The HeI6678 line in P Cyg

The HeI6678 line in P Cyg

Postby Ernst Pollmann » Tue Sep 27, 2011 7:08 am

Beside of the primary aim of the P Cyg campaign, I studied the behavior of the HeI6678 line, which represents the helium-forming zone (12-13 stellar radii; O. Chesneau et al., ASP Conf. Ser., 233, 2001), near the central star (see attached pdf file).

A series of 76 HeI6678 spectra, obtained during April 2003 until today, shows fig.1. It shows clear the variations in the emission intensity, variations of the central absorption core and its movement in wavelength. The correlation of the emission intensity and the central absorption core is obvious (fig.2). This is due of variability of optical depth, as result of a variability in mass-loss.

Two spectra (JD 2455767 & 2455675) in fig. 3 shows the measured maximum difference so far in expansion velocity of approx. 40 km/s. This is qualitatively in good agreement with Markova 1993 (A&A, 273, 555).

From JD 2555444 until now the central absorption core is variable in a quasi-periodic way (fig. 4). A period analysis of this time section (fig. 5 & 6) reveals a period of 158 d.

As far as I know, is this the first time, that the central absorption core of HeI6678 in P Cyg does show this sort of quasi-periodic variability.

Ernst Pollmann
-------------------------------------------------
Active Spectroscopy in Astronomy
http://www.astrospectroscopy.de

HeI6678_1.jpg
HeI6678_1.jpg (67.21 KiB) Viewed 3932 times



HeI6678_2.jpg
HeI6678_2.jpg (43.89 KiB) Viewed 3932 times
Last edited by Ernst Pollmann on Wed Sep 28, 2011 6:51 am, edited 1 time in total.
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Re: The HeI6678 line in P Cyg

Postby Olivier Thizy » Tue Sep 27, 2011 8:28 am

Ernst,

Excellent result.

I had trouble to view the image but right-clicking on them and selecting "display image" allowed me to see the very nice periodic graphs.

I would be interested to understand what phenomenon is creating this behaviour. Are those k-mechanisms similar to what is seen on BW Vul or beta Cep for exemple?

Cordialement,
Olivier Thizy
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Re: The HeI6678 line in P Cyg

Postby Ernst Pollmann » Tue Sep 27, 2011 1:10 pm

Olivier,
this is not easy explain, but it seems, that the variations in the intensity of the emission component not to be correlated with the velocity variations of the absorption core with maximum intensity (ACMI) (Stahl et al.; 1991, Astron. Ges., Abstr. Ser. 6, 71).
The velocity of the ACMI does correspond with the optical depth and is variably with time (time scale 100-200d).
The ACMI is formed in an extended region with velocity gradient. The observed velocity variations may be simply explained by variations in the opacity of this region, and the variability in intensity of the ACMI is probably a result of quasi-periodic variations in the rate of mass-loss.

Ernst
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Re: The HeI6678 line in P Cyg

Postby Ernst Pollmann » Mon Nov 09, 2015 6:52 pm

Dear colleagues,
here is an up-dated report of the monitoring of the HeI6678 absorption line of P Cyg:

http://astrospectroscopy.de/media/files/pcyg_He6678.pdf

Ernst Pollmann
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Re: The HeI6678 line in P Cyg

Postby Ernst Pollmann » Tue Aug 08, 2017 6:54 pm

Dear colleagues,
here is an up-dated report of the monitoring of the HeI6678 absorption line of P Cyg:

http://astrospectroscopy.de/media/files/He6678_Aug_2017.pdf

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