SIMULTANEOUS OBSERVATIONS OF GIANT PULSES FROM PULSAR PSR B0950+08 AT 42 AND 74 MHz

Abstract

We report the detection of giant pulse (GP) emission from PSR B0950+08 in 12 hr of observations made simultaneously at 42 and 74 MHz, using the first station of the Long Wavelength Array. We detected 275 GPs (in 0.16% of the pulse periods) and 465 GPs (0.27%) at 42 and 74 MHz, respectively. The pulsar is weaker and produces less frequent GPs than at 100 MHz. Here, GPs are taken as having 10 times the flux density of an average pulse (AP); their cumulative distribution of pulse strength follows a power law, with an 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 GPs detected within the same periods from both 42 and 74 MHz, which means more than half of them are not generated in a wide band. The CLEAN-based algorithm was used to deconvolve the the effect of scattering broadening and we have concluded that the scattering effect from the interstellar medium at 42 and 74 MHz is weak and cannot be distinguished from the pulse profiles. 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 AP, while for GPs, r (42 MHz) = 29.10 km (0.241% of R LC ) and r (74 MHz) = 28.95 km (0.240% of R LC ). GPs, which have a double-peak structure, have a smaller mean peak-to-peak separation compared to the AP.