Observation state of the campaign

VV Cep 2017-2019 Campaign
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Re: Observation state of the campaign

Postby Ernst Pollmann » Thu Aug 02, 2018 7:26 am

… I think that this additional spectrum (total eclipse) is even more convincing.
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Ernst
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Re: Observation state of the campaign

Postby Peter Somogyi » Thu Aug 02, 2018 5:27 pm

Ernst,

I think these are the profiles I am seeing in the UV now (= tiny single emissions), and multiple observations from the past really validating the old EWs.
This all suggests then that the extended H-alpha region - with a geometry having relevant RVs positive and negative - is partially eclipsing now, whilst the star's nearby region (higher Balmer) is in a total eclipse.
The tiny stable emissions must be nebular.

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Re: Observation state of the campaign

Postby Andrew Smith » Sat Aug 04, 2018 1:44 pm

Andrew Smith wrote: ... 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...
Regards Andrew

I came across this paper https://arxiv.org/pdf/1102.5198.pdf that speculated

" However there is a visible excess of radiation near and during the eclipse (Figure 3–right panel), which could be produced by a scattering of radiation emitted by the hot component in the very extended envelope of the supergiant"

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Re: Observation state of the campaign

Postby Ernst Pollmann » Sat Aug 04, 2018 4:59 pm

Hi Andrew,
I assume, you are thinking about the small EW increase after the 1997/98 eclipse, right?
If so, then my interpretation would be another than yours:
I am still convinced that the 43 day period, which manifests in the EW variability of our current campaign, results from a precession movement of a disk-like emission region around the B star.
But the observation frequency has to be dens enough, in order to evidence them. This was the case after the 1997/98 eclipse only for a short observation period. Within this short period one could recognize a weak cyclic variability, which we observe today very clear.

With other words: an EW and an antisynchronously V/R periodicity was always present in the past 20 years. But probably with a significant distinguish: the mass and the size of the emission region around the B star was much larger than nowadays. I personaly suppose that also the precession period was at that time corresponding much larger.
And we don´t have to forget that the Halpha emission results from recombination of hydrogen atoms, which arises in the ionized gas around or near the B star. That process might be generated in the bow-shock front, in front of the emission region, which moves with supersonic velocity on the orbit of the B star through the M star wind.

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Re: Observation state of the campaign

Postby Robin Leadbeater » Sat Aug 04, 2018 5:49 pm

Andrew Smith wrote:I came across this paper https://arxiv.org/pdf/1102.5198.pdf that speculated

" However there is a visible excess of radiation near and during the eclipse (Figure 3–right panel), which could be produced by a scattering of radiation emitted by the hot component in the very extended envelope of the supergiant"

Regards Andrew


An interesting idea. It would like the recent lunar eclipse. For an observer on the moon, the sun was certainly totally eclipsed but they still see light from the sun scattered through the earth's atmosphere. Could the scattering be wavelength dependent explaining why we still see some H alpha but not the shorter wavelengths ?

Robin
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Re: Observation state of the campaign

Postby Peter Somogyi » Sat Aug 04, 2018 6:37 pm

Just stepping in with an antiproof for reflecting dust: today, the whole profile in the B star's max region (3800-4000A) is mostly matching with the profile of Alf Ori (whilst B was there, it was 4x bigger than the M component).

In other words: as of today, the B component's light ratio is close to zero - till some continuum subraction errors. The drop is more than 95% (might be 100% but I have some errors). The drop of H-alpha is order of magnitudes less.

Something I can imagine, that the more opaque red portion with H-alpha is glowing through the M layers anyhow. This way Robin's idea might work.

For this, a weaker antiproof is the H-alpha profile shape change (= the high RVs completely disappeared, lower RVs remained and lowered). Which means, high RVs (should ne B star's neightbourhood) would need to remain today then. But the high H-alpha RVs clearly disappeared, not only decreased.
Be aware H-alpha's central region after M substraction is pyramid, or the outer nebula taking out some of its central absorption. Telling just not to think it's similar to a gaussian double peak common with Be shell stars (the middle absorption is more like a direct cut). Of course, Ernst has much more experience here.

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Re: Observation state of the campaign

Postby Andrew Smith » Sat Aug 04, 2018 6:42 pm

Ernst, I was motivated by the discussion just prior to the Fig 2 in the paper you linked to. I was just speculating that rather than an extended region emitting H alpha if you were seeing the hot emitting region from the B stars potential well scattered into the line of sight while in eclipse. As Robin mentions as in a lunar eclipse.

I am no expert on this system (or any other) but as it occurred to me as a possible alternative I thought I would mention it.

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Re: Observation state of the campaign

Postby Ernst Pollmann » Sun Aug 05, 2018 7:52 am

Andrew, Peter,
as Phil Bennett already said (and I repeat my statement too): we have to consider that the emission region (disk or not disk that´s the question) is probably caused by a bow shock front due to the supersonic velocity of the B star on its orbit through the M star wind.
It seems that this "emission region" is today essential smaller than 1997/98.
This fact of observation does lead to a further "core question": what are the reasons for that?
What, if the inclination angel of the rotational axis of the B star (and hence the rotational axis of the emission region) related to the orbit has changed?

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Re: Observation state of the campaign

Postby Robin Leadbeater » Sun Aug 05, 2018 11:06 am

Hi Ernst,

I suggest we keep an open mind on the possible explanations. It is not that long ago that you rejected suggestions that there may be a contribution to H alpha emission other than the disc.

viewtopic.php?f=19&t=1798&start=60#p9322
viewtopic.php?f=19&t=1798&start=70#p9511

Robin
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Re: Observation state of the campaign

Postby Ernst Pollmann » Sun Aug 05, 2018 11:29 am

… thanks for the tip.
But, don´t worry, it is not unusual in scientific analysis that thesis from time to time (depending on updated level of knowledge) changes.

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