VV Cep evolution at low resolution

VV Cep 2017-2019 Campaign
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Re: VV Cep evolution at low resolution

Postby HughAllen » Wed Feb 14, 2018 8:58 pm

Hi Ernst,
I really appreciate your feedback. It is fascinating to see the comparison with the high resolution campaign results, there seems to be a reasonable correspondence. The integration interval that I use is determined by the points at which the Hα obviously emerges from the underlying continuum, so the width of the interval can vary slightly from spectrum to spectrum. So for example the width of the interval on my last spectrum captured on 11th Feb was 6554 - 6576Å, on some other spectra it has been maybe 1 or 2Å wider. Regarding the accuracy, I have been wondering for a while how to estimate the error bar I should asscoiate with the values in the graph. Would you have any advice on how to estimate that when the true value may be varying naturally from night to night?
Cheers
Hugh
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Re: VV Cep evolution at low resolution

Postby Ernst Pollmann » Fri Feb 16, 2018 3:55 pm

Hugh,
at least I would try to take spectra for several hours in order to determine the EW within the same wavelenght interval.
Over time, you can clearly see if the "intrinsic" EW has actually changed drastically. However, it should be remembered that the V-magnitude of the continuum may change during this time. At least I would try.

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Re: VV Cep evolution at low resolution

Postby Thilo Bauer » Thu Apr 26, 2018 11:06 am

Hi Hugh,

just read over the latest posts then saw your plots of EW in H-alpha and H-beta.

Could you share your results in a table format? I will try to add mine into yours and post it back. I also collected certain observations before the eclipse. Unfortunately my current observations are not that dense during eclipse due to bad weather and strong business tasks (preventing me from collecting new spectra since August 2017). I now have one new spectrum to share with you from April, 21st 2018 taken during a very nice spectroscopy workshop, that Ernst held here in Wuppertal.

It will also be interesting to have the flux values of both lines in H-alpha and H-beta. I want to do some computations with it to see if we may extract astrophysical parameters from exited gas (before that I have to refresh my knowledge about the exited interstellar gas).

Best regards,

Thilo
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Re: VV Cep evolution at low resolution

Postby HughAllen » Fri Apr 27, 2018 6:08 pm

Hi Thilo,
Would you be able to let me have the fits file of your 21st April spectrum? The Equivalent Width measurement method would then be consistent with the way I have measured the earlier spectra in my graph. I will then add that measurement to a table of all of my measurements and send that back to you. Would that be ok?
Cheers
Hugh
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Re: VV Cep evolution at low resolution

Postby HughAllen » Sat May 26, 2018 10:42 am

A remarkable spell of warm, clear weather here in Southwest England has allowed me to re-start VV Cep observations, just at the time when it is starting to climb well above the north east horizon during darkness. Now in deepest eclipse it's clear that the Hα emission is not going to fall to zero, and that the periodic variation in intensity of the emission also continues during the eclipse. I would estimate the error in the EW measurements to be of the order 5-10%
Cheers
Hugh

VVCep_EWevolution_20180525.png
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Re: VV Cep evolution at low resolution

Postby HughAllen » Sat Nov 03, 2018 6:45 pm

Latest update of the progress of the VV Cep eclipse using observations by Jim Ferrera, James Foster and myself. The latest observation by James on 28th October has shown a remarkable fall in the Hα emission...

[attachment=0]
Attachments
VVCep eclipse progress to 28th Oct 2018.png
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Re: VV Cep evolution at low resolution

Postby Ernst Pollmann » Sat Nov 03, 2018 9:49 pm

Hi Hugh,

it is interesting to see that the low-resolution monitoring shows essentially the same progress as in the high-resolution monitoring, though not as detailed. It calms me to see that paticularly the behavior around the end of october to the beginning of November has been observed in both monitorings.
vvcep_Halpha.png
vvcep_Halpha.png (21.47 KiB) Viewed 1368 times

When I saw the small EW-decrease for a first time in my monitoring, I thought that would be an error in measurements.

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The Be star is re-emerging

Postby HughAllen » Sat Jan 05, 2019 10:56 am

At low resolution the ending of the eclipse is now very apparent, which is consistent with the latest results from the high res campaign recently posted by Ernst Pollmann...

VVCep eclipse progress to 3rd Jan 2019.png
VVCep spectrum 3rd Jan 2019.png
VVCep spectrum 3rd Jan 2019.png (46.25 KiB) Viewed 859 times



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Re: VV Cep evolution at low resolution

Postby Ernst Pollmann » Sat Jan 05, 2019 3:05 pm

Hi Hugh,
very pleasant this accordance. It documents the power of low resolution spectra.
I want something add to my last posting: the attempt to calculate the diameter of the disk-like emission source (see the attached Fig.)
Eclipsing times.png
Eclipsing times.png (87.03 KiB) Viewed 856 times


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Re: VV Cep evolution at low resolution

Postby Peter Somogyi » Sun Jan 06, 2019 11:40 am

Very good, Hugh!
I also detected a small H8 (= H-zeta) flux comeup on 2018.dec.31 - compared to a 2 months previous material (2018 Nov-Dec: I had a usual outage due to bad weather).
In the 3720-4000A region, last year everything was unchanged from May till October, except the absolute fluxes varied that I'm still evaluating.

Conclusion is, H-beta seems to be in good sync with the higher Balmer lines, and it's the most direct metric for eclipse timing determination.
I wish a good continuation!
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