Observation state of the campaign

[Peter Somogyi]

Hello Ernst,

Unfortunately, there is no voice file attached with that pdf on shelyak, and the pdf reads like an explicit model suggestion.
And, another document http://astrospectroscopy.de/media/files/SAS_2015.pdf: Fig.9 also detailing - another kind of - disk model, like an already known fact.
I'd suggest updating these easy-to-find pdf docs putting a red warning "2018.04.07: Disk model is in question" over these pictures.

- Peter

[Ernst Pollmann]

Dear colleagues,
I want offer for discussion the following thoughts concerning the V/R variability in VV Cep:
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The investigations of Wright (1977) show that the H-alpha emission component is formed within the accretion environment of the B star, as an undisturbed, intrinsic single emission (dotted lines in the following Fig.).

Fig. 1.png (157.9 KiB) Viewed 6532 times

After Wright the entire binary system is enveloped of a cloud of neutral hydrogen, which produces in the observers line of sight, a central absorption line in the Halpha emission center. For this reason this emission appears split into two components, the V and the R components.
Because of the orbital movement of the B star around the M star (the following Fig., above, RV curve), the H-alpha emission barycenter naturally follows the radial velocity of the B star. In other words, the intrinsic single Halpha emission and its components V and R moves back and forth behind the central absorption line, which leads to a periodic change of the V and R intensities, which is exactly what we have observed in our long-term V/R monitoring (following Fig., bottom).

Fig. 2.png (89.85 KiB) Viewed 6532 times

But, the 43.7 day V/R period must have another cause. The bow-shock-front before the B star as consequence of the appox. 40 km/s supersonic movement of the star through the stellar wind of the M star, (postulated by Ph. Bennet) generates a pattern of longitudinal shock-waves in the flow of gas behind the shock-front, with corresponding periodic changes in the radial velocity.

https://de.wikibooks.org/wiki/Physik_Ob ... _Wellen_(Längswellen)

https://en.wikipedia.org/wiki/Shock_wav ... trophysics

These changes in RV are analogous to the long-term V/R changes mentioned above with the superimposed short-term period of 43.7 d in V/R. With this scenario, the phenomenon of the observed V/R variability can be explained much more reasonably than with the disk model of the past. Because Phil is informed, his comments on these considerations would be appreciated.

Ernst Pollmann

[Peter Somogyi]

Hello Ernst,

Looking at these graphs, H-alpha looks still rotational rather than coming from a bow shock: almost constant {height, width} of the approximated bell curve.
At least I would expect very different bell curves at phases {0, 0.25, 0.5, 1} (the random absorbtions appearing on top of the V peak can be ignored, that's a shortterm change I often saw in the UV end too).
But maybe you have better quality data from the recent decades to present here.

Cheers,
Peter

[Ernst Pollmann]

Dear colleagues,
after a long break here an information to the current state of our joint monitoring. How the variations of EW (plot top) and V/R (plot bottom) are to understand, we want to describe soon in a corresponding publication. Until then I ask still for some patience.

EW & VtoR.png (127.4 KiB) Viewed 6360 times

Ernst Pollmann

[Ernst Pollmann]

Dear colleagues,
thanks to the professional collaboration with the many ARAS colleagues and in particular the counseling of our professional project astronomer Phillip Bennett, a first publication of our common eclipsing campaign was completed.
This has now been accepted by IBVS and is available as a preprint under the following link:
http://astrospectroscopy.de/media/files ... .-6249.pdf

A second, continuing publication will be written after the end of the eclipsing process in which the detailed scientific interpretation of the observed phenomena is more in the foreground.

Ernst Pollmann

[jack martin]

Ernst and colleagues,

I am pleased to see this project going so well, this is due to good management and communication.

I started taking spectra on 2015-08-26 and have contributed 115 nights of observations so far.

So, Connect - Communicate - Collaborate.

Regards,

Jack

Essex UK

[Ernst Pollmann]

Dear colleagues,
here some further thoughts:

1) In our IBVS paper we wrote that Wright found that the emission centroid follows the velocity of the B star on its orbit. I have tried to confirm that with the attached Fig.(top). It shows at first on the right ordinate the calculated orbital radial velocity of the B star as blue curve.

I inserted in this diagram on the left ordinate our V/R monitoring since JD 2451413 (with T0 = JD 2438461 = time of periastron after Wright, 1977) but with - 0.15 shifted in phase. This process led to a very well accordance of both curves (subjective judged by eye). The amount of the phase shift comes from period changes since JD 2438461 (1964 March 06). This superimposed diagram might be used in order to confirm the statement of Wright.

considerations.png (139.51 KiB) Viewed 6184 times

2) The attached Fig. (bottom) shows that the Halpha EW of the current eclipse does not reached the depth of the 1997/98 eclipse. For my understanding this says that the "emission region" in the vicinity (or around ?) the B star is corresponding clearly smaller in size than during the eclipse 1997/98.
Because of this smaller size we have been able to find out the small precession period of "only" 43 days. This was not possible while the eclipse 1997/98 because of
- the use of a prism spectrograph with too low spectral resolution,
- too low observation density,
- a larger size of the "emission region (disk?)" and hence
- the (probable) corresponding much larger precession period.

Comments?

Ernst Pollmann

[Andrew Smith]

Ernst, I have just been reading the paper you linked to above. A very impressive undertaking both observationally and in the analysis.

I am no expert on Red Supergiants but I recently read Emily M Levesque book "Astrophysics of Red Supergiants" and it occurred to me that rather than an extended hot emitting region the smaller very hot region close to the B star you mention might be illuminating the dust around the M star as in a reflection nebula. With the changing aspect during the eclipse creating some of the effects seen by your team.

Probably utter nonsense.

In any case congratulation on the work.

Regards Andrew

[Peter Somogyi]

I have a few (2 x H8 + CaII region, 2 x H12 region, one night 2hrs material for each) raws since 2018-05-26, and the only remarkeable features are Balmer (H12, H11 are the most prominent). A single weak _unresolved_ emission peak per each (looks stable). I will process it when have time (no serious change since winter).
The first thought in my mind was Andrew's comment when I saw them, must be some ambient or nebular light.

But what differentiates H-alpha from the higher Balmers today in the eclipse, that it's still having relevant RVs.

Looking the earlier H-alpha eclipse much deeper, it raises the need for a deeper historical investigations (e.g. depth of earlier eclipses? wasn't just the signal below a minimal SNR? ).

- Peter

[Ernst Pollmann]

Hi Peter,
you wrote:
Looking the earlier H-alpha eclipse much deeper, it raises the need for a deeper historical investigations (e.g. depth of earlier eclipses? wasn't just the signal below a minimal SNR? ).
The attached two spectra (50326 out of eclipse and 50640 in eclipse) shows that in spite of the modest spectral resolution of the used prismen spectrograph, the Halpha emission was evaluable without any problems. The S/N with 75 to 85 was sufficient to determine the EW.

50640_50326.png (76.89 KiB) Viewed 6145 times

With other words:
there is not doubt on the depth of the 1997/98 eclipse.

Ernst