Observation state of the campaign

VV Cep 2017-2019 Campaign
Moderator for this forum: Ernst Pollmann

Re: Observation state of the campaign

Postby Ernst Pollmann » Sat Aug 19, 2017 4:46 pm

Hi Marc,
because there is no physical correlation of Vmag and Halpha emission, I wonder: causes, which are connected with emission activity of the B star?

Ernst
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Re: Observation state of the campaign

Postby marcoastro+ » Sun Aug 20, 2017 8:23 pm

Dear Ernst,

It is hardly thinkable that there are no pulsations active in this complex binary system. Could it be possible that the results of the correlation study between H-alpha EWcorr and Vmag with correlation coeff. R=0.06 represent the final result of a "filtered" or "quenched" system. It is only an idea to propose the influence of a huge H II region, which could function as an envelope around the binaries. Its varying compactness (cave line of sight and inclination measurements) could than function as a sort of "sponge" filtering or quenching the system's behavior.
I think asteroseismology could give us a way out to know which (radial or non radial) nodes are responsible.

Simultaneously we have indeed to focus on the accretion disk of the B companion ,which could have an irregular behavior. Normally we would/could expect decreasing EW values when the disk becomes less dense.

Marc.
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Re: Observation state of the campaign

Postby Ernst Pollmann » Mon Aug 21, 2017 3:22 pm

Hi Marc,
irregular pulsations seem to be typicaly for late-type super giants. In our IBVS paper (No. 6198) we described our found period of 145 days and could confirm the 150 day period (first proposed by Hayasaka 1971) which causes by irregular pulsation of the M star. Of course we could imagine some different "fitting" scenarios, but all of them would be speculation in the current situation.

Another open question could be, why also the R component during the present eclipse (it take place right now?) does show nearly the same intensity variation of the V component, and why it decreases at present, despite its formation diametrically to the other side of the accretion disk? It should remain stable and only show an intensity reduction with a time delay, when the other edge (side) of the disk is eclipsed.
vvcep-overview.png
vvcep-overview.png (123.8 KiB) Viewed 3447 times

Ernst
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Re: Observation state of the campaign

Postby marcoastro+ » Mon Aug 21, 2017 8:37 pm

Amazing, Ernst, apparently VV Cep is in transition to a kind of CE phase, which influences temporarily the V & R components.....

Marc.
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Re: Observation state of the campaign

Postby Ernst Pollmann » Fri Aug 25, 2017 4:32 pm

Dear colleagues,
the somewhat different form of the diagrams (logarithmic ordinate, longer time base) shows for V&R EW and PH from my point of view that we are already in eclipse at least since end of May this year (JD 2457900).
vvcep_V&R_EW.png

vvcep_V&R_PH.png

Comments are welcome!
Ernst
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Re: Observation state of the campaign

Postby jack martin » Fri Aug 25, 2017 5:10 pm

Ernst,

Fascinating stuff, we are gathering data for vv cep at a special time.

Its great to be part of this campaign.

Regards,

Jack

Essex UK
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Re: Observation state of the campaign

Postby marcoastro+ » Fri Aug 25, 2017 9:29 pm

Dear Ernst,

This analysis gives a remarkable turn in the project. This points towards your latest re-calculation of the beginning point of the eclipse, which I think was in the beginning of June. With this latest graphical presentation it seems to be even earlier. What is the standard deviation of the measurements in respect to the mean values of R and V (PH and EW) ? Perhaps also an R to V plot? Perhaps another refined calculation of the date?

If this trend is correct, I'm thinking of an ETV (Eclipse Timing Variation) which can be caused by:
- Mass transfer
- Third body influence (an exoplanet around the M star would be more a dream, I think, but....NSN) combined with possible apsidal motion.
- Applegate effect?

So the story of King Cepheus' treasures could become more intriguing than thought....

Kind regards,
Marc.
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Re: Observation state of the campaign

Postby Ernst Pollmann » Sat Aug 26, 2017 9:42 am

Dear Marc,
from my point of view it seems to be not easy and not meaningful too, to define average values or standard deviations, since the variability of V&R seems to be (out of eclipse) stochastically.
That´s why our out of eclipse base line is not explicit a strict straight line. It is more or less a tendency line, smoothed on the variability. And our V&R values fit very well in that tendency. Because of that I think we can speak only of a qualitative assessment than of a statistical evaluation. So the question is at all, whether a statistical statement makes sense in this certain case.
Nevertheless, there are error ranges, at least in evaluation, that´s clear. The overall accuracy of the EW and PH determination of V&R depends on:

1) the quality of the spectra taken during the observed night
2) the reduction process (spectrum processing) of the individual observers
3) the determination in the normalized spectrum.

To 1):
I am not able to estimate this order of magnitude, but my own experience says, this is approx. in the order of magnitude (+/-) 3% in EW for one single observation.

To 2):
I am also not able to estimate the accuracy of the spectrum processing of the given observer. This will remain an unknown factor (at least for me).

To 3):
Here I can speak only about the reproducibility of normalization, and about the accuracy in definition of the integration wavelength area. This reproducibility lays in the order of magnitude (+/-) 5% in EW. This is the only thing I can do when drawing the monitoring diagrams: to insert that kind of error bars in EW and PH.

OK, a V/R plot will comes in the afternoon or tomorrow. Concerning to recalculate some ephemeries we should wait what our further observations will say.

Ernst
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Re: Observation state of the campaign

Postby Ernst Pollmann » Sat Aug 26, 2017 12:36 pm

Dear colleagues,
here comes the Halpha V/R plot.
VV Cep VtoR.png

Two things confuses me:

1) It seems there are cyclic V/R variation with "periodes" (?) of approx. 40-50 days.

2) (see the both plots above from Friday).
V&R EW and PH seems to decrease simultaneously, although R (compared with V) should descent with a certain time delay, corresponding its formation diametral on the opposit side of the disk.
Any idea?

Ernst
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Re: Observation state of the campaign

Postby marcoastro+ » Sat Aug 26, 2017 4:18 pm

Many thanks, Ernst for this quick calculation of the V/R graph.

1) Short cyclic character
could be caused by an apsidal motion of the accretion disk, typified by an unequal distibution (hence, rotation) of matter in the envelope.


2) No major delay between V and R descents
This indicates that the descents of the V and R component are somewhere "locked" here in their changes.

Kind regards,
Marc.
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