RUI: Pulsar Scintillation and the Interstellar Medium

Oberlin College, Oberlin OH

Investigators

Abstract

AST 0098561 Stinebring The scintillation, or intensity variation, of pulsars can be used to probe the interstellar medium on sizes similar to that of the Solar System. Since scintillation is caused by slight density variations in the ionized component of the interstellar gas, a detailed study of pulsar scintillation yields information about how the interstellar gas is clumped, whether or not it exhibits turbulence, and how the density variations are initiated and sustained. These questions are central to an understanding of the dynamics of our galaxy and, hence, of other spiral galaxies like ours. A dynamic spectrum is a sequential collection of radio spectra obtained, typically, at one minute intervals for several hours. Occasionally dynamic spectra exhibit a loosely organized crisscross pattern as well as the more typical random pattern due to multiple path scattering in the interstellar medium. Recently it has been shown that when harmonically analyzed this crisscross pattern has a distinct and well-delineated signature in transform space. Dr. Daniel Stinebring at Oberlin College will explore this phenomenon using high-sensitivity observations from the Arecibo radio telescope and the new fully steerable radio telescope in Green Bank, West Virginia. By seeing how the harmonic signature is curved in frequency and time, the location of the scattering material can be determined. From this and other details of the observations, the physical size of the scattering objects can be found. This will aid in understanding the physical nature of the scattering material and in linking it to other astrophysical phenomena such as supernova remnants or the turbulent outflow from very young or very old stars. Determining the frequency of occurrence of this phenomenon as well as its variation with radio frequency will give additional insights into its physical origin. This research program will involve undergraduate students in the excitement of exploring a new phenomenon and piecing together parts of a bigger puzzle: how does large scale stirring of the interstellar gas create small scale turbulence which is eventually dissipated as heat? By working closely with experienced researchers, the students will gain a broad range of technical skills as well as further develop their ability to independently explore problems. Using state-of-the-art electronics and computers at the largest radio telescopes in the world, the students will gain confidence in their ability to tackle large and complex problems. Opportunities to collaborate with scientists in the U.S. and abroad and to report their work at conferences and in publications will enhance students' research experience and prepare them for graduate training or other roles in the technical workforce. This award is made under the Research in Undergraduate Institutions program at NSF. ***