course, is we don’t know how far away from that point we are as we cannot measure it.
It will all become clear with hindsight and this time round we will have the most detailed understanding of the events immediately before and after the eruption to post rationalise it all. At least we now have an additional datapoint from 1946 thanks to Michael Woodman.
I’m meeting Brad Schaefer in November and it will be interesting to hear his latest thinking.
In my last reply, the link to the paper by Schaefer on the historical outbursts of T CrB got mangled. It should be:
https://ui.adsabs.harvard.edu/abs/2023JHA….54..436S/abstract(I tried to edit the link 3 times, but each time it got mangled…)
And mangled again! Try this
Richard, the 2024.4 (+/- 0.3) estimate does not come from Brad’s analysis of the intervals from these earlier eruptions, but from a comparison of the light curve over the last ~10 years with that leading up to the 1946 eruption. They show common features, like a “super active state”, pre-eruption dip. This is described here:
https://ui.adsabs.harvard.edu/abs/2023MNRAS.524.3146S/abstract
And refined here:
B.E. Schaefer, B. Kloppenborg, E.O. Waagen, “Recurrent Nova T CrB Has Just Started Its Pre-eruption Dip in March/April 2023, so the Eruption Should Occur Around 2024.4 +- 0.3,” The Astronomer’s Telegram, No. 16107 (2023). The SAO/NASA Astrophysics Data System.His paper concerning his identification of much earlier outbursts ( https://ui.adsabs.harvard.edu/abs/2023JHA….54..436S/abstract ) says:
“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 nine eruptions from 1217.8 to 1946.1, the average recurrence timescale is 80.9 years.”
So the 78.3 +/-0.3 error bar comes from the first paper, not his analysis of the interval between the 4 known eruptions. This average timescale is 80.9 years (no error bar given).Brad’s predictions are based on his assumption that the next eruption will unfold in the same way as the last two (which appear to have identical light curves). But there is no strong astrophysical reason that this should be the case a third time. As I’ve reported previously, other researchers have made predictions for later in 2024 or even Nov 2025. We shall just have to keep on looking.
I’ve mentioned the independent discovery of the 1946 eruption of T CrB by 15-year old Michael Woodman in recent VSS Circulars.
I’ve recently had the privilege of meeting him and have subsequently written this note in RNAAS, highlighting how his observation helps to fill in our understanding of the early stage of the eruption:
https://iopscience.iop.org/article/10.3847/2515-5172/ad7ba8
I very much hope he will have the opportunity of seeing the next eruption, whenever that might occur.
Go well!
JeremyA paper submitted to AAS Journals and published on ArXiv today considers whether Betelgeuse might have a tiny companion.
The paper titled “Radial Velocity and Astrometric Evidence for a Close Companion to Betelgeuse” is at: https://arxiv.org/abs/2409.11332Hello Ian, the abrupt drop in R ~1.4 mag last week is intriguing. I presume reduction in H-Alpha emission. Be interesting if there are spectra from around the same to see what’s happening there. Jeremy
Following on from Steve Brown’s image of the field of chi Cyg, https://britastro.org/observations/observation.php?id=20240906_212805_d660b28088bb3616, here is the recent light curve of chi. It was at maximum of ~mag 4.2 in early July and is now fading.
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Since March 2024, RW Cep has started dimming again as shown in the VSS light curve
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An ApJL pre-print “Time-Evolution Images of the Hypergiant RW Cephei During the Re-brightening Phase Following the Great Dimming” appears on ArXiv today: https://arxiv.org/abs/2408.11906
This is a follow-up on the 2022 December Great Dimming episode. The authors present analysis of the re-brightening during 2023. They demonstrate that the west side of RW Cep, initially obscured during the dimming phase, reappeared during the subsequent re-brightening phase and the diameter became larger by 8%. They suggest that the dimming of RW Cep was a result from a recent surface mass ejection event, generating a dust cloud that partially obstructed the photosphere.
It is interesting to see that they present a light curve from 1900 to 2024, and other analyses, which to a great extent relies on amateur observations (from the AAVSO database, which encorporates data from the BAA VSS). This shows the value of long term amateur observations.
RW Cep can readily be monitored with binoculars as it varies between mag ~6.2-7.8 We have obs in the BAA VSS database going back to 1969 made by:
S W Albrighton, C M Allen, M Barrett, B J Beesley, M R Bell, P Bibbings, N M Bone, A Brown, P R Clayton, M Currie, H J Davies, D Dobbs, S J Evans, G Fleming, R B I Fraser, V J Freeman, A Gardner, M Glennon, A Good, T Gough, B H Granslo, D Hale-Sutton, M A Hapgood, W Harris, C Henshaw, T L Heywood, P W Hornby, R K Hunt, G M Hurst, J E Isles, B Jobson, S Johnston, S Koushiappas, M Long, T Lubek, B MacDonald, C Mann, T Markham, L McCalman, I A Middlemist, I Miller, P Mulligan, I P Nartowicz, C Newman, M J Nicholls, W Parkes, J Parkinson, R Pearce, D A Pickup, G Pointer, M Poxon, P Quadt, G Ramsay, D W Robinson, T G Saville, D R B Saw, A Smeaton, D M Swain, M D Taylor, G Thompson, J Toone, C Watkins, J Whinfrey, N White, G Winstanley, J D Wise, W J Worraker, E Yusuf
I’ve updated the website article on observing T CrB with the latest info: https://britastro.org/section_news_item/get-set-for-the-next-eruption-of-the-recurrent-nova-t-coronae-borealis
Good to see this coverage of UZ Boo and especially to see the appearance of SH’s. Hopefully these will grow.
The sky here last evening was dreadful: I could only see Vega, Altair and a very coppery Moon.No real updates on Brad’s prediction of the eruption during his webinar. His best prediction is based on fitting the light curve from ~2015 to now with the light curve leading up to the 1946 eruption which gives 2024.4 +/- 0.3. He reckons we are at, or near, the bottom of the pre-eruption dip. He was saying the eruption could therefore be any day now, as we are still in his predicted Feb to Sep window. It could also be in the next weeks or months, but likely before the end of the year.
Brad also discussed his analysis of the intervals between the 4 known eruptions (1946, 1866, 1787, 1217), which leads to ~2024.7 for the next one, i.e. ~ September.
So far it has followed a pretty linear decline. Well worth continuing to watch.
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These are fairly small variations, Magnus, so it might be that superhumps haven’t started yet if the outburst is still in its early stages. In previous superoutbursts, orbital humps (~0.1 mag amp) appear first, followed by larger superhumps after ~3 days. Definitely worth following over the next nights.
Invitation to Brad Schaefer’s Zoom talk on August 17th regarding the predicted eruption of T CrB
I am sharing this invitation from Edwin Aguirre about this Zoom talk on August 17 (Saturday) at 1:30 p.m. UTC (14.30 BST)
It will be interesting to hear his prediction for the time of the eruption.Jeremy
I would like to invite you and the BAA members to Brad Schaefer’s Zoom talk on August 17 (Saturday) at 9:30 a.m. EDT (1:30 p.m. UTC) regarding the anticipated eruption of T Coronae Borealis. The talk is free and open to the public.
Attached are the details of Brad’s online talk. In addition to Zoom, the event will be streamed on Facebook Live and recorded for YouTube viewers.
NOTE: Everyone needs to register first in order to get the Zoom link for the webinar. You can either scan the QR code on the attached announcement with your cellphone or go directly to the Zoom registration page:
https://us02web.zoom.us/webinar/register/WN_Bm_NLfhkSQyG0Es31OYkqg#/registration
Brad’s talk is part of the “Astronomy Experts Speaker Series” that Imelda and I started two years ago in collaboration with the Astronomical League of the Philippines. As you know, the Philippines is a relatively small developing country in Southeast Asia, and many people there cannot afford to travel overseas to attend astronomy seminars and conferences.
So, our goal is to help raise public science literacy and awareness in the country by inviting renowned scientists, researchers and science communicators to share their knowledge and expertise online with the Filipino people through our Zoom webinar series. It is all part of our international astronomy educational outreach efforts.
To date, our guest speakers have included:
Prof. Jay Pasachoff (Williams College), who talked about his 2021 Antarctic solar eclipse expedition
Zolt Levay (STScI), who discussed the Hubble Space Telescope’s most iconic images
Dave Eicher (Astronomy magazine editor-in-chief), who spoke about galaxies and galaxy classification
Fred Espenak (Mr. Eclipse), who talked about predicting and chasing total solar eclipses
J. Kelly Beatty (Sky & Telescope magazine senior editor), who spoke about the fight against light pollution
David Levy on how he and the Shoemakers discovered Comet Shoemaker-Levy 9
Heidi Hammel (AURA vice president for science), who spoke about the James Webb Space Telescope’s latest findings
Dan Green (CBAT director), who discussed the nature of comets
Debbie Elmegreen (IAU president), who talked about galaxies at the dawn of the Universe
Father Chris Corbally, S.J. (Vatican Observatory/Steward Observatory), who explained the mystery of “The Star of Bethlehem”
Brother Robert Macke, S.J. (Curator of the Vatican Observatory’s meteorite collection at Castel Gandolfo, Italy), who talked about meteorites, asteroid 101955 Bennu, and the OSIRIS-REx mission
Brother Guy Consolmagno, S.J. (Vatican Observatory director), who talked about Vesta and the Dawn mission
Valentin M. Pillet (National Solar Observatory director), who discussed the solar corona and the current Solar Cycle 25
Mike Brown (Caltech), who talked about Pluto and the search for Planet Nine
Robert Nemiroff (Michigan Tech), co-founder and editor of NASA’s Astronomy Picture of the Day (APOD)
Jonathan McDowell (Harvard-Smithsonian Center for Astrophysics), who spoke about the Chandra X-ray Observatory and the invisible Universe.
For fall/winter, we plan to have Meg Urry (Yale University), who will talk about the supermassive black hole lurking at the center of the Milky Way, and Michael S. Kelley, program scientist for the Planetary Defense Coordination Office at NASA Headquarters, who will discuss the impact threat posed by NEOs, and for next year, NASA astronaut Don Pettit, who will talk about astrophotography from the International Space Station. We are currently finalizing the schedules for their respective webinars.We hope you can join us for Brad’s talk on the 17th!
Best regards,
Edwin
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Fascinating details in the light curve you are picking up in your photometry, Ian! Intriguing slow rise during quiescence, followed by a drop leading into the next outburst.
