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, XMM-Newton and Chandra X-ray observations spread over 10yr; 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 P = 3.46(56) x 10 -19 d -1 , which is inconsistent in sign and magnitude with magnetic dipole radiation losses, or an additional quadratic term with P = 2.0(1.0) x 10 -15 d d -1 , 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.