Models of Planets and Brown Dwarfs in Mira Winds

We present numerical hydrodynamical models of the effects of planets or brown dwarfs orbiting within the extended atmosphere and wind formation zone of Mira variables. We find time-dependent wake dynamics and episodic accretion phenomena which may give rise to observable optical events and affect SiO maser emission.Comment: 4 pages, 3 figures, follow-up to JAAVSO pape

Genetic optimization for radio interferometer configurations

The large bandwidth and resolution specifications of today’s telescopes require the use of different types of collectors positioned over long baselines. Innovative feeds and detectors must be designed and introduced in the initial phases of development. The required level of resolution can only be achieved through a ground-breaking configuration of dishes and antennas. This work investigates the possibility of the genetic optimization of radio interferometer layouts given constraints on cable length, required UV density distribution and point-spread function. Owing to the large collecting area and the frequency range required for the Square Kilometre Array (SKA) to deliver the promised science, the configuration of the dishes within each station is an important issue. As a proof of concept, the Phase 1 specifications of this telescope are used to test the proposed framework.peer-reviewe

Advances in POST2 End-to-End Descent and Landing Simulation for the ALHAT Project

Program to Optimize Simulated Trajectories II (POST2) is used as a basis for an end-to-end descent and landing trajectory simulation that is essential in determining design and integration capability and system performance of the lunar descent and landing system and environment models for the Autonomous Landing and Hazard Avoidance Technology (ALHAT) project. The POST2 simulation provides a six degree-of-freedom capability necessary to test, design and operate a descent and landing system for successful lunar landing. This paper presents advances in the development and model-implementation of the POST2 simulation, as well as preliminary system performance analysis, used for the testing and evaluation of ALHAT project system models

Continuous and Burst-like Accretion onto Substellar Companions in Mira Winds

We present numerical hydrodynamical modeling of the effects of a giant planet or brown dwarf companion orbiting within the extended atmosphere and wind formation zone of an approximately solar-mass Mira variable star. The large-scale, time-dependent accretion flows within the radially oscillating and outflowing circumstellar gas around Miras are related to Bondi-Hoyle-Lyttleton flows, but have not, to our knowledge, been previously modelled. The new models presented in this paper illustrate the changes in accretion and wake dynamics as the companion mass is varied over a range from 10 to 50 Jupiter masses ($M_J$). The character of the accretion onto the companion changes greatly as the companion mass is increased. At the lowest companion masses considered here, a low continuous rate of mass accretion is punctuated by large, nearly periodic bursts of accretion. When the companion mass is large, the mass accretion has both a continuous part, and a rapidly varying, nearly stochastic part. These trends can be understood as the result of the interplay between the shocks and radial oscillations in the circumstellar gas, and the wake flow behind the companion. Models with accretion bursts may produce observable optical brightenings, and may affect SiO maser emission. (Abridged)Comment: 16 pgs., 10 figures with low resolution versions of Figs. 1, 9. Accepted for publication in MNRA