The Spin-period History of Intermediate Polars
J. Patterson, Enrique de Miguel, Jonathan Kemp, Shawn Dvorak, Berto Monard, Franz-Josef Hambsch, Tonny Vanmunster, David R. Skillman, D. Cejudo, Tut Campbell, George Roberts, J. L. Jones, Lewis M. Cook, Greg Bolt, Robert Rea, Joseph Ulowetz, Thomas Krajci, Kenneth Menzies, S. Lowther, William Goff, William Stein, M. A. Wood, Gordon Myers, G. Stone, H. Uthas, E. Karamehmetoglu, Jim Seargeant, J. McCormick
Abstract
Abstract We report the detailed history of spin-period changes in five intermediate polars (DQ Herculis, AO Piscium, FO Aquarii, V1223 Sagittarii, and BG Canis Minoris) during the 30–60 yr since their original discovery. Most are slowly spinning up, although there are sometimes years-long episodes of spin-down. This is supportive of the idea that the underlying magnetic white dwarfs are near spin equilibrium. In addition to the ∼40 stars sharing many properties and defined by their strong, pulsed X-ray emission, there are a few rotating much faster ( P < 80 s), whose membership in the class is still in doubt—and who are overdue for closer study.