Deneb, the prototype Alpha Cygni variable, is a bright A2 Ia supergiant which shows irregular variability with a 12-day quasi-period, presumed to be caused by pulsations. At the 2023 AAVSO Annual Meeting we discussed radial velocity and photometry data from several sources showing that the 12-day variations begin abruptly at an arbitrary phase, damp out after several cycles, and resume at intervals of around 75 days. Additional data with more frequent time sampling and longer time series were needed to verify the existence and precision of the 75-day interval. We have identified additional data sets and have intensified ground-based observing programs. Here we present analysis of 1) an 8.6-year photometric data set from the Solar Mass Ejection Imager; 2) BRITE Constellation light curves from six observing seasons of 60 to 180 days each, 2014-2021; 3) 4.6 years of radial velocity data from Morrison; 4) 1.4 years of radial velocity data from Eaton; and 5) additional V-band photometry from the AAVSO Photoelectric Photometry (PEP) section. Examining the SMEI data set, we find a most common 100 to 125 day interval between pulsation' resumptions. These resumptions sometimes skip intervals. We also find sudden large excursions in brightness and radial velocity which are distinct from the pulsation’ resumptions and may or may not be data artifacts. We point out changes in the average level of Deneb’s radial velocity which appear to be real given the accuracy of the measurements but are not explained.
A very interesting paper! Clearly, much about Deneb remains puzzling but these results are certainly a step forward.
Hi Horace, Thanks for commenting on our paper! The AAVSO PEP section has been devoting a lot of time to observing Deneb and other alpha Cyg variables. Tom Calderwood has been coordinating observing campaigns on a few of the brightest ACYG variables such as Deneb. We know so little about the (probably multiple) causes of their variability. To follow these quasi-periodic or aperiodic light curves we need high precision photometry for many months or years, and ideally at least one data point per night. Joyce
If they are of any interest, I have a series of RV measurements of Deneb to 1 km/s 2 sigma precision covering 6 months from June-Dec 2014. They can be seen plotted in this video presentation at 20:10
https://britastro.org/videos/pushing-the-limits-using-commercial-spectrographs-2
Cheers
Robin
Hi Robin,
Thank you so much for sending the link to your video with this data! Yes, they are of high interest! The precision you are able to get is impressive! I think that Nancy Morrison (AAVSO and JAAVSO editor) will be interested as well. The time frame of your data overlaps with some of the BRITE constellation photometry data on Deneb, so I am interested to plot these on the same curve and look for correlation. Would you be able to send the time series to me? I can also include you as a co-author on any update talks or new publications. Joyce