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
Selective etching of InP in NaF solution
Abstract The crossing porous structure of InP has been obtained by electrochemical etching in NaF solutions. The behavior of the periodic oscillation occurs at different potential ranges for the different concentrations of solutions, and it will disappear with the concentration of the solution decreased. The scanning electron microscope (SEM) image shows that the pores have two directions on the surface and are perpendicular to each other. The two directions are assigned to [0 1 1] and [ 0 1 ¯ 1 ], respectively. The SEM image of the cross-section also shows that the two directions are assigned to [1 1 1]B and [ 1 1 ¯ 1 ¯ ]B. Both are due to the selective etching of F− ions. The crossing porous structure of InP is a very promising feature for the three-dimensional structure of III–V compound semiconductors for photonic band gap materials.