T CrB near nova outburst

T CrB near nova outburst

Postby Francois Teyssier » Sun Jun 16, 2019 11:48 pm

David Iadevaia has forwarded a message of Brad Schaefer on spectro-l:

From: Brad Schaefer <bradschaefer@me.com>
To: David Iadevaia <davidiadevaia@yahoo.com>
Sent: Friday, June 14, 2019, 8:25:53 PM MST
Subject: Recurrent nova T CrB is just behaving weirdly in its pre-eruption plateau

Hi;

As we discussed I would like to urge you to take many spectra of the recurrent nova T CrB, all leading up to its eruption in 2023.6 +- 1.0. Similarly, you can pass this recruitment around to your colleagues and collaborators, because the more observers the better. This is a wonderful opportunity; (1) because this is a frontline science target well in the range of your spectroscopy (V=10 or so), (2) because the professionals do not know and have not been monitoring the fast moving case, and (3) the nature of the very-high-energy pre-eruption plateau has no theoretical explanation and I could call it ‘impossible’.

It all begins with my >100,000 magnitude light curve, fully corrected to Johnson B and V, from 1842 to 2015:

This shows the 1866 and 1946 eruptions. We see a weird post-eruption plateau and a the still-mysterious second eruption half a year after the first, with the exact same structure being visible after *both* eruptions. We also see a whole complex of unprecedented and un-explained pre-eruption structure before the 1946 eruption. We also see that the light curve from 1955 to 2015 is essentially constant.

OK, let me show you a blow up of the weird stuff around the 1946 eruption. I’ll only show the B light curve as heavily binned in time, and a superposed schematic shape meant to represent a smoothed light curve.
The complex and totally-unique structure after the main peak (and the main peak itself) is identical from 1866 and 1946. This makes us think that the eruption physics will also duplicate the pre-eruption phenomena before every eruption.

OK, now let me update the T CrB light curve from 2015 to present:
Wow, from 1951 until 2014, the light curve has been holding flat, but suddenly in 2015, T CrB starts a determined rise followed by a plateau with a slight downturn. Egad, this is exactly what happened in 1936. The curve superposed is the same template from the 1946 eruption, just shifted 77.5 years. Zounds, this means that T CrB started its pre-eruption plateau in 2014 or 2015. It also means that the next eruption will be in 2023.6 +- 1.0.

Now, the pre-eruption plateau from 1936–1946 has never been published, and every theorist that I’ve talked with has no understanding or even any ideas. I would even say that it is ‘impossible’ for the accretion disk (the undoubted site of the pre-eruption rise) would know that the base of the accreted material on the white dwarf (the undoubted site of the nova trigger) will blow up in a decade.

The pre-eruption plateau in 1936 had a variety of spectra taken and published. You can see a typical paper in the papers attached here:

The ultraviolet continuum if incredibly strong, and there are high-excitation emission lines.

I am acting here as a recruiter and a cheerleader for this perfect frontline amateur spectroscopy program. But I am not theoretically knowledgeable enough, nor do I have substantial experience at analysing spectra. So I am not the person to help you with this large and long program. I’m not even sure who to suggest turning to for guidance and analysis.

The old data is pitiful by modern standard. And that is where you can do greatly better than the heros of old. What is needed is many digital spectra throughout the complex developments of T CrB. You can provide wonderful very-high resolution spectra showing the detailed line profiles, and this will be critical for working out the flows of material inside the system. For this, you’ll need spectra throughout the orbital period to get the Doppler shifts from many directions, and frequently to monitor the changes. The professionals are not doing it, but this is close to your sweet spot.

Cheers,
Brad


Further comments from Brad Schaefer


I appreciate that your group has already long ago started on T CrB. With this, I know that nothing has been missed.

I urge you to redouble your efforts for T CrB, elevating it above just being one-of-a-lon- list-of-standard-targets. You might try to get people to push as far into the ultraviolet as possible, as there are some interesting lines well below 4000 Å. I can hope that you push into the solar gap, so that the Doppler shifts in the line profiles can be measured from many angles around its orbit. Indeed, for a middle-latitude northern observatory, T CrB can be recorded even through its solar conjunction, yielding full year-round measures.

I urge you to make sure that your spectra get published in full, with big tables of eqivalent widths for all lines, and digital line profiles. This maybe should be done several times through the pre-eruption and post-eruption plateaus, as well as for the eruption itself. Also critically, you should be making sure that some theorist full engages in trying to understand your collected data. The intermediate questions are to measure the mass flows in the system, measure the disk properties, measure the photospheric temperatures, the size of the UV emitting region, and the luminosities; all as it varies over time. The high level question is what is making the pre-eruption plateau? The ultimate question is how and why the pre-eruption plateau is related to the nova event itself.

No one had previously noticed or published the pre-eruption plateau before 1946, and no one has done more than note the rise starting around 2014-2015. (Previously, the only people who thought about the next T CrB eruption did nothing more than note that 1946-1866=80 years and apply the numerology that 1946+80=2026.) So the surity of an upcoming eruption (and its date) is new. This is providing the urge to follow the pre-eruption weird phenomena.


Spectra are gathered on http://www.astrosurf.com/aras/Aras_DataBase/Symbiotics/TCrB.htm

Thus, just continue at the best rythm as possible until the outburst. T CrB is a very rare case for which, with a good coverage, it should be posssible to get spectra of a nova just at the begining of the outburst

Spectra of the database have already been used for a publication:
https://ui.adsabs.harvard.edu/abs/2016MNRAS.462.2695I/abstract
See also:
https://ui.adsabs.harvard.edu/abs/2016NewA...47....7M/abstract
with somewhat different interpretation
and: https://ui.adsabs.harvard.edu/abs/2019AAS...23412207S/abstract

Bonne continuation!
François Teyssier
Francois Teyssier
 
Posts: 1244
Joined: Fri Sep 23, 2011 1:01 pm
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Re: T CrB near nova outburst

Postby Francois Teyssier » Sun Jun 16, 2019 11:56 pm

Update of the lines evolution from Echelle spectra:

TCrB_EWHR_Halpha.png
TCrB_EWHR_Halpha.png (10.09 KiB) Viewed 259 times

TCrB_EWHR_Hbeta.png
TCrB_EWHR_Hbeta.png (12.02 KiB) Viewed 259 times

TCrB_EWHR_HeII4686.png
TCrB_EWHR_HeII4686.png (6.91 KiB) Viewed 259 times

TCrB_EWHR_HeI5876.png
TCrB_EWHR_HeI5876.png (9.66 KiB) Viewed 259 times


I'm working on the singlet line HeI 6678, harder due to the shape of the continuum.

Since the high state detected in 2015 (Munari & al.), the general shape of recombination lines is decline, while forbidden lines increase.
At a first glance, there's no clear correlation between the oscillations clearly visible in the Balmer lines EW and the orbital period (to be confirmed)


François
Francois Teyssier
 
Posts: 1244
Joined: Fri Sep 23, 2011 1:01 pm
Location: Rouen


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