Let there be more variability in two gamma Cas stars

Abstract

We investigate the short-term optical variability of two gamma Cas analogs, pi Aqr and BZ Cru, thanks to intensive ground-based spectroscopic and space-borne photometric monitorings. For both stars, low-amplitude (mmag) coherent photometric variability is detected. The associated signals display long-term amplitude variations, as in other Be stars. However, these signals appear at high frequencies, especially in pi Aqr, indicating p-modes with a high degree l, a quite unusual feature amongst Be stars. While BZ Cru presents only low-level spectral variability, without clear periodicity, this is not the case of pi Aqr. In this star, the dominant photometric frequencies, near ~12/d, are confirmed spectroscopically in separate monitorings taken during very different disk activity levels ; the spectroscopic analysis suggests a probable tesseral nature for the mode.

accepted by MNRAS - the arxiv version has some figures in low-resolution

References in corpus (19)

• The Transiting Exoplanet Survey Satellite
• The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms
• The BRITE Constellation nanosatellite mission: Testing, commissioning and operations
• A new method for the spectroscopic identification of stellar non-radial pulsation modes. II. Mode identification of the Delta Scuti star FG Virginis
• BRITE-Constellation: Data processing and photometry
• A propelling neutron star in the enigmatic Be-star $\gamma$~Cassiopeia
• MOST detects SPBe pulsations in HD 127756 & HD 217543: Asteroseismic rotation rates independent of vsini
• Three discoveries of gamma Cas analogs from dedicated XMM-Newton observations of Be stars
• Short-term variability and mass loss in Be stars II. Physical taxonomy of photometric variability observed by the Kepler spacecraft
• Stellar parameters and H$\alpha$ line profile variability of Be stars in the BeSOS survey
• TESS observations of Be stars: a new interpretation
• Discovery of Rapidly Moving Partial X-ray Absorbers within gamma Cassiopeiae
• On the X-ray and optical properties of the Be star HD 110432: a very hard-thermal X-ray emitter
• Surprises in the simultaneous X-ray and optical monitoring of pi Aqr
• Short-term variability and mass loss in Be stars V. Space photometry and ground-based spectroscopy of $\gamma$ Cas
• Ultraviolet Activity as indicator of Small-scale Magnetic Fields in gamma Cassiopeiae
• Variations of the HeII 1640A Line in B0e--B2.5e Stars
• Evolution of the disk of pi Aqr: from near-disappearance to a strong maximum
• Non-adiabatic pulsations in ESTER models

Cited by in corpus (4)

• TESS lightcurves of gamma-Cas stars
• Short-term variability and mass loss in Be stars VI. Frequency groups in $\gamma$ Cas detected by TESS
• Automated photometry of $\gamma$ Cassiopeiae:the last roundup
• Irregular emission cycles in the Oe star HD 60848