TESS observations of Be stars: a new interpretation

Abstract

Light curves of 57 classical Be stars in TESS sectors 1 - 15 are examined. In most Be stars, the periodogram shows groups at a fundamental and one or more harmonics, which we attribute to rotation. In about 40 percent of the stars, the group is just a single narrow or slightly broadened peak. In about 30 percent, it consists of a multiple, closely spaced peaks. These groups can be interpreted as non-coherent variations most likely associated with photospheric gas clouds. Approximate rotational frequencies for about 75 percent of the stars can be derived. Comparison with the projected rotational velocities shows that the photometric frequency is consistent with rotation. The first harmonic plays a prominent role in many Be stars and manifests itself in either single-wave or double-wave light curves. The reduction in amplitude of beta Cep pulsations in a few Be stars during an outburst and their subsequent recovery is most likely an obscuration effect. Other instances of possible obscuration of the photosphere are suspected. A simple model, which attempts to explain these observations and other general properties of Be stars, is proposed.

arXiv comment17 pages 17 figures 3 Tables

References in corpus (51)

• Gaia Data Release 2. Summary of the contents and survey properties
• The Gaia mission
• Intrinsic Colors, Temperatures, and Bolometric Corrections of Pre-Main Sequence Stars
• Dynamical Simulations of Magnetically Channeled Line-Driven Stellar Winds: I. Isothermal, Nonrotating, Radially Driven Flow
• A spectroscopic survey on the multiplicity of high-mass stars
• Be-star rotation: how close to critical?
• Sub-surface convection zones in hot massive stars and their observable consequences
• Rotational velocities of A-type stars IV. Evolution of rotational velocities
• Dynamical Simulations of Magnetically Channeled Line-Driven Stellar Winds: II. The Effects of Field-Aligned Rotation
• Dynamical Simulations of Magnetically Channeled Line-Driven Stellar Winds: III. Angular Momentum Loss and Rotational Spindown
• The MiMeS survey of magnetism in massive stars: Magnetic analysis of the O-type stars
• The spinning-top Be star Achernar from VLTI-VINCI
• Comparative statistics and origin of triple and quadruple stars
• Magnetic spots on hot massive stars
• A Statistical Study of Threshold Rotation Rates for the Formation of Disks around Be Stars
• Detection of additional Be+sdO systems from IUE spectroscopy
• Spectroscopic analysis of southern B and Be stars
• Variability Properties of 4 Million Sources in the $TESS$ Input Catalog Observed with the Kilodegree Extremely Little Telescope Survey
• Short-term variability and mass loss in Be stars I. BRITE satellite photometry of $\eta$ and $\mu$ Centauri
• The X-ray emission of the gamma Cassiopeiae stars
• A Multi-Membership Catalogue for 1876 Open Clusters using UCAC4 data
• Envelope Convection, Surface Magnetism and Spots in A- and late B-type Stars
• BRITE-Constellation high-precision time-dependent photometry of the early-O-type supergiant $\zeta$ Puppis unveils the photospheric drivers of its small- and large-scale wind structures
• Ejection velocities of high Galactic latitude runaway stars
• MONOS: Multiplicity Of Northern O-type Spectroscopic systems. I. Project description and spectral classifications and visual multiplicity of previously known objects
• MOBSTER - II. Identification of rotationally variable A stars observed with \emph{TESS} in Sectors 1 to 4
• MOST Detects g-Modes in the Late-Type be Star beta CMi (B8Ve)
• Rotational modulation in TESS B stars
• The Hot Companion and Circumbinary Disk of the Be Star HR 2142
• MOST detects corotating bright spots on the mid-O type giant ξ Persei
• Hot stars observed by XMM-Newton II. A survey of Oe and Be stars
• Accurate age determinations of several nearby open clusters containing magnetic Ap stars
• MOST detects SPBe pulsations in HD 127756 & HD 217543: Asteroseismic rotation rates independent of vsini
• 3D Stellar Reddening Map from 2MASS Photometry: An Improved Version
• 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
• The close-in companion of the fast rotating Be star Achernar
• The hot Gamma-Doradus and Maia stars
• Short-term variability and mass loss in Be stars II. Physical taxonomy of photometric variability observed by the Kepler spacecraft
• Exocomet signatures around the A-shell star $\Phi$ Leo?
• Evidence for spots on hot stars suggests major revision of stellar physics
• Disruption of circumstellar discs by large-scale stellar magnetic fields
• An investigation of the photometric variability of confirmed and candidate Galactic Be stars using ASAS-3 data
• Variations of the amplitudes of oscillation of the Be star Achernar
• Stellar parameters of Be stars observed with X-shooter
• 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)
• Spectro-interferometric observations of a sample of Be stars. Setting limits to the geometry and kinematics of stable Be disks
• Properties and nature of Be stars XXIII. Long-term variations and physical properties of kappa Dra
• Variable rotational line broadening in the Be star Achernar
• A new look into putative duplicity and pulsations of the Be star $\beta$ CMi
• Be Stars: Rapidly Rotating Pulsators

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• X-ray luminosity function of high-mass X-ray binaries: Studying the signatures of different physical processes using detailed binary evolution calculations
• $\nu$ Gem: a hierarchical triple system with an outer Be star
• The origin of early-type runaway stars from open clusters
• Short-term variability and mass loss in Be stars VI. Frequency groups in $\gamma$ Cas detected by TESS
• Properties of the Be-type stars in 30 Doradus
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• Populations of evolved massive binary stars in the Small Magellanic Cloud II: Predictions from rapid binary evolution
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