Radio observations were made with the National Radio Astronomy
Observatory, Very Large Array (VLA) at 1.5 and 4.9 GHz during 16 observing
sessions between 10 August and 30 September 1992. During this period the
VLA was in `D' configuration, yielding a synthesized beam width of
12
at 4.9 GHz and 40 at 1.5 GHz. The bandwidth of the
observations was 100 MHz.
The flux density scale was established
with reference to 3C48, for which flux densities of 15.2 and 5.3 Jy were
assumed at 1.5 and 4.9 GHz respectively. Monitoring of the complex
gains of the antennas was carried out with the secondary calibration sources,
0224+671 or 0212+735.
Measurements of the flux density were derived by making images of LSI+61 from each observing session. This was carried out using standard procedures within the Astronomical Image Processing System (AIPS). In all cases the emission from LSI+61 was unresolved. The rms noise levels on the maps was between 0.05 and 0.1 mJy. The uncertainties on the flux density measurements are dominated by calibration uncertainty, which is typically about 3%.
The results of the observations are shown in table 1. For the first 11 sessions, measurements were taken at 4.9 GHz, and on five of these occasions we also obtained nearly simultaneous data at 1.5 GHz. The final 5 observations were carried out at 1.5 GHz only. These data are plotted versus time in figure 1. The 1.5 GHz data span a period of 50 days, about two cycles of the 26.51 day radio period of LSI+61(Taylor & Gregory 1984). The flux densities trace out two consecutive outbursts from the star, and the beginning of a third. The 4.9 GHz data span one orbital period, and show the evolution of the first outburst with more detail. These data cover the period of the x-ray observations.