Can the Rapid Braking of the White Dwarf in AE Aquarii Be Explained in Terms of the Gravitational-Wave Emitter Mechanism?
The spin-down power of the white dwarf in the close binary AE Aquarii significantly exceeds the bolometric luminosity of the system. The interpretation of this phenomenon in terms of the gravitational-wave emitter mechanism has been recently suggested by Choi & Yi. The basic assumption of their interpretation is that the spatially limited blobs or mounds of mass δm ~ 10-3 M☉ are present at the magnetic poles of the white dwarf. We show that the mounds of this mass can be confined by the magnetic field of the white dwarf only if the dipole magnetic moment of the star exceeds 4 × 1037 G cm3. Under these conditions, however, the magnetodipole losses of the white dwarf would exceed the evaluated spin-down power by 6 orders of magnitude. On this basis, we discard the possibility that the observed rapid braking of the white dwarf in AE Aqr can be explained in terms of the mechanism proposed by Choi & Yi.
The discovery of a brake on the white dwarf in AE Aquarii.
We report the discovery of a rapid spindown of the 33-s rotation period of the white dwarf in AE Aqr at a steady rate of 5.64×10 −14 s s −1 over a baseline of at least 14.5 yr. The newly derived orbital period by Welsh, Horne & Gomer is confirmed, and it is shown that the secondary star's absorption-line radial velocities provide the correct phasing for the 33-s oscillations if they originate at the white dwarf. The amplitude of the pulse-timing delays, a wd sin i=2.04 s, yields a white dwarf mass of between 0.9 and 1.0 M ○. . The spindown power of the white dwarf is −IΩΩ˙=6×10 33 I 50 erg s −1 , which exceeds the accretion luminosity of AE Aqr by a factor of ∼120
A search for TeV emission from AE Aquarii
Abstract We have observed the cataclysmic variable AE Aqr for a total of 68.7 hours over the epoch 1991–1995 using the Whipple Observatory 10 m gamma-ray telescope. An analysis of these data has revealed no evidence for any steady, pulsed or episodic TeV emission. We have calculated an upper limit for steady emission of 4.0 × 10−12 photons cm−2s−1 at an energy threshold of 900 GeV. This is three orders of magnitude less than the flux reported by others during burst activity. Our upper limits coherent pulsed emission at the first and second harmonics of the white dwarf frequency are 1.5 × 10−12 photons cm−2s−1 in each case.