Abrupt Pulsation Resumptions in Deneb: An Update

• DOI: 10.48550/arxiv.2503.20058
• Publication Date: 2025-03-25
• Authors: Joyce Ann Guzik; Brian Kloppenborg; Noel D. Richardson; Jason Jackiewicz; N. D. Morrison; Tom Calderwood; A. Pigulski

Deneb, the prototype Alpha Cygni variable, is a bright A2 Ia supergiant which shows irregular variability with 12-day quasi-period, presumed to be caused by pulsations. At 2023 AAVSO Annual Meeting we discussed radial velocity and photometry data from several sources showing that variations begin abruptly at an arbitrary phase, damp out after cycles, resume intervals of around 75 days. Additional more frequent time sampling longer series were needed verify existence precision 75-day interval. We have identified additional sets intensified ground-based observing programs. Here present analysis 1) 8.6-year photometric set Solar Mass Ejection Imager; 2) BRITE Constellation light curves six seasons 60 180 days each, 2014-2021; 3) 4.6 years Morrison; 4) 1.4 Eaton; 5) V-band Photoelectric Photometry (PEP) section. Examining SMEI set, find most common 100 125 day interval between `pulsation' resumptions. These resumptions sometimes skip intervals. also sudden large excursions in brightness are distinct may or not artifacts. point changes average level Deneb's appear real given accuracy measurements but explained.