Radius Estimation of VV Cep´s disk

VV Cep 2017-2019 Campaign
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Radius Estimation of VV Cep´s disk

Postby Ernst Pollmann » Mon Apr 10, 2017 7:59 am

Dear colleagues,

I would like to ask, whether there is a certain interest in a campaign to estimate or calculate the radius of the accretion disk of VV Cep.

High resolved Halpha spectra, how they are currently received by different observers, do provide the opportunity in August this year, to perform such high interesting goal.

At the beginning of the eclipse, we could observe, the different beginning of the decrease of the intensity of the Halpha emission components V and R. Based on radial velocity measurements of the central absorption core of Halpha, one could calculate the effective radius of the accretion disk of the B companion.

The enclosed Fig. decribes the equivalent widths of the violet (filled circles) and red (opne circles) component of the Halpha emission as function of the Julian Date.
vvcep.png
vvcep.png (70.75 KiB) Viewed 1353 times


This had been done in the past by Möllenhoff & Schaifers 1978 & 1981, A&A 64, 253-258 and A&A 94, 333-337, and by Kawabata et al. 1981, Publ. Astron. Soc. Japan, 33, 177-188.

It would be great, if this interesting aspect in observation of VV Cep would get a certain attention.

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Re: Radius Estimation of VV Cep´s disk

Postby Ernst Pollmann » Tue Apr 18, 2017 2:07 pm

Dear colleagues,
enclosed you can see a plot of the time behavior of the Halpha peak height & equivalent width of the V and R component (from spectra of different observers) in order to get a first impression of the baseline of these emission components out of eclipse. The last measurement in that plot is from April 18th (J. Guarro).
At least the peak heights of both components seems to provide a good chance to determine the exact beginning of the eclipse. The dispersion of the measurements comes from the "natural" activities of mass transfer from the M2 super giant into the B star disk (EW & V/R variability).
The Halpha V&R and V/R are high variable parameters with a certain periodic behavior. Please have a look to the investigation we recently published at IBVS No. 6156:
http://astrospectroscopy.de/media/files ... 156-02.pdf

The source of the variability of Halpha, originating from an accretion region around the hot companion, remains unclear and the time sampling of these Halpha observations are too sparse to permit a meaningful period analysis. See our IBVS publication No. 6198:
http://ibvs.konkoly.hu/pub/ibvs/6101/6198.pdf

The more spectra we collect, the more precisely would be the estimation of the time differences of the V and R eclipse. Comments are welcome!
eclipse-monitoring.png
eclipse-monitoring.png (17.97 KiB) Viewed 1317 times

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Re: Radius Estimation of VV Cep´s disk

Postby Olivier GARDE » Wed Apr 19, 2017 1:25 pm

Here's a spectrum taken this morning with ESP (R=30000)
The H Alpha profil.

Image
LHIRES III #5, LISA, e-Shel, C14, RC400 Astrosib, AP1600
http://o.garde.free.fr/astro/Spectro1/Bienvenue.html
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Re: Radius Estimation of VV Cep´s disk

Postby Ernst Pollmann » Thu Jun 01, 2017 4:31 pm

Dear colleagues,
Jack Martin sent me a lot of spectra which did fill some gaps of the year 2015 and 2016 (see the attached monitoring). As we can see, the variability of the peak height of the V component becomes more and more smaller the more the moment of the eclipse is approaching.
I think that in the current phase (shortly before the eclipse and in the line of sight) the large and expanded Halpha emission-forming area (where the scattering will be produced) more and more is diving into the semi-transparent atmosphere of the M supergiant, and therefore the divergence of the peak height variability becomes smaller and smaller.
The divergence should become almost zero (ideal) and the peak height should remain stable, if the moment of the eclipse is reached.
vvcep_V&R.png
vvcep_V&R.png (19.22 KiB) Viewed 1033 times

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Re: Radius Estimation of VV Cep´s disk

Postby Ernst Pollmann » Wed Jun 14, 2017 12:44 pm

Olivier GARDE wrote:Here's a spectrum taken this morning with ESP (R=30000)
The H Alpha profil.
Image


... Olivier,
could be so friendly to send me your spectrum?

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Re: Radius Estimation of VV Cep´s disk

Postby Ernst Pollmann » Wed Jun 14, 2017 1:03 pm

Dear colleagues,
against the background of the VV Cep eclipse, starting on 4 August 2017, an observation campaign during the next OHP meeting would be very helpful. As much spectra as possible during that meeting would contribute to determine the beginning of the eclipse as precisely as possible.
The attached monitoring shows our current effort, to determine the baseline (peak height and EW) of the V and R component before the eclipse (Fig. above)
After a review of the EW evaluation of the used spectra of the different observers with a more precise normalized continuum and a precise wavelength section of both components, this parameter is now useable (Fig. bottom).
Comments are welcome!
V & R Baseline.png
V & R Baseline.png (94.48 KiB) Viewed 938 times

EW-evaluation.png
EW-evaluation.png (17.6 KiB) Viewed 938 times

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Re: Radius Estimation of VV Cep´s disk

Postby Ernst Pollmann » Tue Jun 27, 2017 8:42 am

Dear colleagues,
a revision of the analysis of the previous campaign spectra has now led to the use of the equivalent width (EW) of the red and blue components for the determination of the baseline (see attached Fig.)
vvcep.png
vvcep.png (100.27 KiB) Viewed 780 times

In view of the immediate imminent eclipse, a well-defined base line now appears for both, the peak height and the EW. At the upcoming OHP spectroscopy session in the last week of July, we will try to improve the quality of the baselines by further observations.

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Re: Radius Estimation of VV Cep´s disk

Postby Ernst Pollmann » Thu Jul 06, 2017 6:46 am

Dear colleagues,
please don´t forget to observe VV Cep.
It is not exclude that the eclipse could begin some days before the calculated date August 4th.

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Re: Radius Estimation of VV Cep´s disk

Postby jack martin » Wed Jul 19, 2017 9:19 pm

Ernst,

Yes, its possible the eclipse may occur before the calculated date, only observations can confirm that.

So, I am monitoring as and when clear nights prevail here in the UK.

Regards,

Jack

Essex UK
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