Fast time optical variability in Be/X-ray binaries. Pulsation and rotation
arXiv:2209.06440 · doi:10.1051/0004-6361/202243664
Abstract
Classical Be stars, regardless of spectral subtype, display multiperiodic light modulations in the frequency range 0.1-12 d, when observed with high-cadence and long duration. This behaviour is attributed to non-radial pulsations and/or rotation of the Be star. The main goal of this work is to investigate the fast photometric variability of the optical counterparts to Be/X-ray binaries and compare the general patterns of such variability with the Galactic population of classical Be stars. We analyzed 21 sources with TESS. High-cadence photometry with two ground-based telescopes was also performed for 15 sources. Standard Fourier analysis and least-squares fitting methods were employed in the frequency analysis. All sources exhibit intra-night light variations with intensity variations of 0.01-0.06 mag in the ground-based observations and up to 5% in flux in TESS observations. This variability manifests itself as multi-periodic signals in the frequency range 0.2-12 d. We find that the patterns of variability of the Be stars in Be/X-ray binaries agree with that of classical early-type Be stars in terms of the general shape of the periodograms. Based on the general shape and number of peaks in the periodograms, Be/X-ray binaries can be classified into different types. The most common case is the presence of groups of closely-spaced frequencies (67%), followed by sources that exhibit isolated signals (18%). The remaining type of sources displays frequency spectra characterized by a mixed pattern of stochastic variability and high-frequency peaks. This study reveals that short-term optical photometric variability is a very common, if not ubiquitous, feature intrinsic to the Be optical companions in Be/X-ray binaries. This variability is mainly attributed to pulsations that originate in the stellar interior.
References in corpus (49)
- The Transiting Exoplanet Survey Satellite
- Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3
- The 3rd IBIS/ISGRI soft gamma-ray survey catalog
- Effects of gravitational darkening on the determination of fundamental parameters in fast rotating B-type stars
- INTEGRAL/IBIS all-sky survey in hard X-rays
- Low-frequency gravity waves in blue supergiants revealed by high-precision space photometry
- Signatures of internal rotation discovered in the Kepler data of five slowly pulsating B stars
- A unifying explanation of complex frequency spectra of gamma Dor, SPB and Be stars: combination frequencies and highly non-sinusoidal light curves
- A heuristic derivation of the uncertainty of the frequency determination in time series data
- Theory and evidence of global Rossby waves in upper main-sequence stars: r-mode oscillations in many Kepler stars
- Giant Outbursts in Be/X-ray Binaries
- Instability strips of SPB and beta Cephei stars: the effect of the updated OP opacities and of the metal mixture
- Unveiling the nature of INTEGRAL objects through optical spectroscopy. VI. A multi-observatory identification campaign
- Photometric detection of internal gravity waves in upper main-sequence stars. II. Combined TESS photometry and high-resolution spectroscopy
- INTEGRAL survey of the Cassiopeia region in hard X rays
- A new method for the spectroscopic identification of stellar non-radial pulsation modes. I. The method and numerical tests
- Joint H-alpha and X-Ray Observations of Massive X-Ray Binaries. II. The Be X-ray Binary and Microquasar LS I +61 303
- Distances to Galactic X-ray Binaries with Gaia DR2
- The Be/X-ray transient 4U 0115+63/V635 Cassiopeiae. III. Quasi-cyclic variability
- Swift/BAT and RXTE Observations of the Peculiar X-ray Binary 4U 2206+54 - Disappearance of the 9.6 Day Modulation
- Variability of newly identified B-type stars observed by Kepler
- Beta Cephei stars in the ASAS-3 data. II. 103 new Beta Cephei stars and a discussion of low-frequency modes
- A Pulsational Mechanism for Producing Keplerian Disks around Be Stars
- Long-term variability of high-mass X-ray binaries. I.Photometry
- Now you see it, now you don't - the circumstellar disk in the GRO J1008--57 system
- Discovery of slow X-ray pulsations in the high-mass X-ray binary 4U 2206+54
- The X-ray binary 2S0114+650=LSI+65 010:A slow pulsar or tidally-induced pulsations?
- Short-term variability and mass loss in Be stars II. Physical taxonomy of photometric variability observed by the Kepler spacecraft
- Be discs in binary systems: II. Misaligned orbits
- TESS observations of Be stars: a new interpretation
- Interferometric detections of sdO companions orbiting three classical Be stars
- Confirmation of a High Magnetic Field in GRO J1008-57
- Pulsating B and Be stars in the Small Magellanic Cloud
- On the cyclotron line in Cep X-4
- A photometric study of Be stars located in the seismology fields of COROT
- Optical counterpart to Swift J0243.6+6124
- Photometric variability of the Be star CoRoT-ID 102761769
- Long-term pulse profile study of the Be/X-ray pulsar SAX J2103.5+4545
- Recent activity of the Be/X-ray binary system SAX J2103.5+4545
- Short-term variability and mass loss in Be stars VI. Frequency groups in Cas detected by TESS
- Astrophysical parameters and orbital solution of the peculiar X-ray transient IGR J00370+6122
- Periodicities in the high-mass X-ray binary system RX J0146.9+6121/LS I+61 235
- Evidence for different accretion regimes in GRO J1008-57
- The gamma-ray source AGL J2241+4454 as the possible counterpart of MWC 656
- Optical variabilities in Be/X-ray binary system:GRO J2058+42
- Long-term optical and X-ray variability of the Be/X-ray binary H 1145-619: discovery of an on-going retrograde density wave
- Discovery of X-ray pulsations in the Be/X-ray binary IGR J21343+4738
- The optical counterpart to the Be/X-ray binary SAX J2239.3+6116
- Optical observations of Be/X-ray transient system KS 1947+300