Related papers: Pulsed Accretion onto Eccentric and Circular Binar…
We present results from a new code for binary black hole evolutions using the moving-puncture approach, implementing finite differences in generalised coordinates, and allowing the spacetime to be covered with multiple communicating…
Accreting X-Ray Binaries display a wide range of behaviours. Some of them are observed to spin up steadily, others to alternate between spin-up and spin-down states, sometimes superimposed on a longer trend of either spin up or spin down.…
The majority of massive stars reside in binary systems, which are expected to experience mass transfer during their evolution. However, so far the conditions under which mass transfer leads to a common envelope, and thus possibly to a…
This thesis describes a numerical study of binary boson stars within the context of an approximation to general relativity. The approximation we adopt places certain restrictions on the dynamical variables of general relativity (conformal…
Neutron stars in X-ray binary systems are fascinating objects that display a wide range of timing and spectral phenomena in the X-rays. Not only parameters of the neutron stars, like magnetic field strength and spin period evolve in their…
We present accretion rates for a large number of solar-type stars in the Cep OB2 region, based on U band observations. Our study comprises 95 members of the ~4 Myr-old cluster Tr 37 (including 20 "transition" objects; TO), as well as the…
It is well known that the accretion disk around a magnetized compact star can penetrate inside the magnetospheric boundary, so the magnetospheric radius $\ro$ does not represent the true inner edge $\rin$ of the disk; but controversies…
We explore test particle orbits in the orbital plane of eccentric stellar binary systems, searching for ``invariant loops'': closed curves that change shape periodically as a function of binary orbital phase as the test particles in them…
We have obtained 48 high resolution echelle spectra of the pre-main sequence eclipsing binary system KH~15D (V582 Mon, P = 48.37 d, $e$ $\sim$ 0.6, M$_{A}$ = 0.6 M$_{\odot}$, M$_{B}$ = 0.7 M$_{\odot}$). The eclipses are caused by a…
Numerical experiments are the primary method of studying the evolution of circumbinary disks due to the strong nonlinearities involved. Many circumbinary simulations also require the use of numerical mass sinks: source terms which prevent…
Thanks to long-term X-ray monitoring, a number of interacting binaries are now known to show X-ray periodicities on timescales of tens to hundreds of binary orbits. In some systems, precession of a warped accretion disc is the leading model…
We present the to-date largest parameter space exploration of binaries in circumbinary disks (CBDs), deriving orbital evolution prescriptions for eccentric, unequal mass binaries from our suite of hydrodynamic simulations. In all cases,…
Some accreting neutron stars and young stars show unexplained episodic flares in the form of quasi-periodic oscillations or recurrent outbursts. In a series of two papers we present new work on an instability that can lead to episodic…
Eclipsing binaries with pulsating components are a distinct subclass of binaries, merging orbital and pulsational analyses. In recent years, that subclass led to the definition of a newly formed branch of tidal asteroseismology. While…
Using zoom-simulations carried out with the adaptive mesh-refinement code RAMSES with a dynamic range of up to $2^{27} \approx 1.34 \times 10^8$ we investigate the accretion profiles around six stars embedded in different environments…
Accretion of planetary material onto host stars may occur throughout a star's life. Especially prone to accretion, extrasolar planets in short-period orbits, while relatively rare, constitute a significant fraction of the known population,…
The accretion process onto spinning objects in Kerr spacetimes is studied with numerical simulations. Our results show that accretion onto compact objects with Kerr parameter (characterizing the spin) $|a| < M$ and $|a| > M$ is very…
We report the detection of an anomalous accretion flare in the tight eccentric pre-main-sequence binary system DQ Tau. In a multi-epoch survey consisting of randomly acquired low to moderate resolution near-infrared spectra obtained over a…
We study the orbital evolution and accretion history of massive black hole (MBH) pairs in rotationally supported circumnuclear discs up to the point where MBHs form binary systems. Our simulations have high resolution in mass and space…
Nuclear burning and its dependence on the mass accretion rate are fundamental ingredients for describing the complicated observational phenomenology of neutron stars in binary systems. Motivated by high quality burst rate data emerging from…