With its two stellar eclipses and two disk attenuations per binary orbit, V658 Carinae stands out as the first clear eclipsing Be + sdOB system. This rare alignment offers a unique opportunity to probe the structure and dynamics of a Be star disk with unprecedented detail. In this study, we present the most comprehensive observational data set and modeling effort for this system to date, including optical, near-infrared, and ultraviolet spectroscopy, space-based photometry, and optical polarization. Using a new ray-tracing code, we apply a three-component model, consisting of an oblate, rapidly rotating Be star, a symmetric circumstellar disk, and a compact stripped companion, to reproduce the system’s light curve, polarization, and spectral features. Our analysis yields precise constraints on the stellar and disk parameters, determining its status as the second-known late-type Be + stripped star, and also provides strong spectroscopic evidence for a tenuous circumsecondary envelope. Despite the model’s overall success, several key observables, such as the H _α equivalent width and the secondary attenuation, remain poorly reproduced, pointing to the need for more sophisticated modeling. In particular, future improvements should incorporate the companion’s radiative feedback on the disk and account for asymmetric disk structures expected by the gravitational interaction with the companion. Owing to its unique geometry and rich diagnostics, V658 Car establishes itself as a benchmark system for Be stars (and rapid rotators in general), stripped stars, post-RLOF massive binaries, and circumstellar disk structures.

We present a detailed analysis of the early post-mass-transfer binary system HD 698 (V742 Cas), combining high-resolution optical spectroscopy, long-baseline interferometry, and radiative transfer modeling. Counter-phased RV curves reveal a circular orbit with a period of 55.927 +/- 0.001 d and component masses of MBe = 7.48 +/- 0.07 M circle dot and Mcomp = 1.23 +/- 0.02 M circle dot. The Be primary is traced via broad H alpha wings, while narrow metallic absorption lines originate from a slowly rotating companion. The angular separation measured via interferometry implies a dynamical distance of 888 +/- 5 pc. The spectral energy distribution is best reproduced with a color excess E(B - V) = 0.321 +/- 0.016 due to interstellar reddening and a moderately dense viscous decretion disk with base density rho 0 similar or equal to 5 x 10-12 g cm-3 at r = Req, declining radially as rho(r) proportional to r-n with n = 3.0. The companion is found to be a luminous and inflated star with Teff,comp=10.0-0.1+0.2 kK, Rcomp=13.1-0.2+0.2R circle dot , and logL/L circle dot=3.19 , contributing significantly to the flux (Lcomp/LBe similar to 0.3). Spectral line mismatches provide further circumstantial evidence that the companion is hydrogen poor, consistent with a stripped-envelope star enriched by CNO processing. HD 698 thus belongs to the emerging class of Be + bloated O/B binaries, representing a short-lived, high-luminosity post-mass-transfer phase, when the stripped donor is still spectroscopically detectable before reaching the subdwarf phase.

Be stars are characterized by the presence of a circumstellar Keplerian disk formed from material ejected from the rapidly rotating stellar surface. This article presents recent observational and theoretical progress on two central aspects of this phenomenon: the mechanisms driving mass loss, and the fate of the ejected material. Using simultaneous TESS photometry and ground-based spectroscopy, we examine the short-term variability associated with discrete mass ejection events, or “flickers”, and review strong evidence linking them to pulsational activity near the stellar surface. Complementary 3D hydrodynamic simulations reproduce key observational signatures and establish that disk formation requires compact and asymmetric ejection sites with sufficient angular momentum to overcome re-accretion. In systems with binary companions, new high-resolution simulations resolve the outer disk for the first time and identify five dynamically distinct regions, including a circumsecondary disk and a circumbinary spiral outflow. Together, these results provide a coherent framework that traces the full life cycle of disk material from pulsation-driven ejection near the stellar surface to its final destination, whether re-accreted by the companion or lost from the system entirely.

Angular momentum transport is a fundamental process shaping the structure, evolution, and lifespans of stars and disks across a wide range of astrophysical systems. Be stars offer a valuable environment for studying viscous transport of angular momentum in massive stars, thanks to their rapid rotation, observable decretion disks, and likely absence of strong magnetic fields. This study analyzes angular momentum loss in 40 Be binary simulations spanning a range of orbital separations and companion masses, using a smoothed-particle hydrodynamics (SPH) code. A novel framework is introduced to define the outer disk edge based on the behaviour of the azimuthal velocity, streamlining the analysis of angular momentum transport within the system. Applying this framework reveals that systems with smaller truncation radii tend to reaccrete a larger fraction of their angular momentum during dissipation, thereby inhibiting the stars ability to regulate its surface rotation. Modification of this rate may alter the star’s mass-injection duty cycle or long-term evolutionary track. Finally, a subset of the simulations were post-processed using the Monte Carlo radiative transfer code HDUST, generating synthetic observables including H α line profiles, V-band polarization, and UV polarization. Suggestions for observational verification of the dynamical results are demonstrated using the simulated data.

We conduct a systematic study on the effects of rapid rotation on predicted Be star observables. We use the three-dimensional Monte Carlo radiative transfer code, hdust, to model a comprehensive range of Be star subtypes at varying rotation rates. Using these models, we predict V magnitude and photometric color, Hα line profiles, and polarization at UV wavelengths as well as in the V-band for Be stars from B0 to B8. For each spectral subtype, we investigate the effects of disk density on the produced observables. We find that reddening and brightening effects of gravity darkening may cause rapidly-rotating stars to appear more evolved than they truly are. Rotational effects on the Hα line profile shape may reduce line intensity for Be stars viewed at low inclinations and increase line intensity for those viewed at high inclinations. Additionally, rapid rotation can significantly impact the measured equivalent width of the line produced by a star with a moderate to high density disk, especially at high inclinations. When the star-disk system is viewed near edge-on, gravity darkening can result in stronger Hα emission than would otherwise be expected for a disk of a given density. We also find that the competing effects of rapid rotation and H i opacity cause the slope of the polarized continuum (the polarization color) to be very sensitive to changes in the stellar rotation rate. This quantity offers a strong diagnostic for the rotation rate of Be stars.

Multicolor OGLE survey light curves of about 20 yr duration are analyzed for about 3000 classical Be stars in the Large and Small Magellanic Clouds (LMC, SMC) in order to study their properties and variability. Each light curve was manually analyzed to distinguish between different scenarios, such as photospheric baseline levels and disk buildup and dissipation phases. This analysis was aided by dynamical disk models and photospheric models to coarsely determine the inclination angle and mass. Measured quantities such as the fraction of time spent actively ejecting mass (the duty cycle (DC)), the fraction of time spent with a detectable disk (the disk duty cycle (DDC)), the buildup and dissipation time of isolated disk events, and the number of mass outbursts per year allow us to characterize and compare the behavior of the two populations. There is a wide spread in the DC, with median values of 0.44 (LMC) and 0.60 (SMC). The DDC is high for both populations, with median values of 0.99 (LMC) and 1.0 (SMC), indicating that disks are almost always present for these stars. The occurrence rate of outbursts ranges from zero to about two per year, with median values of 0.31 (LMC) and 0.26 (SMC). There are strong statistical differences in the behavior of the LMC and SMC populations, with the lower metallicity stars being more active in terms of their DC and DDC, and with less frequent but longer-lasting outbursts.

NGC 7419 is a young open cluster notable for hosting five red supergiants and a high abundance of Classical Be (CBe) stars. CBe stars are main-sequence non-supergiant B-type stars that exhibit or have exhibited Balmer-line emissions in their spectra. We perform a membership analysis using Gaia DR3 data and machine learning techniques like Gaussian mixture models and Random Forest and determine the cluster's mean distance to be 3.6(-0.6)(+1.0) kpc. We identify 499 Gaia-based members with a mass above similar to 1.2 M-circle dot, and estimate the cluster's age to be 21.1(-0.6)(+1.6) Myr. Using our revised H alpha excess-based analysis, we find 42 CBe stars containing many known CBe stars, bringing the total number of CBe stars in NGC 7419 to 49 and the fraction of CBe to (B + CBe) members to 12.7 per cent. We investigate the variability of the candidate members from Zwicky Transient Facility and NEOWISE data using standard deviation, median absolute deviation, and Stetson index (J), and their periodicity using the Generalized Lomb-Scargle periodogram variability. We find that 66 per cent of CBe stars are variable: 23 per cent show periodic signals, typical of pulsation/rotation, 41 per cent display variability characteristic of disc dynamics or binarity, and 14 per cent exhibit long-term changes, consistent with disc dissipation/formation. We also find that all pulsating CBe stars are early-type, while 50 per cent of stars with long-term variations are early-type, and the other 50 per cent are mid-type. Our results agree with previous findings in the literature and confirm that CBe stars display variability through multiple mechanisms across different time-scales.

V658 Car is the first known eclipsing binary system involving a classical Be star and an sdOB companion, offering a unique opportunity to study disk physics and binary interactions in unprecedented detail. From TESS data and multi-color observations from the comissão para a colaboração entre profissionais e amadores collaboration, we analyze the system’s color–magnitude diagram and compare it with radiative transfer models that include the Be star, its circumstellar disk, and the sdOB companion. While the stellar eclipses are well reproduced, two features observed in the multi-color photometry challenge the current modeling paradigm: the discrepancy between the observed reddening and the modeled blueing during the first attenuation phase and the complete lack of modeled attenuation around the second stellar eclipse. These issues highlight the need for more sophisticated modeling approaches to capture the complex interplay between disk opacity and binary dynamics.

ABSTRACT The viscous decretion disc (VDD) scenario has been used to model the observables of the Be stars. Its capability to predict individual observables has been confirmed for several Be stars. Here, we simultaneously analyse the spectroscopic and $BVI$-band photometric data for the Be star MT91-213 with the Monte Carlo radiative-transfer code hdust to determine the stellar parameters, geometry, and physical conditions for its circumstellar disc. MT91-213 is the primary component of a binary system whose companion is the pulsar PSR J2032+4127. We find that the VDD model can simultaneously reproduce the multiple observables qualitatively, but not quantitatively. We determine the mass of the primary star to be 13.1 ${\rm M}_{\odot }$ which is smaller than reported in the literature. We present a dynamical scenario for the evolving disc density from a diffuse to a dense phase. Also, we determine that the inclination of the disc is about 40$^{\circ }$ which means it is 20$^{\circ }$ tilted from the orbit of the secondary star. Our results indicate that the mass loss rate for MT91-213 is $\sim 10^{-7}$ to $10^{-6} {\rm M}_{\odot }\,\mathrm{yr}^{-1}$ which is in agreement with the suggested values in the literature, required to explain the observed X-ray synchrotron luminosity, $L_\mathrm{x}$, for PSR J2032+4127.

Classical Be stars are rapidly rotating B type stars that are surrounded by a gaseous circumstellar decretion disk. Like many massive stars, Be stars are frequently found to exist in binary systems, with a wide array of orbital configurations. Recently, we have computed three- dimensional (3D) smoothed particle hydrodynamics (SPH) models of Be stars with equal-mass binary companions whose orbit is misaligned to the initial plane of the disk and found that the misaligned companion can cause the disk to undergo phenomena of Kozai–Lidov oscillations, and disk-tearing, in addition to the expected tilting and warping of the disk. We now show that these phenomena are not unique to equal-mass systems, but that there is a range of mass ratios for which disk-tearing and Kozai–Lidov oscillations can occur. We also find that an increase in viscosity can suppress these phenomena. Next, we combine our SPH models with the 3D nonlocal thermodynamic equilibrium Monte Carlo radiative transfer code HDUST to produce synthetic spectra of these systems. We show how both phenomena can change the Hα emission line profile, and how disk-tearing creates a detectable polarization signature. We also present a comparison of the observable trends in our disk-tearing model, and how these mimic the changes observed in Pleione (28 Tau). Overall our results demonstrate how phenomena from a misaligned binary companion can cause variations in observables across the whole disk, and that these phenomena need to be considered when analyzing the time evolution of Be star spectra.

B[e] supergiants (sgB[e]) are rare objects whose evolutionary stage remains uncertain. Observationally, they display strong Balmer emission lines, infrared excess, and intrinsic polarization, indicating a non-spherical circumstellar envelope. We present a study of the sgB[e] RMC 82, using new spectropolarimetric data complemented by photometry from the ultraviolet (UV) to the mid-infrared. Our two-component model comprises a slow, dense equatorial wind wherein dust grains form and a fast polar wind. We applied the hdust radiative transfer code and Bayesian statistics to infer the parameters from a grid of 3240 pre-computed models. The model accurately reproduces the spectral energy distribution and polarized spectrum, but struggles to match the H alpha emission. Our results suggest a large mass-loss rate of 6.6 x 10(-6)M (R) yr(-1) sr(-1). The dense wind is confined within an opening angle of 11 degrees. The hottest dust grains are located at 277R(*) with a temperature of 870 K. The dust grains are porous, with a density of 0.051 g cm(-3). The central star was found to be significantly hotter than previous estimates (T-eff = 27 000 K). By comparing models with different components, we find that gas reprocesses a significant amount of UV radiation, shielding the dust. Ho we ver, the dust also scatters UV photons back to the inner disc, increasing its temperature and H alpha emission. We conclude that self-consistent models, that account for the gas-dust interplay in the envelope, are essential for studying sgB[e] and similar objects.

Recent simulations of Be stars in misaligned binary systems have revealed that misalignment between the disc and binary orbit can cause the disc to undergo Kozai-Lidov (KL) oscillations or disc-tearing. We build on our previous suite of three-dimensional smoothed particle hydrodynamics simulations of equal-mass systems by simulating eight new misaligned Be star binary systems, with mass-ratios of 0.1 and 0.5, or equal-mass systems with varying viscosity. We find the same phenomena occur as previously for mass ratios of 0.5, while the mass ratio of 0.1 does not cause KL oscillations or disc-tearing for the parameters examined. With increased viscosity in our equal-mass simulations, we show that these phenomena and other oscillations are damped out and do not occur. We also briefly compare two viscosity prescriptions and find they can produce the same qualitative disc evolution. Next, we use the radiative transfer code HDUST to predict observable trends of a KL oscillation, and show how the observables oscillate in sync with disc inclination and cause large changes in the polarization position angle. Our models generate highly complex line profiles, including triple-peak profiles that are known to occur in Be stars. The mapping between the SPH simulations and these triple-peak features gives us hints as to where they originate. Finally, we construct interferometric predictions of how a gap in the disc, produced by KL oscillations or disc-tearing, perturbs the visibility versus baseline curve at multiple wavelengths, and can cause large changes to the differential phase profile across an emission line.

H α emission is a clear indicator of circumstellar activity in Be stars, historically employed to assess the classical Be star (CBe) population in young open clusters (YOCs). The YOC NGC 330 in the Small Magellanic Cloud exhibits a large known fraction of CBe stars and was selected for a pilot study to establish a comprehensive methodology for identifying H α emitters in the Magellanic Clouds, encompassing the entire B-type spectral range. Using the SOAR Adaptive Module Imager (SAMI), we investigated the stellar population of NGC 330 using multiband BVRI +H α imaging. We identified H α emitters within the entire V -band range covered by SAMI/SOAR observations ( V ≲ 22), comprising the complete B-type stellar population and offering a unique opportunity to explore the Be phenomenon across all spectral subclasses. The stellar radial distribution shows a clear bimodal pattern between the most massive (B5 or earlier) and the lower mass main-sequence objects (later than B6) within the cluster. The former is concentrated toward the cluster center (showing a dispersion of σ = 4.26 ± 0.20 pc), whereas the latter extends across larger radii ( σ = 10.83 ± 0.65 pc), indicating mass stratification within NGC 330. The total fraction of emitters is 4.4% ± 0.5%, notably smaller than previous estimates from flux- or seeing-limited observations. However, a higher fraction of H α emitters is observed among higher mass stars (32.8% ± 3.4%) than within lower mass (4.4% ± 0.9%). Consequently, the putative CBe population exhibits distinct dynamical characteristics compared to the bulk of the stellar population in NGC 330. These findings highlight the significance of the current observations in providing a complete picture of the CBe population in NGC 330.

We examine the evolution of the disk surrounding the Be star in the highly eccentric 10.8 yr binary system δ Scorpii over its three most recent periastron passages. V -band and B − V photometry, along with H α spectroscopy, are combined with a new set of extensive multiband polarimetry data to produce a detailed comparison of the disk's physical conditions during the time periods surrounding each closest approach of the secondary star. We use the three-dimensional Monte Carlo radiative transfer code HDUST and a smoothed particle hydrodynamics code to support our observations with models of disk evolution, discussing the behavior of the H α and He i 6678 Å lines, V -band magnitude, and polarization degree. We compare the characteristics of the disk immediately before each periastron passage to create a baseline for the unperturbed disk. We find that the extent of the H α emitting region increased between each periastron passage, and that transient asymmetries in the disk become more pronounced with each successive encounter. Asymmetries of the H α and He i 6678 Å lines in 2011 indicate that perturbations propagate inward through the disk near periastron. When the disk’s direction of orbit is opposite to that of the secondary, the parameters used in our models do not produce spiral density enhancements in the H α emitting region because the tidal interaction time is short due to the relative velocities of the disk particles with the secondary. The effects of the secondary star on the disk are short-lived and the disk shows independent evolution between each periastron event.

ABSTRACT We build on our previous work involving smoothed particle hydrodynamic simulations of Be stars, by using the model that exhibited disc tearing as input into the three-dimensional Monte Carlo radiative transfer code hdust to predict observables from a variety of viewing angles throughout the disc tearing process. We run one simulation at the start of each orbital period from 20 to 72 orbital periods, which covers two complete disc tearing events. The resulting trends in observables are found to be dependent on the relative position of the observer and the tearing disc. The H $\rm \alpha$ equivalent width, V magnitude, and polarization can all increase or decrease in any combination depending on the viewpoint of the observer. The H $\rm \alpha$ line profile also displays changes in strength and peak separation throughout the tearing process. We show how the outer disc of the torn system can have a large effect on the H $\rm \alpha$ line profile, and also contributes to a wavelength-dependent polarization position angle, resulting in a similar sawtooth shape to the polarization percentage. Finally, we compare our predictions to Pleione (28 Tau) where evidence has suggested that a disc tearing event has occurred in the past. We find that our tearing disc model can broadly match the trends seen in Pleione’s observables, as well as produce the two-component H $\rm \alpha$ lines observed in Pleione. This is the strongest evidence, thus far, of Pleione’s disc having indeed experienced a tearing event.

The observations of all known major activity phases of the disks around the classical Be stars γ Cas and 59 Cyg with low-mass companions are comprehensively reviewed and purely qualitatively evaluated again, though taking advantage of new insights gained over the past 25 yr into the physics of Be disks. Both stars have exhibited activity cycles in the violet-to-red (V/R) flux ratio of emission lines with two peaks. This activity is indistinguishable from those of the vast majority of Be stars and so probably were caused by one-armed ( m = 1) disk oscillations. The anomalous high-activity phases from 1932 to 1942 in γ Cas and between 1972 and 1976 in 59 Cyg were distinguished from m = 1 density waves by large variations in the separations of pairs of emission peaks. In two consecutive cycles, shell phases during which the emission peaks were maximally separated alternated with single (blended) emission peaks. The amplitude in peak separation of more than a factor of two implies a high-amplitude variation in the disk aspect angle. When the peaks were blended and the disk was viewed closest to face-on, local maxima in visual brightness probably occurred in γ Cas, and the visibility of the stellar absorption lines was reduced, as is expected from increased free-bound emission into the line of sight (there is no time-resolved photometry for 59 Cyg from the event in the 1970s). In y Cas, the pre-event V/R variability (pre-event observations of 59 Cyg do not exist) was practically identical to m = 1 variability. In spite of the subsequent rapid rise in amplitude (up to ~4), the V/R variations connected smoothly in phase but may require an explanation involving the 3D structure of the disk. The phasing of single-peak and shell stages relative to the V/R activity was the same in both cycles of γ Cas, whereas this is not clear for 59 Cyg. During both high-activity cycles of γ Cas, but at different phases, transient additional pairs of emission lines appeared in γ Cas that were much sharper than the main ones and they also had different peak separations and V/R ratios. In the second instance, their velocities were up to ~+500 km s −1 . The extremely rapid excitation of the activity phases and their short duration of only two cycles in both stars may indicate a resonant behavior of an unidentified nature. In both stars, the line emission was strongly developed at the onset of the high-activity phases but it basically disappeared at the end of them, and the disks may have been dynamically destroyed. The atypical disk variations were presumably triggered by enhanced interactions between a disk and companion star. In both systems, there seems to be less evidence for a mass-loss outburst than for a reduced mass-injection rate into the disk. The resulting lower viscous coupling between a disk and star would have facilitated the tilting of the disk.

ABSTRACT We use the three-dimensional Monte Carlo radiative transfer code hdust to model Be stars where the disc is tilted from the equatorial plane of the star. We compute 128 models across four spectral types, B0, B2, B5, and B8, tilting the disc by 0, 10○, 20○, and 40○, respectively, while varying disc density according to spectral type. We also compute every model for an average and high stellar rotation rate. We first discuss non-tilted disc temperatures and show its nonlinear dependence on stellar and disc parameters. We find that tilting the disc minimally affects the density-weighted average disc temperature, but tilting does create a temperature asymmetry in disc cross-sections, which is more pronounced for a faster rotation rate. We also investigate the effect tilting has on V-band magnitude, polarization, and the H$\rm \alpha$ line. Tilting the disc does affect these observables, but the changes are entirely dependent on the position of the observer relative to the direction of tilt. We find the observables that distinguish tilting from a change in density or geometry are the H$\rm \alpha$ line shapes, where it can transition between single-peaked and double-peaked, and the polarization position angle, whose value is dependent on the projected major elongation axis of the disc on the sky. We also present one early- and one late-type model with warped discs. We find their temperature structure varies a small amount from the uniformly tilted models, and the different observables correspond to different tilt angles, consistent with their expected volume of origin within the disc.

ABSTRACT Classical B emission (Be) stars are fast rotating, near-main-sequence B-type stars. The rotation and the presence of circumstellar discs profoundly modify the observables of active Be stars. Our goal is to infer stellar and disc parameters, as well as distance and interstellar extinction, using the currently most favoured physical models for these objects. We present BeAtlas, a grid of $61\, 600$ non-local thermodynamic equilibrium radiative transfer models for Be stars, calculated with the hdust code. The grid was coupled with a Monte Carlo Markov chain (MCMC) code to sample the posterior distribution. We test our method on two well-studied Be stars, α Eri and β CMi, using photometric, polarimetric, and spectroscopic data as input to the code. We recover literature determinations for most of the parameters of the targets, in particular the mass and age of α Eri, the disc parameters of β CMi, and their distances and inclinations. The main discrepancy is that we estimate lower rotational rates than previous works. We confirm previously detected signs of disc truncation in β CMi and note that its inner disc seems to have a flatter density slope than its outer disc. The correlations between the parameters are complex, further indicating that exploring the entire parameter space simultaneously is a more robust approach, statistically. The combination of BeAtlas and Bayesian-MCMC techniques proves successful, and a powerful new tool for the field: The fundamental parameters of any Be star can now be estimated in a matter of hours or days.

Light scattered off particles can become linearly polarized. Stars surrounded by oblique, co-rotating envelopes are therefore expected to manifest periodic linear polarimetric variations. The electron scattering magnetospheres of magnetic massive stars are expected to be suitable candidates to observe this effect. In this paper, we present the first semi-analytical model capable of synthesizing the continuum polarimetric signatures of magnetic O-type stars in an optically thin, single electron scattering limit. The purpose of this investigation is to improve our general understanding of magnetic hot stars by characterizing their polarimetric behaviour. Our linear polarization model is constructed by combining the analytical expressions for the polarimetric variations of an obliquely rotating envelope with the Analytic Dynamical Magnetosphere model to represent a physical model for the envelope density structure. We compute grids of model Stokes $Q$ and $U$ curves and show that their shapes are unique to the choice of inclination and obliquity angles. We apply our model to HD 191612, a prototypical Of?p-type star, having both polarimetric and photometric observations. We find that the polarimetric modulations are best reproduced with $i=19^{+12}_{-3}$$^\circ$, $\beta=71^{+3}_{-9}$$^\circ$, and $\log \dot{M}_{B=0}=-6.11^{+0.12}_{-0.06}$ [M$_{\odot}$ yr$^{-1}$]. These results agree with previous investigations of this star. By combining both polarimetric and photometric synthesis tools, we simultaneously model the observations thus adding further refinement of the wind and magnetic properties of HD 191612.

We use a three-dimensional smoothed particle hydrodynamics code to simulate growth and dissipation of Be star discs in systems where the binary orbit is misaligned with respect to the spin axis of the primary star. We investigate six different scenarios of varying orbital period and misalignment angle, feeding the disc at a constant rate for 100 orbital periods, and then letting the disc dissipate for 100 orbital periods. During the disc growth phase, we find that the binary companion tilts the disc away from its initial plane at the equator of the primary star before settling to a constant orientation after 40-50 orbital periods. While the mass-injection into the disc is ongoing, the tilting of the disc can cause material to reaccrete on to the primary star prematurely. Once disc dissipation begins, usually the disc precesses about the binary companion's orbital axis with precession periods ranging from 20 to 50 orbital periods. In special cases, we detect phenomena of disc tearing, as well as Kozai-Lidov oscillations of the disc. These oscillations reach a maximum eccentricity of about 0.6, and a minimum inclination of about 20 degrees with respect to the binary's orbit. We also find the disc material to have highly eccentric orbits beyond the transition radius, where the disc changes from being dominated by viscous forces, to heavily controlled by the companion star, in contrast to its nearly circular motion inwards of the transition radius. Finally, we offer predictions to how these changes will affect Be star observables.