P_Cyg samedi soir comparaison

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Dubreuil Pierre
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P_Cyg samedi soir comparaison

Post by Dubreuil Pierre »

Bonsoir à tous

Samedi soir les Nice People ont frappé à Calern ! :mrgreen:

Alain avec son C11 et moi avec mon C8 (lHiresIII 2400) nous avons imagé entres autres P_Cyg à 2 heures d'intervalle.
Il y a une différence de "flux" en nos 2 spectres. Peut on estimer que c'est dû à une variation de cette étoile ou une différence de traitement ?

Cordialement

Pierre
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comparaison P_Cyg à 2 heures d'intervalle  avec C8 et C11
comparaison P_Cyg à 2 heures d'intervalle avec C8 et C11
_p-cyg_20111001_943_pierre-Alain.png (6.4 KiB) Viewed 11973 times
Thierry Garrel
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Re: P_Cyg samedi soir comparaison

Post by Thierry Garrel »

super observation. Ca m'a l'air réel.
Vos continuum s'ajustent bien, l'absorption du profil P cyg aussi, il n'y pas de différence de résolution. L'intensité H alpha qui varie en 2h c'est tout à fait ce que Ernst essaye de montrer.
Vous devriez lui soumettre ces deux spectres.
Vous aviez mis vos cagoules ? :shock:
lopez alain
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Re: P_Cyg samedi soir comparaison

Post by lopez alain »

Bonjour

Oui effectivement il y a une variation en flux très importante de P Cygni, j'ai repris le spectre que j'avais pris le 4 aout à l'OHP et le dernier pendant la soirée à Calern avec Pierre (sans les cagoules) il faisant un temps magnifique.
Celui de samedi 1 octobre monte à 26!
Les spectres sont partis chez Ernst.
Bonne journée.
A+ Alain
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p_cygni_20111001_875r.jpg
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p_cygni_20110804_928r.jpg
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Thierry Garrel
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Re: P_Cyg samedi soir comparaison

Post by Thierry Garrel »

Pour faire court, le continuum bouge en ce moment. C'est à dire la photométrie de l'étoile. C'est pas tant l'intensité absolue de l'émission h alpha qui s’accroît, mais c'est l'intensité relative au continuum qui varie car lui s'affaiblit, la mag V plonge ces derniers temps. Une anticorrélation entre mag V et largeur équivalente de la raie a bien était mise en évidence. Ce qui est assez judicieux c'est de surveiller d'autre domaine, par exemple HeI6678, pour vérifier cette relation. Voir les post de Ernst à ce sujet.
En plus des fluctuation trés rapides sont suspectées, c'est peut être ce que vous avez attrapé. Donc excellente idée.

C'est dommage pour les cagoules vous étiez si beau avec ;) Image
Ernst Pollmann
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Re: P_Cyg samedi soir comparaison

Post by Ernst Pollmann »

... Pierre and Alain sent me their spectra for EW evaluation.

Here the results:
Pierre (observation at 22:38:02): EW (average EXCEL/MK32) = -91.8 A Alain (observation at 00:30:90): EW (average EXCEL/MK32) = -99.4 A

These results confirms, what we could assume meanwhile during the last weeks:
there is a shortterm variability in EW and hence in V too. It's really a large incidental occurence, that both observer just during this jerky phase did take such important spectra. And fortunately with a certain difference (approx. 2 hr) in time. Within the project consortium we discussed already somewhat about the phenomenology behind this behaviour of the star.

Observation facts:
A clear anti-correlation between Halpha EW (fig.1) and the continuum brightness (fig.2). Latter represented as photometric V measurements of the AAVSO-observer. We have to expect such a connection between Halpha EW and the underlaying continuum brightness (Vphot), because of the continuum normalisation for EW calculation. Since the beginning of the campaign (November 2008) we haven't been able, to find with this large clarity this connection, how it is observable during the last weeks. Currently we can demonstrate, what's among others behind the huge variability in EW: variations of the continuum brightness (Vphot) and the Halpha line flux itself (see below).

Questions:
The question is, what causes the variability in Vphot. Variable mass-loss in the outer photosphere of the central star ? Variability of the ionisation structure in the wind ?

To get somewhat more clarity here, we monitor within the project campaign the intrinsic Halpha line flux (fig.3; for definition of the flux see description of the Y-axis). To find out if and how the flux obtained from the spectral line profiles varies, the EW measurements is corrected for the effect of continuum variation. In practise, we correct EW with a simple division by 10(0.4*Vphot). Then the derived quantity is not the line flux in physical units, but a quantity proportional to the physical line flux, corrected for continuum variations.

The observation of the intrinsic line flux is significant, because the included intrinsic variations are due to variable mass-loss rate as variations of wind density and to changes in the ionisation structure. The Halpha line flux does show us in fig.3, there is a fairly variability during the last weeks.

A variability in mass-loss rate should be also observable in the helium forming zones, near the central star (approx. 12-13 stellar radii). That's why I monitor contemporaneously to Halpha the emission and absorption component in He6678. That's why it would be great, to get spectra of the ARAS-group, which includes this spectral region.

In order to avoid too long text, I will come back for a discussion about the He6678 line later.

Ernst Pollmann
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Active Spectroscopy in Astronomy
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pcyg.jpg
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Francois Teyssier
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P_Cyg samedi soir comparaison

Post by Francois Teyssier »

A low resolution spectrum, one day before the nice people's spectra.

Image

I measured EW = -94.5
Integration between 6518 and 6612 angströms

Also a gaussian fitting with two components :

Image

Principal component EW = -74.6 FWHM = 6.9
Broad component EW = -20.4 FWHM = 34.5
Sum = -95.0 A

The P Cygni profile on He I 5876 and 6878

Image
Image

Best regards
François Teyssier
http://www.astronomie-amateur.fr/feuill ... /PCyg.html
Ernst Pollmann
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Re: P_Cyg samedi soir comparaison

Post by Ernst Pollmann »

... the Halpha line profile is shaped:

1) by an compound radiation of recombination and ionisation of the wind (latter caused by the central star, Teff ~ 21000 K),

2) an emissivity of the non-coherent electron scattering (see Najarro, Hillier, Stahl; A&A, 326, 1117-1134), and

3) by the wind (self) absorption process in the line of sight of the observer.

Small changes in luminosity and / or mass can lead to a dramatic changes of the ionisation structure of H (and He) in the wind.

Attached you can find a plot, where these three contributions are modeled by using of a simple Gaussian distribution. The edges (wings) of the Halpha profile are essentially dominated by electron scattering (see Najarro, Hillier, Stahl; A&A, 326, 1117-1134). The high velocity dispersion of the electron scattering, leads to a wide profile expansion on the wavelength scale. Depending on its intensity, this range can reach from 6515 to 6610 Angströms.

That means, the EW evaluation of the Halpha profile should be performed at least within this wavelength range. The attached plot of my 2011-09-05 observation shows impressive this wide wavelength range of the electron-scattering contribution.

Ernst Pollmann
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Active Spectroscopy in Astronomy
http://www.astrospectroscopy.de
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fit profile pcyg.jpg
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Francois Teyssier
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Re: P_Cyg samedi soir comparaison

Post by Francois Teyssier »

Hi Ernst,
Thank you for the explanations.
The range you mention (6515 to 6610 Angströms) is almost the same I used (6518-6512).
I see that the assymetry in the broad component is in fact the contribution of CII.
Best regards
François Teyssier
Christian Buil
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Re: P_Cyg samedi soir comparaison

Post by Christian Buil »

Hi,

P Cygnii spectra comparison for date 30.885/08/2011 and 5.852/10/2011 (C11 + eShel).

Halpha region:

Image

For the two dates the Halpha peak intensity is more intense in the latest observation.
(small difference).

Details:

Image

Image

For the two date, the HeII intensity is nearly the same (perhaps inverted).

Note : the Earth helocientric velocity is corrected (ISIS tool) and telluric
lines are removed.

Now details of Na region:

Image

Image

Note the very stable aspect of the spectrum for the two date,
except Na doublet (interstellar Na is inchanged, proof of data quality):

Image

Christian Buil
Ernst Pollmann
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Re: P_Cyg samedi soir comparaison

Post by Ernst Pollmann »

Christian,
many thanks for your spectra. I evaluated Halpha EW (fig.1) and HeI6678 as well.

Because of the observed currently increase and variability of the Halpha line flux (fig.2), we have to consider what could be the reason: variation of mass-loss, or variation of the ionisation structure due to changes of luminosity and or temperature of the star.

The absorption component of HeI6678 in the line of sight of the observer should be an indicator for increase / decrease of mass-loss rate within the helium forming zones.

Fig. 3 shows since 2003 in HeI6678 the connection between F/Fc of the absorption core with max. intensity (ACMI) to F/Fc of max. emission intensity. The values of your spectra are marked with a red circle in this plot. Fig. 4 shows your both spectra (5803 & 5840) in context to the other HeI6678 observation so far.

At present we are almost in a phase of a ACMI-maximum (fig.3), what means (in my opinion), an increase of the mass-loss rate did probably happen. More ejected matter into the shell, leads to an increase of emission activities. This is exactly what we observed on the other hand in Halpha and in the max. intensity of HeI6678. I'm thinking, these observation results do complement to each other.
pcyg1.JPG
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pcyg2.JPG
pcyg2.JPG (67.58 KiB) Viewed 11879 times
Ernst Pollmann
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Active Spectroscopy in Astronomy
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