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| Deneb RV - discontinuity observed at 20140720 https://forum.vdsastro.de/viewtopic.php?t=4196 |
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| Autor: | Robin Leadbeater [ 23. Juli 2014, 03:08:26 AM ] | ||
| Betreff des Beitrags: | Deneb RV - discontinuity observed at 20140720 | ||
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
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| Autor: | Noel Richardson [ 23. Juli 2014, 03:53:38 AM ] |
| Betreff des Beitrags: | Re: Deneb RV - discontinuity observed at 20140720 |
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 |
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| Autor: | Thomas Eversberg [ 23. Juli 2014, 08:06:09 AM ] |
| Betreff des Beitrags: | Re: Deneb RV - discontinuity observed at 20140720 |
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 |
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| Autor: | Christian Netzel [ 23. Juli 2014, 08:43:56 AM ] | ||
| Betreff des Beitrags: | Re: Deneb RV - discontinuity observed at 20140720 | ||
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
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| Autor: | Robin Leadbeater [ 23. Juli 2014, 13:32:02 PM ] |
| Betreff des Beitrags: | Re: Re: Deneb RV - discontinuity observed at 20140720 |
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 |
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| Autor: | Lothar Schanne [ 25. Juli 2014, 13:05:57 PM ] |
| Betreff des Beitrags: | Re: Deneb RV - discontinuity observed at 20140720 |
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 
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| Autor: | Otmar Stahl [ 25. Juli 2014, 13:43:11 PM ] |
| Betreff des Beitrags: | Re: Deneb RV - discontinuity observed at 20140720 |
Zitat: 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
Hi Robin,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 |
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