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Research Interests



  • Astrophysics

As GLAST approaches launch at the end of the year or early next year, improved population studies of radio and gamma-ray pulsars predicting the numbers and characteristics of gamma-ray pulsars expected to be detected are at a crucial stage.

We continue to make progress with the issues associated with the radio beam geometry and intrinsic physical luminosity model of neutron stars that are necessary ingredients for a population synthesis. We are attempting to constrain the viewing geometry of radio pulsars whose profiles contain distinct core and conal components. This study was presented at a recent workshop at NRAO in Green Bank, WV, where our efforts were applauded, and we received a great deal of encouragement from radio astronomers. In fact, it was decided that we will have a population synthesis and a profile fitting challenge. There was a concerted effort to bring together groups who were doing similar studies to interact closely and understand differences and similarities of the outcome of these studies. We believe that this summer, we will be able to have a much better handle on the beam geometry and luminosity.

In addition, Sarah Story spearheaded an effort to develop the code for the population study of millisecond pulsars. We were able to obtain reasonable results with a common radio beam geometry and luminosity model for both normal and millisecond pulsars. This study has recently been submitted to ApJ with Sarah as being the lead author.

The training aspects of this project have been with undergraduate students from Hope College in part funded by the NSF-REU and NSF-RUI program. Students from Hope involved this past year have been: Sarah Story and Brian Clow. We traveled to Goddard for a 4-week stay to collaborate with Alice Hardin, during which we attended various seminars give by a variety of scientists and worked along the side of NASA scientists. We took our own computers and made significant progress. The rest of the 10-week program was spent at Hope College with Hope students. We also attended conferences and gave several presentations.

We continue to develop our program to study the population statistics of radio and gamma-ray pulsars comparing the detected and predicted statistics as observed by various instruments. When AGILE and GLAST are launched, there needs to be an expectation of numbers of radio-quiet and radioloud, gamma-ray pulsars they will observe. We hope that such observations will constrain models that describe the acceleration of electrons and the region in which it takes place. Our studies also help to constrain and define the radio emission geometry of pulsars by pointing out the need for further refinement, which we are currently undertaking. We are providing assistance to the GLAST team with normal and millisecond pulsars as gamma-ray sources for them to test their analysis software.

This summer I mentored an education student, Stephanie Allen, who has obtained funding from the Howard Hughes Medical Institute (internal grant). She obtained a physics major with secondary education certification to teach physics in high school and has developed a series of astronomy modules centered on the topic of gamma-ray bursts to use in the classroom after the students take their AP exam to inform and enthuse students. Steph was able to put together a manual of what and how she intends to use the program she developed. She presented her work at various meetings throughout the year.