Related papers: One-armed oscillations in Be star discs
Be stars are a class of rapidly rotating B stars with circumstellar disks that cause Balmer and other line emission. There are three possible reasons for the rapid rotation of Be stars: they may have been born as rapid rotators, spun up by…
We present long term H$\alpha$ monitoring results of five Be/X-ray binaries to study the Be disc size variations and their influence on Type II (giant) X-ray outbursts. The work is done in the context of the viscous decretion disc model…
The B0.5IVe star gam Cas is of great interest because it is the prototype of a small group of classical Be stars having hard X-ray emission of unknown origin. We discuss results from ongoing B and V observations of the gam Cas star-disk…
The effect of gravitational darkening on models of the thermal structure of Be star disks is systematically studied for a wide range of Be star spectral types and rotation rates. Gravitational darkening causes a reduction of the stellar…
We present recent contemporaneous X-ray and optical observations of the Be/X-ray binary system A\,0535+26 with the \textit{Fermi}/Gamma-ray Burst Monitor (GBM) and several ground-based observatories. These new observations are put into the…
Scattered light images of transition discs in the near-infrared often show non-axisymmetric structures in the form of wide-open spiral arms in addition to their characteristic low-opacity inner gap region. We study self-gravitating discs…
There is an increasing body of evidence that suggests that Be disks are well described by the Viscous Decretion Disk (VDD) model according to which the formation and structure of the disk depend on the kinematic viscosity of the gas.…
Superorbital periods are observed in the optical light curves of many Be/X-ray binaries yet their origin has remained somewhat elusive. We suggest that precession of the spin axis of the Be star can drive superorbital periods, particularly…
Although the star itself is not He enriched, the periodicity and the variability in the UV wind lines of the pulsating B1 IV star beta Cep are similar to what is observed in magnetic He-peculiar B stars, suggesting that beta Cep is…
We present the results of three-dimensional simulations of the deep convective envelope of a young (10 Myr) one-solar-mass star, obtained with the Anelastic Spherical Harmonic code. Since young stars are known to be faster rotators than…
We examine Be star discs in highly eccentric Be/X-ray systems. We use a three-dimensional smoothed particle hydrodynamics (SPH) code to model the structure of the Be star disc and investigate its interactions with the secondary star over…
Context. Be stars are physically complex systems that continue to challenge theory to understand their rapid rotation, complex variability and decretion disks. $\gamma$ Cassiopeiae ($\gamma$ Cas) is one such star but is even more curious…
We present the results of our monitoring program to study the long-term variability of the Halpha line in high-mass X-ray binaries. We have carried out the most complete optical spectroscopic study of the global properties of high-mass…
Spectroscopic, polarimetric, and high spectral resolution interferometric data covering the period 1995-2011 are analyzed to document the transition into a new phase of circumstellar disk activity in the classical Be-shell star 48 Lib. The…
The late-type Be star $\beta$ CMi is remarkably stable compared to other Be stars that have been studied. This has led to a realistic model of the outflowing Be disk by Klement et al. These results showed that the disk is likely truncated…
The Be star $\pi$ Aquarii shows peculiar $\gamma$ Cas-type X-ray emission, likely caused by its outer disk interacting with a low-mass companion, probably a white dwarf. We study the long-term variability of its optical spectra to derive…
We present a numerical model describing a circularly symmetric gaseous disk around the Be star chi Ophiuchi. The model is constrained by long-baseline interferometric observations that are sensitive to the H-alpha Balmer line emission from…
The gamma-ray binary system PSR B1259-63 consists of a 48 ms pulsar orbiting a Be star. The system is particularly interesting because it is the only gamma-ray binary system where the nature of the compact object is known. The non-thermal…
Context. HD 110432 was classified as a "\gamma Cas X-ray analog" since it has similar peculiar X-ray and optical characteristics, i.e. a hard-thermal X-ray variable emission and an optical spectrum affected by an extensive disk. Lopes de…
We investigate the intrinsic continuum linear polarization from axisymmetric density distributions of gas surrounding classical Be stars during the formation and dissipation of their circumstellar disks. We implement a Monte Carlo…