Concepts in Thermal Physics 2nd Edition
, 2012
The Dynamics and Stability of Circumbinary Orbits
Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 418:4 (2011) 2656-2668
Abstract:
We numerically investigate the dynamics of orbits in 3D circumbinary phase-space as a function of binary eccentricity and mass fraction. We find that inclined circumbinary orbits in the elliptically-restricted three-body problem display a nodal libration mechanism in the longitude of the ascending node and in the inclination to the plane of the binary. We (i) analyse and quantify the behaviour of these orbits with reference to analytical work performed by Farago & Laskar (2010) and (ii) investigate the stability of these orbits over time. This work is the first dynamically aware analysis of the stability of circumbinary orbits across both binary mass fraction and binary eccentricity. This work also has implications for exoplanetary astronomy in the existence and determination of stable orbits around binary systems.The non-thermal emission of extended radio galaxy lobes with curved electron spectra
ArXiv 1111.4878 (2011)
Abstract:
The existing theoretical framework for the energies stored in the synchrotron-emitting lobes of radio galaxies and quasars doesn't properly account for the curved spectral shape that many of them exhibit. We characterise these spectra using parameters that are straightforwardly observable in the era of high-resolution, low-frequency radio astronomy: the spectral curvature and the turnover in the frequency spectrum. This characterisation gives the Lorentz factor at the turnover in the energy distribution (we point out that this is distinctly different from the Lorentz factor corresponding to the turnover frequency in a way that depends on the amount of curvature in the spectrum) and readily gives the equipartition magnetic field strength and the total energy of the radiating plasma obviating the need for any assumed values of the cutoff frequencies to calculate these important physical quantities. This framework readily yields the form of the X-ray emission due to inverse-Compton (IC) scattering of Cosmic Microwave Background (CMB) photons by the electrons in the plasma having Lorentz factors of $\sim$1000. We also present the contribution to CMB anisotropies due to relativistic plasmas such as giant radio galaxy lobes, expressed in terms of the extent to which the lobes have their magnetic field and particle energies are in equipartition with one another.The inverse-Compton ghost HDF130 and the giant radio galaxy 6C0905+3955: Matching an analytic model for double-lobed radio source evolution
Monthly Notices of the Royal Astronomical Society 417:2 (2011) 1576-1583