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Abstract. We present radio, millimeter and optical observations of the afterglow of GRB 030329. UBVR C I C photometry is presented for a period of 3 h to 34 days after the burst. Radio monitoring at 1280 MHz has been carried out using the GMRT for more than a year. Simultaneous millimeter observations at 90 GHz and 230 GHz have been obtained from the Swedish-ESO Submillimeter Telescope (SEST) and the IRAM-PdB interferometer over more than a month following the burst. We use these data to constrain the double jet model proposed by for this afterglow. We also examine whether instead of the two jets being simultaneously present, the wider jet could result from the initially narrow jet, due to a fresh supply of energy from the central engine after the "jet break".

Received; accepted 1 send preprint requests to ygupta@ncra.tif r.res.in -2 -ABSTRACT Refraction of pulsar radiation by electron density irregularities in the interstellar medium sometimes produces multiple imaging of pulsars which can lead to periodic oscillations of intensity in pulsar dynamic spectra records. Such events can be used as tools to resolve the emission regions in pulsar magnetospheres. Here we describe results from the recent observation of a double imaging event for PSR B1133+16, which place fairly tight constraints on the location of the emission regions. Our analysis constrains the location of the scattering object to the shell of the Local Bubble. The phase of the oscillations shows significant variations across the pulse. The minimum value for the transverse separation of the emitting regions at the two edges of the pulse is inferred to be 3 × 10 5 m. This translates to a minimum emission altitude of 2.6 × 10 6 m. The non-monotonic variations of the fringe phase with pulse longitude are interpreted as variations of the altitude of the emission regions for the orthogonal polarization modes of this pulsar. This is in agreement with theories where propagation effects, such as refraction, are responsible for the orthogonal modes.