A Multi-Frequency Study of Arecibo Pulsars

Timothy Eugene Edward Olszanski, University of Vermont


Compact Objects (Neutron Stars) form in the last moments of a star's life, during the violent events known as supernovae. As the star's core fusion falters, matter undergoes a dramatic gravitational compression resulting in internal densities rivaling subatomic particles. Ever since their discovery in the mid-twentieth century, these highly magnetized and rapidly rotating balls of condensed matter have provided a bountiful playground for astronomers seeking out exotic physics.

Neutron Stars that emit electromagnetic radiation are seen by observers as Pulsars, named such for the pulse of intensity as the pulsar's radiation beam passes into our line of sight. These beams are comprised of two unique regions with differing phenomenology; core emission that arises close to the pulsar polar cap and centered within the radiation beam, and higher altitude conal emission that lies along the beam's periphery.

While pulsars can and do emit over a wide frequency range, most known pulsars are seen as radio sources, at sensitivities where studies of the pulsar single-pulses allows us to probe the rich details of the plasma-filled pulsar magnetosphere. Even then, the radio emission often has a steep spectra, restricting the frequencies in which radio telescopes can study pulsars.

We have utilized the unmatched sensitivity of Arecibo Observatory to conduct a multi-frequency single-pulse survey, between 327 MHz and the novel 4.5 GHz, of Arecibo's brightest high-frequency pulsars. The broad frequency range and single-pulse resolutions have allowed us to set accurate beam classifications for these nearly two dozen pulsars while extending constraints on important population trends to higher frequencies.

Several of the pulsars in our survey exhibit deviant behavior, and are thus useful as followup case studies to further our understanding of pulsar radio emission. One of the most interesting cases involves pulsar B0823+26, where we find evidence for an age-dependent death-line separating core and conal dominated pulsars, suggesting that the plasma generating capabilities of a pulsar changes as they age.

For the other three, they fall in the ``Partial Cone'' class; a type of pulsar that is characterized by strong delays in their emission. We find that all three of these pulsars show evidence of core emission.