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More on the Betelgeuse occultation here: https://www.astronomerstelegram.org/?read=16374
An A&A preprint on arXiv today by a group of astronomers, including Mike Bode of LJMU, discusses “Accretion in the recurrent nova T CrB: Linking the superactive state to the predicted outburst”, https://arxiv.org/abs/2312.04342
Whilst making no specific prediction for the outburst beyond “in the coming year”, they discuss the 2016 – 2023 superactive state and the current pre-eruption dip and how these relates to the impending thermonuclear runaway.
Another year on: now 4 years from the Great Dimming!
An A&A preprint appears on ArXiv today (https://arxiv.org/abs/2312.02816) shows how different layers in the star’s photosphere appeared pourturbed during the event, returning to normal in 2022.
The Great Dimming of Betelgeuse: the photosphere as revealed by tomography during the past 15 years
Daniel Jadlovský, Thomas Granzer, Michael Weber, Kateryna Kravchenko, Jiří Krtička, K. Andrea Dupree, Andrea Chiavassa, G. Klaus Strassmeier, Katja Poppenhäger
Betelgeuse, a red supergiant star of semi-regular variability, underwent a historical minimum of brightness in February 2020, the Great Dimming. Even though the brightness has returned to the values prior to the Great Dimming by now, it continues to exhibit highly unusual behavior. Understanding the long-term atmospheric motions of Betelgeuse and its variability could be a clue to the nature of the Great Dimming and the mass-loss process in red supergiants. Our goal is to study long-term dynamics of the photosphere. We applied the tomographic method, which allows different layers in the stellar atmosphere to be probed in order to reconstruct depth-dependent velocity fields. The method is based on the construction of spectral masks by grouping spectral lines from specific optical depths. These masks are cross-correlated with the observed spectra to recover the velocity field inside each atmospheric layer. We obtained about 2700 spectra during the past 15 years, observed with the STELLA robotic telescope in Tenerife. We analysed the variability of 5 different layers of Betelgeuses photosphere. We found phase shift between the layers, as well as between the variability of velocity and photometry. The time variations of the widths of the cross-correlation function reveal propagation of two shock waves during the Great Dimming. For about 2 years after the Dimming, the time scale of variability was different between the inner and outer photospheric layers. By 2022, all the layers seemingly started to follow a similar behavior as before the Dimming, but pulsating with higher frequency corresponding with the first overtone. Combination of the extensive high-resolution spectroscopic data set with the tomographic method revealed the variable velocity fields in the photosphere of Betelgeuse, for the first time in such detail.
SN 2023ixf gets quite some coverage in today’s pre-print “Supernovae in 2023 (review): breakthroughs by late observations” on ArXiv: https://arxiv.org/abs/2311.17732
Focus is on pre-SN properties of this CCSN.I was looking at the LC the other day and it is rising a bit, but I think this is due to the ellipsoidal modulation associated with the orbital period: 227 days, or half that peak to peak, ca 0.2 to 0.3 mag amplitude . This modulation is superimposed on the overall fading trend do to the pre-eruption Peltier dip.
Hello Paul,
Yes, indeed, John Toone has prepared a NE chart and sequence here: https://britastro.org/vss/xchartcat/CrB%20T%20025.04%2050d.JPG
When it erupts, it will transform this part of the sky – briefly. As I comment in the forthcoming October Journal, I dearly hope the eruption is detected by an amateur astronomer.
John has also extended the sequence at the faint end this year, given that T CrB is in the pre-eruption Peltier dip and is currently fading: https://britastro.org/vss/xchartcat/CrB%20T%20025.04%202d.JPG
Go well,
JeremyThey 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:
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.
Interesting spectroscopy data, Robin. Thanks!
It’s going to get increasingly hard to observe, so your latest spectrogram is welcome.Super to hear that the meeting recordings were successful, Andy. Thanks for all your efforts to achieve this including spending 16.5 hours on buses for the VSS! I am sure people will enjoy watching the talks online when they become available later in the month.
Yesterday’s meeting featured a superb line up of speakers. I’d like to thank them all for highly informative presentations. It was wonderful to be back at the Northamptonshire Natural History Society, thanks to Nick Hewitt (and his team that put on a delicious spread at lunch and kept us well supplied with tea and coffee throughout the day). The number of attendees exceeded our expectations and it was great to see old and new faces.
Here’s a pic (by James Dawson) of the speakers and organisersAttachments:
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.Just a reminder that there is only one week to go until the BAA VSS meeting at Northampton: Saturday September 2.
We have a full line-up of interesting talks for the day. The full programme can be viewed here: https://britastro.org/event/variable-star-section-meeting-2
All the speakers have confirmed they can attend, in spite of the rail strikes, plus we have an additional short talk.
I look forward to welcoming many of you at the meeting next Saturday.
Jeremy Shears
Director, VSSSorry 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.
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.I think Andy has hit the nail on the head here. We really do need more people standing for elected positions, as well as volunteers supporting the breadth of our activities, to ensure our Association thrives. I don’t see how not having ballots is going to help that. If anyone thinks they’d like to stand at the next ballot, or volunteering in any capacity for that matter, now’s the time to start exploring the possibility.
Whilst BBQs might be popular in Essex, up here in the north I have used a chimenea cover.
In the past I have used an upturned dustbin, as suggested by David, tho this was for a smaller mount. The EQ head was on a pier which passed through the dustbin lid, allowing the lid to be attached to the inverted bin thus providing more protection.
There is a charming article about the discoverer of SN2023ixf in the journal Science:
https://www.science.org/content/article/amateur-astronomer-may-worlds-top-supernova-hunter
