Observation state of the campaign

[Ernst Pollmann]

Dear colleagues,
during the coming two years I will inform you regulary to the observation state of the VV Cep eclipsing campaign.
The information includes the following main aspects: the long-term monitoring of the Halpha equivalent width (EW) and the long-term monitoring of the ratio V/R. Additionaly it includes the individual time series of the V and R component of Halpha as EW and as peak height.
Please have a look to:
http://astrospectroscopy.de/media/files/vvcep-overview.pdf

Ernst

[Ernst Pollmann]

Dear colleagues,
it seems that the eclipse has begun.

vvcep-eclipse.png (89.02 KiB) Viewed 9260 times

Any comments?

Ernst Pollmann

[Thilo Bauer]

Hi Ernst,

Just one question: Who is the lucky observer having had constantly good weather during the last 30 days?

Seriously, hard to tell. I found the data shown here starts at 15. July 2017 until today (see my last comment on this).

I assume, it is expected, that according to our discussion, the blue part of the wings should disappear first? Not quite sure without having seen the rest of the data points within a reasonable time frame before. It could be an effect of short time scale variation, or not.

During the occultation we should be able to estimate the size of the "disk", if there is a relatively sharp boundary, isn't it? Perhaps this is not the case and we have to consider some intensity variation. It could look like the expected integral intensity variation, if you think of an intensity plot of the projection of a planetary nebula, like M57 (without or with a hole, we will see).

On the other hand, and thinking of the mass transfer, this is not only disk, but also the big "tail" of mass from the supergiant to the companion. Not sure, what we should expect to see here on this very short time scale.

One other remark: I find it hard to transform the filenames of my spectra to Julian date quickly enough in my head. So I have to find a tool to translate. If we want to compare our results quickly, we should align on the preferred date format presented with our data. Either "natural" calendar dates, as Hugh presented his spectra based on file names, UTC or Julian calendar date. For a final presentation Julian dates or UTC might be reasonable decisions, however. For quick comparison, UTC should be more convenient, as this is easily done set up in my camera and observation log and usually quickly seen by inspection of the FITS files, which also use UTC datetime formats per convention instead of Julian date.

I appreciate your recommendation on this.

Thilo

[Ernst Pollmann]

Hi Thilo,
the diagram above is an enlargement the entire base line monitoring (the attached Fig.) of the group.

V & R Baseline.png (99.78 KiB) Viewed 9211 times

It should show more in detail the EW & PH behavoir during the last few days. Hope this helps for your understanding.
The left-hand side (= blue component) of the accretion disk of the B-star (which will be obscured first by the semitransparent atmosphere of the M-super giant in the line of sight) already shows a recognizable descent at JD 2457967, both in peak height and in EW.
On the other hand, the right-hand side of the accretion disk (= red component) shows a time-delayed start of coverage at JD 2457976 (also in peak height and EW).
However, it would be to early, to make statements about the size of the disk with this (vague) temporal difference and the system radial velocity.

Ernst

[marcoastro+]

Dear colleagues,

Indeed, the remark on the "lucky weather" of Thilo is interesting.
In our region it is so far the worst "cloudy" night summer in the past 10 years.

Concerning the observation state of the campaign: Ernst mentioned a turning point can be expected.
However as nicely explained by Phil Bennett the H-alpha measurements are the sum of two contributions: the smaller "accretion" disk around the B star and the more exhaustive zone of the generated H II region, which stays during totality.
Important for the spectral behaviour here is the influence of the compactness of the H II region. If its density changes when passing in front of the spectroscopic line of sight, this can influence the recordings. All depends on the behaviour of high or low density clumps, which can also be remnants of earlier mass transfer or compressed zones by winds or magnetic fields. This also influences the "steepness" of the decreasing peak heights and represent a more impressive impact on the EW values. Therefore it is not so easy to detect the exact start of the real eclipse i.e. the disappearance of the accretion disk. Even during totality a varying spectral behaviour can be measured.

KInd regards,
Marc.

[Thilo Bauer]

Hi Ernst,

However, it would be to early, to make statements about the size of the disk with this (vague) temporal difference and the system radial velocity.

I agree. So far, the EW looks more likely correlated with each other, than anti-correlated. I would expect to find most difference in intensities of the two RV "wings".

Marc pointed out a more exhaustive region of hydrogen. This is something I also would expect. It will be interesting to see, if there will remain a blue and red component of the emission in the line of sight during total eclipse. This is something we also observe with planetary nebula or bubble like H-II shells or shockwaves of stellar winds: doubled line profiles from the surfaces of the gas shells. This is indicating two "planes" of a "bubble" with opposite direction of the radial velocities of the surface along the line of sight. This is not caused by the rotation of the disk, but should show a different profile (probably more sharp). I'm curious what we will find during total eclipse.

It will be nice to study changes of the line profile instead of presenting an integrated value, like EW or intensity.

Best regards,

Thilo

[Carl Sawicki]

Hello Thilo and Marc,

You both seem to be curious about who is sending up all the VV Cep spectra ... it is possible that it is me. In the last two weeks I sent Ernst Pollmann at least ten VV Cep spectra: 07-31, 08-01, 08-03, 08-04, 08-05, 08-07, 08-09, 08-10, 08-11, 08-12. Lucky for me, we've had rain the last three days, so I'm getting a rest. Hopefully Ernst and others are filling in the needed spectra for the monitoring.

And as far as the weather, my observatory is in far west Texas, at a little over 1500 m. The weather out here is generally dry, especially during all the winter months. Spring and summer can go either way and right now we're in a 'quasi-monsoon' season, so strong thunderstorms and heavy rain can come any time. But for the most part, I'm able to get out in the observatory either side of 150 nights a year. This area in west Texas has very dark skies and the small town of Alpine (< 6,000 pop.) has very strict lighting controls (due to our close proximity to McDonald Observatory) and all the lights are yellow, and are pointed down toward the ground, so this gives me very good conditions for spectroscopy.

Wishing you clear skies,
Carl Sawicki
Alpha Observatory
Alpine, Texas

[Robin Leadbeater]

Hi Carl,

Welcome to the ARAS forum ! Can I suggest a short post in the Introductions section to let people know you are around? Mine is here for example
viewtopic.php?f=11&t=25

Cheers
Robin

[Ernst Pollmann]

Dear colleagues,
the observation state of the VV Cep eclipsing campaign has been up dated:
http://astrospectroscopy.de/media/files/vvcep-overview.pdf

Ernst Pollmann

[marcoastro+]

Many thanks Carl,

Great observing location you have there in the neighbourhood of the Mc Donalds Observatory !!
An excellent place to monitor the upcoming eclipse of VV Cep.
If you have time can you send me your spectrum of August 7th?

Keep up the excellent work!,
Kind regards,
Marc.