Related papers: Abrupt Periodic Pulsation Resumptions in Deneb

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…

Deneb, the prototype alpha Cygni variable, is a blue-white supergiant that shows irregular variability with quasi-period around 12 days in brightness and radial velocity. Abt et al. (2023) found that larger amplitude 12-day variations…

Deneb is often considered the prototypical A-type supergiant, and is one of the visually most luminous stars in the Galaxy. A-type supergiants are potential extragalactic distance indicators, but the variability of these stars needs to be…

We write to report the discovery that Deneb is a large amplitude polarization variable. Over a ~400 d time span from August 2022 Deneb's polarization was typically around 3900 parts-per-million (ppm) in the SDSS g'-band. Yet, it varied by…

The Alpha Cygni (ACYG) variables are blue-white supergiants which display low-amplitude brightness variations of around 0.1 magnitude. The prototype Deneb shows quasi-periodic variations of around 12 days, interrupted by intervals of…

We present the results of our $UBV$ and $JHKLM$-photometry for the semiregular pulsating variable V1027~Cyg, a supergiant with an infrared excess, over the period from 1991 to 2015. Our search for a periodicity in the $UBV$ brightness…

The RApid Temporal Survey (RATS) is a survey to detect objects whose optical intensity varies on timescales of less than ~70 min. In our pilot dataset taken with the INT and the Wide Field Camera in Nov 2003 we discovered nearly 50 new…

We present fast timing photometric observations of the intermediate polar V2069 Cygni (RX J2123.7+4217) using the Optical Timing Analyzer (OPTIMA) at the 1.3 m telescope of Skinakas Observatory. The optical (450-950 nm) light curve of V2069…

(abridged) In the frame of the search for extrasolar planets and brown dwarfs around early-type main-sequence stars, we present the results obtained on the early F-type star Theta Cygni. Elodie and Sophie at OHP were used to obtain the…

There are currently two optical interferometry recombiners that can provide spectral resolutions better than 10000, AMBER/VLTI operating in the H-K bands, and VEGA/CHARA, recently commissioned, operating in the visible. These instruments…

We present results from high speed photometry of a further thirteen faint cataclysmic variables. V356 Aql (Nova Aql 1936) shows flare-like outbursts with recurrence time scales ~ 3000 s, but no coherent periodicities. Aqr1 is an…

This investigation integrates five decades of ground-based photometric data from the AAVSO, AFOEV, ASAS, ASAS-SN, and SuperWASP surveys with recently acquired TESS observations, conducting a multi-wavelength and multi-phase photometric…

AU Pegasi is a pulsating star in a spectroscopic binary system with an orbital period of 53.26 days. Between 1960 and 1990 an extremely rapid period increase was observed in the value of the pulsation period, but in the last 15 years the…

Blue supergiant stars are known to display photometric and spectroscopic variability that is suggested to be linked to stellar pulsations. Pulsational activity in massive stars strongly depends on the star's evolutionary stage and is…

Pulsations of RV Tauri-type variable stars can be governed by chaotic dynamics. However, observational evidence for this happening is usually hard to come by. Here we use the continuous, 4-year-long observations of the Kepler space…

BA-type supergiants are amongst the most optically-bright stars. They are observable in extragalactic environments, hence potential accurate distance indicators. Emission activity in the Halpha line of the BA supergiants Rigel (B8Ia) and…

Spectroscopic and photometric variability is widespread among O-type supergiants. It is linked to various phenomena affecting the star and its circumstellar environment, thereby providing direct information concerning them. To investigate…

We have used AAVSO visual and photoelectric V data, and the AAVSO time-series package VSTAR and the Lomb-Scargle time-series algorithm to determine improved pulsation periods, "long secondary periods" (LSPs). and their amplitudes in 51…

The subdwarf B (sdB) star V391 Peg oscillates in short-period p modes and long-period g modes, making it one of the three known hybrids among sdBs. As a by-product of the effort to measure secular period changes in the p modes due to…

Rigel (beta Ori, B8 Ia) is a nearby blue supergiant displaying alpha Cyg type variability, and is one of the nearest type-II supernova progenitors. As such it is an excellent test bed to study the internal structure of pre core-collapse…