Related papers: A natural explanation for periodic X-ray outbursts…
We present a new scenario for the behaviour of Be/X-ray binaries based on long-term multiwavelength monitoring and the decretion disc model. The circumstellar discs of the primaries are truncated because of the tidal and resonant effect of…
Be/X-ray binary systems exhibit both periodic (Type I) X-ray outbursts and giant (Type II) outbursts, whose origin has remained elusive. We suggest that Type II X-ray outbursts occur when a highly misaligned decretion disk around the Be…
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…
Type I outbursts in Be/X-ray binaries are usually associated with the eccentricity of the binary orbit. The neutron star accretes gas from the outer parts of the decretion disk around the Be star at each periastron passage. However, this…
With three-dimensional hydrodynamical simulations we show that the size of the decretion disc and the structure of the accretion flow onto the neutron star in a Be/X-ray binary strongly depends upon the disc aspect ratio, $H/R$. We simulate…
Be star X-ray binaries are transient systems that show two different types of outbursts. Type I outbursts occur each orbital period while type II outbursts have a period and duration that are not related to any periodicity of the binary…
Type I Be/X-ray binary outbursts are driven by mass transfer from a Be star decretion disc to a neutron star companion during each orbital period. Treiber et al. (2021) recently observed non-periodic type I outbursts in RX J0529.8-6556 that…
We present multi-wavelength long-term monitoring observations of V635 Cas, the optical counterpart to the transient X-ray pulsar 4U0115+63. The evolution of emission lines and photometric magnitudes indicates that the Be star undergoes…
Be stars are surrounded by outflowing circumstellar matter structured in the form of decretion discs. They are often members of binary systems, where it is expected that the decretion disc interacts both radiatively and gravitationally with…
As the largest population of high mass X-ray binaries, Be/X-ray binaries provide an excellent laboratory to investigate the extreme physics of neutron stars. It is generally accepted that Be stars possess a circumstellar disc, providing an…
Superorbital periods that are observed in the brightness of Be/X-ray binaries may be driven by a misaligned and precessing Be star disc. We examine how the precessing disc model explains the superorbital variation of (i) the magnitude of…
We study the viscous effects on the interaction between the coplanar Be-star disc and the neutron star in Be/X-ray binaries, using a three-dimensional, smoothed particle hydrodynamics code. For simplicity, we assume the Be disc to be…
The purpose of this work is to review the observational properties of Be/X-ray binaries. The open questions in Be/X-ray binaries include those related to the Be star companion, that is, the so-called "Be phenomenon", such as, timescales…
A review of basic properties of Be/X-ray binaries is presented. These systems (called also hard X-ray transients), which form the most numerous class of massive X-ray binaries in the Galaxy, are composed of Be stars and neutron stars (X-ray…
Giant outbursts of Be/X-ray binaries may occur when a Be-star disc undergoes strong eccentricity growth due to the Kozai-Lidov (KL) mechanism. The KL effect acts on a disc that is highly inclined to the binary orbital plane provided that…
Rapidly rotating Be stars are observed as shell stars when the decretion disc is viewed edge on. Transitions between the two implies that the discs may be warped and precessing. Type II X-ray outbursts are thought to occur when the warped…
We investigate the spectroscopic characteristics of the optical components of Be/X-ray binary systems, using data collected during our seven-year monitoring campaign. We find examples of major changes in the emission line profiles…
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…
We probe models of disc truncation in the hard spectral state of an outburst of the well-known X-ray transient GX 339--4. We test a large number of different models of disc reflection and its relativistic broadening, using two independent…
Recent observations have shown that circumstellar and circumbinary discs in young stellar binaries are often misaligned with respect to the binary orbital plane. We analyze the tidal truncation of such misaligned discs due to torques…