We report the detection of giant pulse emission from PSR~B0950+08 in 12 hours of observations made simultaneously at 42~MHz and 74~MHz, using the first station of the Long Wavelength Array, LWA1. We detected 275 giant pulses (in 0.16% of the pulse periods) and 465 giant pulses (0.27%) at 42 and 74~MHz, respectively. The pulsar is weaker and produces less frequent giant pulses than at 100~MHz. Here, giant pulses are taken as having $geq$ 10 times the flux density of an average pulse; their cumulative distribution of pulse strength follows a power law, with a index of $-$4.1 at 42~MHz and $-$5.1 at 74~MHz, which is much less steep than would be expected if we were observing the tail of a Gaussian distribution of normal pulses. We detected no other transient pulses in a wide dispersion measure range from 1 to 5000~pc~cm$^{-3}$. There were 128 giant pulses detected within in the same periods from both 42 and 74~MHz, which means more than half of them are not generated in a wide band. We use CLEAN-based algorithm to analyze the temporal broadening and conclude that the scattering effect from the interstellar medium can not be observed. We calculated the altitude $r$ of the emission region using the dipolar magnetic field model. We found $r$(42~MHz) = 29.27~km ($0.242%$ of $R_{LC}$) and $r$(74~MHz) = 29.01~km ($0.240%$ of $R_{LC}$) for the average pulse, while for giant pulses, $r$(42~MHz) = 29.10~km ($0.241%$ of $R_{LC}$) and $r$(74~MHz) = 28.95~km ($0.240%$ of $R_{LC}$). Giant pulses, which have a double-peak structure, have a smaller mean peak-to-peak separation compared to the average pulse.
تحميل البحث