The White Dwarf in AE Aqr Brakes Harder

Abstract

Taking advantage of the very precise de Jager et al. optical white dwarf orbit and spin ephemerides; ASCA, XMMN, and Chandra X-ray observations spread over 10 yrs; and a cumulative 27 yr baseline, we have found that in recent years the white dwarf in AE Aqr is spinning down at a rate that is slightly faster than predicted by the de Jager et al. spin ephemeris. At the present time, the observed period evolution is consistent with either a cubic term in the spin ephemeris with Pdouble_dot = 3.46(56)E-19 per d, which is inconsistent in sign and magnitude with magnetic-dipole radiation losses, or an additional quadratic term with Pdot = 2.0(1.0)E-15 d/d, which is consistent with a modest increase in the accretion torques spinning down the white dwarf. Regular monitoring, in the optical, ultraviolet, and/or X-rays, is required to track the evolution of the spin period of the white dwarf in AE Aqr.