The CGCA (The Leonard E. Parker Center for Gravitation, Cosmology and Astrophysics) seminars are scheduled for Fridays at 1:00 pm in in the Kenwood Interdisciplinary Research Complex (KIRC) Room KEN 2175. A “brown bag lunch” group will assemble in KEN 4118 (fourth floor kitchenette located next to the elevators) at 12:00 NOON.

The Strange Case of J1640+2224
Sarah Vigeland, University of Wisconsin-Milwaukee

Millisecond pulsars are powerful tools for studying astrophysics and gravity. Many of these studies involve fitting observed times of arrival (TOAs) to a complicated timing model that must take into account the astrometric, spin, and binary properties of the system. In this talk I will discuss a particular binary millisecond pulsar, PSR J1640+2224, for which there are several puzzles regarding the binary properties. Traditionally the timing model fit is done using linear least squares maximum estimation; however, recent analyses using Bayesian inference to do the fit yield results inconsistent with previous results. Additionally, there are optical observations of the white dwarf companion, which provide an independent estimate of the temperature and mass of the companion. I will discuss what all of these observations tell us about the identity of PSR J1640+2224 and its companion, and how we might be able to resolve some of these questions with future observations.