Hope College Physics Department
Research Experiences for Undergraduates
Summer 2009
Project Summary

 

Project Title: Peak Analysis of Radio and Gamma-Ray Pulse Profiles
Student Name: Joshua Roberts
Student's Home Institution: Hope College
Research Advisor: Dr. Peter Gonthier
Source of Support: This effort was generously supported by the Michigan Space Grant Consortium, and by the NASA Astrophysics Theory and Fundamental Program..

A peak-finding algorithm is developed to analyze the pulse profiles of simulated normal radio and gamma-ray pulsars to study the characteristics of the profiles and the correlations that exist between the radio and gamma-ray pulse profiles. NASA’s new Fermi Gamma-ray Space Telescope (Fermi) launched in June of 2008 has already discovered over 40 new gamma-ray pulsars adding significantly to the six previously known. Recent observations by Fermi suggest that the high-energy emission is from regions high in the magnetosphere near the pulsar light cylinder from the last open field surface. Both high-altitude emission models, the “Slot Gap” (polar cap) model and the “Outer Gap” model, are able to produce similar shaped pulse profiles. We explore the statistics of the gamma-ray peak separation and the radio lag in time form the gamma-ray peak as possible signatures that might aid in the discrimination between these two models. The algorithm smoothes the pulse profiles to eliminate noise and then takes first and second derivatives to identify the significant peaks. Preliminary results suggest that the slot gap model produces a large number of profiles with larger peak separations than the outer gap model with somewhat different characteristics in a plot as a function of the spin-down energy for both radio-loud and radio-quiet/weak Fermi simulated pulsars.

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