Abstracts

Sebastien Hess

Title

Modeling the radio signature of the orbital parameters, rotation, and magnetic field of exoplanets

Abstract

Since the first extra-solar planet discovery in 1995, several hundreds of these planets have been discovered. Most are hot Jupiters, i.e. massive planets orbiting close to their star. These planets may be powerful radio emitters. We simulate the radio dynamic spectra resulting from various interaction models between an exoplanet and its parent star, i.e. exoplanet-induced stellar emission and three variants of the exoplanet's magnetospheric auroral radio emission (full auroral oval, active sector fixed in longitude, and active sector fixed in local time). We show the physical information about the system that can be drawn from radio observations, and how this can be achieved. This information includes the magnetic field strength and the rotation period of the emitting body (planet or star), the orbital period, the orbit's inclination, and the magnetic field tilt relative to the rotation axis or offset relative to the center of the planet. For most of these parameters, radio observations provide a unique means of measuring them. Our results should provide the proper framework of analysis and interpretation for future detections of radio emissions from exoplanetary systems -- or from magnetic white dwarf-planet or white dwarf-brown dwarf systems --, that are expected to commence soon as part of extensive programs at large radiotelescopes such as LOFAR, UTR2 or the GMRT. Our methodology can be easily adapted to simulate specific observations, once effective detection is achieved.

Rachel Osten

Title

Constraints on Low Frequency Emission from Brown Dwarfs

Abstract

Ultracool dwarfs occupy the region of parameter space intermediate in mass and temperature between stars and planets. The masses and temperatures of those objects which display detectable levels of cm-wavelength radio emission are closer to the stellar than the planetary regime, however the radio properties of some of these objects are more similar to the solar system giant planets. The rotationally modulated emission seen at cm-wavelengths has been interpreted as an electron cyclotron maser operating close to the surface of the star. The coincidence of emission at both 3.6 and 6 cm has been further interpreted as evidence of masing conditions in different parts of the atmosphere. We performed a series of observations at 330 MHz targeting two well known ultracool dwarfs which exhibit periodic radio emission, in order to explore the nature of the low frequency radio emission. We discuss the constraints which our upper limits provide on the plasma environment and the requirements for future observations to make advances in understanding the magnetic nature of ultracool dwarfs.

Bart Scheers

Title

Towards a Dynamic LOFAR Catalogue

Abstract

LOFAR will observe tens of millions of sources. Most of the sources will be revisited many times every second, whereas millions of measurements of the same source are no exception. I will present the state of the current framework for detecting transient and variable sources.
Furthermore, I will discuss the distributed database system in which all the LOFAR measurements for all the sources detected by LOFAR can be appended and accessed: the light-curve database. This system is frequently updated with the latest LOFAR observations. Up-to-date sky models are retrieved from here as well.

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