Forum der Vereinigung der Sternfreunde

There has been a discontinuity in the Deneb RV trend behaviour since 20140720 compared with the previous 38 days. (it currently appears to be an ~180 deg phase shift) See attached graph

Robin

Hi Robin,

This is fantastic! When I did my in-depth H-alpha/photometry/RV study, we were never able to stay on the target so well with time, and it looks like you are catching the changing pulsations in the act - this is what theorists are very confused about at this point. Well done!

Cheers,

Noel

Hi Robin, very spectacular! Are the data exclusively from you or are there spectra also from other observers involved? Where are all data collected?

Cheers, Thomas

Hello,
I am not sure whether my remark is really helpful but I will not keep it back. I observed Deneb recently in the NIR spectral range. The picture shows spectra from July 1st and july 3rd. At this time I was still in the experimental phase concerning NIR so I cannot garantee that the graphic shows no artefacts. Please note that the deviation concerns only the P14 hydrogen line. Later observations are more like the white spectrum from july 1st. I intend to continue observing Deneb so there might be a chance to see such differences again.
I hope this might be helpful for you.
Cheers
Christian

Hi Noel,

Note I am only following the Si II wavelength for RV measurements, not H
alpha as I need to keep the spectrograph stable on one wavelengthto get this
precision. I hope others are getting H alpha

Thomas - yes all my measurements here at Three Hills Observatory using a
LHIRES III. (It is not normally stable enough for this sort of precision
but I have a lamp in front of the telescope to superimpose calibration lines
directly on the spectrum) I do not really have this number of clear nights
but I can take spectra of such a bright target even through thin cloud for
these RV measurements and it only takes a few minutes.

Cheers
Robin

Hello Robin,

my congratulations for this precise measurements. I think that are the most precise RV-measurements made by a Lhires III I have ever seen

_________________
Herzliche Grüße / best regards

Lothar

https://lotharschanne.wordpress.com/

Hi Robin,

Congratulations for your impressive measurements.

I want to point out, however, that this behaviour of alpha Cygni (and other early-type supergiants) is well known and has been studied in much detail for almost a century now. See e.g. the detailed studies by Paddock or Kaufer et al.

http://ads.ari.uni-heidelberg.de/abs/19 ... ..17...99P

http://ads.ari.uni-heidelberg.de/abs/19 ... .320..273K

The behaviour can be described as quasi-periodic or multi-periodic, but in my opinion, the problem is not really solved. Observationally, this is a challenging problem, because many different timescales are involved. You need *very* long *uninterupted* sequences of measurements to make real progress. There are several bright prototype stars (e.e. alpha Cygni), so this in principle a problem suitable for amateurs. The requirement on the radial velocity precision are a challenge, however, as well as the dense and long time coverage.

Best regards,
Otmar