Radio Pulse Properties of the Millisecond Pulsar Psr J0437[4715. I. Observations at 20 Centimeters

We present a total of 48 minutes of observations of the nearby, bright millisecond pulsar PSR J0437[4715 taken at the Parkes Observatory in Australia. The data were obtained at a central radio frequency of 1380 MHz using a high-speed tape recorder that permitted coherent Nyquist sampling of 50 MHz of bandwidth in each of two polarizations. Using the high time resolution available from this voltage recording technique, we have studied a variety of single-pulse properties, many for the Ðrst time in a millisecond pulsar. We show that individual pulses are broad band, have pulse widths ranging from D10 in pulse longitude) to D300 ks (D20¡) with a mean pulse width of D65 ks (D0¡.6 (D4¡), exhibit a wide variety of morphologies, and can be highly linearly polarized. Single pulse peaks can be as high as 205 Jy (over D40 times the average pulse peak), and have a probability distribution similar to those of slow-rotating pulsars. We observed no single pulse energy exceeding D4.4 times the average pulse energy, ruling out ““ giant pulses ÏÏ as have been seen for the Crab and PSR B1937]21 pulsars. PSR J0437[4715 does not exhibit classical microstructure or show any signs of a preferred timescale that could be associated with primary emitters ; single pulse modulation has been observed to be consistent with amplitude-modulated noise down to timescales of 80 ns. We observe a signiÐcant inverse correlation between pulse peak and width. Thus, the average pulse proÐle produced by selecting for large pulse peaks is narrower than the standard average proÐle. We Ðnd no evidence for ““ di†ractive ÏÏ quantization e†ects in the individual pulse arrival times or amplitudes as have been reported for this pulsar at lower radio frequency using coarser time resolution. Overall, we Ðnd that the single-pulse properties of PSR J0437[4715 are similar to those of the common slow-rotating pulsars, even though this pulsarÏs magnetosphere and surface magnetic Ðeld are several orders of magnitude smaller than those of the general population. The pulsar radio emission mechanism must therefore be insensitive to these fundamental neutron star properties. Subject headings : pulsars : individual (J0437[4715) È radio continuum: stars È stars : neutron