Polarimetric constraints on the optical afterglow emission from GRB 990123

Polarization of the optical emission from GRB 990123 was measured on 24.17 January 1999 universal time with the Nordic Optical Telescope. An upper limit of 2.3% on the linear polarization was found. Accurate polarization measurements provide important clues to the blast wave geometry and magnetic field structure of gamma-ray bursts (GRBs). The lack of detectable polarization for GRB 990123 indicates that the optical afterglow was produced by a blast wave of unknown geometry with an insignificant coherent magnetic field or by a beamed outflow at high Lorentz factor seen at a small viewing angle. Such a collimated jet would help solve the problem of energy release in this exceptionally luminous cosmological burst.     

Recreational mapping and planning for enlargement of the green structure in greater Copenhagen

Since 1947, the development of greater Copenhagen has followed a plan that divided the city into a centre and five urban ‘fingers’. The ‘Finger Plan’ has constituted an important part of the planning framework, albeit informally. Under this plan, four green wedges and three green rings, located between the urban ‘fingers’, form a multifunctional recreational landscape of high value to the citizens. In 2006, the Greater Copenhagen Authority put forward a proposal for the enlargement of the existing green wedges and the addition of a new fourth green ring. In order to achieve this plan, detailed mapping of recreational opportunities was needed. Based on existing planning approaches combined with theoretical and empirical studies on preferences, use, and composition of green spaces, a method for monitoring and analyzing recreational experiences using seven specific categories was adapted and further developed to Danish conditions and applied to land use categories in greater Copenhagen. Areas that comprised one or more recreational experience values were designated by use of GIS techniques and map-based indicators for each of the seven ‘experience classes’ (wilderness; feeling of the forest; panoramic views, water, and scenery; biodiversity and land form; cultural history; activity and challenge; service and gathering). For incorporation into the regional and municipal planning policy, the seven experience classes were transformed into GIS, creating a decision support system for use at municipal and regional levels in order to facilitate future planning of the recreational landscape in greater Copenhagen. The method proved capable of pointing out important areas for recreational development in the enlarged but not yet developed areas. Further, the division of the recreational potential into seven classes makes possible site-specific development that utilizes existing potential.