C. E. Petry

TL;DR: The LSST design is driven by four main science themes: probing dark energy and dark matter, taking an inventory of the solar system, exploring the transient optical sky, and mapping the Milky Way.

TL;DR: The Large Synoptic Survey Telescope (LSST) as discussed by the authors is a large, wide-field ground-based system designed to obtain repeated images covering the sky visible from Cerro Pachon in northern Chile.

Abstract: Gamma-ray bursts (GRBs) are thought to arise when an extremely relativistic outflow of particles from a massive explosion (the nature of which is still unclear) interacts with material surrounding the site of the explosion. Observations of the evolving changes in emission at many wavelengths allow us to investigate the origin of the photons, and so potentially determine the nature of the explosion. Here we report the results of γ-ray, optical, infrared, submillimetre, millimetre and radio observations of the burst GRB990123 and its afterglow. Our interpretation of the data indicates that the initial and afterglow emissions are associated with three distinct regions in the fireball. The peak flux of the afterglow, one day after the burst, has a lower frequency than observed for other bursts; this explains the short-lived radio emission. We suggest that the differences between bursts reflect variations in the magnetic-field strength in the afterglow-emitting regions.

TL;DR: In this article, the authors used an automated software to detect and identify the lines, almost all of which are unresolved at the Goddard High Resolution Spectrograph (GHRS) of the Hubble Space Telescope (HST).

TL;DR: In this article, the spectra of the four components are virtually identical, although there are differences among the Lyα emission-line equivalent widths that might be due to microlensing.