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.

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

References in corpus (40)

• The Transiting Exoplanet Survey Satellite
• The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms
• The Lick Planet Search: Detectability and Mass Thresholds
• BRITE-Constellation: nanosatellites for precision photometry of bright stars
• Kepler observations of variability in B-type stars
• Exquisite Nova Light Curves from the Solar Mass Ejection Imager (SMEI)
• The X-ray emission of the gamma Cassiopeiae stars
• A Study of Pi Aquarii During a Quasi-normal Star Phase: Refined Fundamental Parameters and Evidence for Binarity
• The BRITE Constellation nanosatellite mission: Testing, commissioning and operations
• Using conditional entropy to identify periodicity
• A new method for the spectroscopic identification of stellar non-radial pulsation modes. II. Mode identification of the Delta Scuti star FG Virginis
• Hot stars observed by XMM-Newton II. A survey of Oe and Be stars
• A propelling neutron star in the enigmatic Be-star $\gamma$~Cassiopeia
• BRITE-Constellation: Data processing and photometry
• MOST detects SPBe pulsations in HD 127756 & HD 217543: Asteroseismic rotation rates independent of vsini
• Plaskett's Star: Analysis of the CoRoT photometric data
• Three discoveries of gamma Cas analogs from dedicated XMM-Newton observations of Be stars
• Short-term variability and mass loss in Be stars III. BRITE and SMEI satellite photometry of 28 Cygni
• Stellar parameters and H$\alpha$ line profile variability of Be stars in the BeSOS survey
• Short-term variability and mass loss in Be stars II. Physical taxonomy of photometric variability observed by the Kepler spacecraft
• Suzaku and NuSTAR X-Ray Spectroscopy of gamma Cas and HD110432
• TESS observations of Be stars: a new interpretation
• Discovery of Rapidly Moving Partial X-ray Absorbers within gamma Cassiopeiae
• The Remarkable Be Star HD110432
• On the X-ray and optical properties of the Be star HD 110432: a very hard-thermal X-ray emitter
• Doppler tomography of the circumstellar disk of π Aquarii
• BeppoSAX survey of Be/X-ray binary candidates
• Rotational and Cyclical Variability in gamma Cassiopeiae. II. Fifteen Seasons
• Variations of the amplitudes of oscillation of the Be star Achernar
• Short-term variability and mass loss in Be stars IV. Two groups of closely spaced, approximately equidistant frequencies in three decades of space photometry of $\nu$ Puppis (B7-8 IIIe)
• Short-term variability and mass loss in Be stars V. Space photometry and ground-based spectroscopy of $\gamma$ Cas
• Surprises in the simultaneous X-ray and optical monitoring of pi Aqr
• Chandra and Suzaku observations of the Be/X-ray star HD110432
• Characterization of the X-ray light curve of the gamma Cas-like B1e star HD110432
• Evidence of an asymmetrical Keplerian disk in the Brγ and He I emission lines around the Be star HD 110432
• 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
• Spectral Response of the Pulsationally-Induced Shocks in the Atmosphere of BW Vulpeculae

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