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 the mass \delta m ~ 10^{-3} M_sun, 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 4x10^{37} G cm^3. Under these conditions, however, the magnetodipole losses of the white dwarf would exceed the evaluated spin-down power 6 orders of magnitude. On this basis we discard a possibility that the observed rapid braking of the white dwarf in AE Aquarii can be explained in terms of the mechanism proposed by Choi & Yi.Comment: 6 pages, published in ApJ, 576, L5

A new look at spherical accretion in High Mass X-ray Binaries

Currently used model of spherical accretion onto a magnetized rotating neutron star encounters major difficulties in explaining the entry rate of accreting material into the stellar field and spin evolution of long-period X-ray pulsars. These difficulties can be, however, avoided if the magnetic field of the material captured by the neutron star is incorporated into the model. The magnetic field of the flow itself under certain conditions controls the accretion process and significantly affects the parameters of the accreting material. The mode by which the accretion flow enters the stellar magnetosphere in that case can be associated with Bohm (or turbulent) diffusion and the torque applied to the neutron star appears to be substantially higher than that evaluated in the non-magnetized accretion scenario.Comment: published in Proc. of WISAP 2011 Conference 'Waves and Instabilities in Space and Astrophysical Plasmas', P.-L. Sulem & M. Mond (eds.), Eilat, Israel, June 19-24, 201

Spectropolarimetric Observations of Herbig Ae/Be Stars. II. Comparison of Spectropolarimetric Surveys: HAeBe, Be and Other Emission-Line Stars

The polarization of light across individual spectral lines contains information about the circumstellar environment on very small spatial scales. We have obtained a large number of high precision, high resolution spectropolarimetric observations of Herbig Ae/Be, Classical Be and other emission-line stars collected on 117 nights of observations with the HiVIS spectropolarimeter at a resolution of R=13000 on the 3.67m AEOS telescope. We also have many observations from the ESPaDOnS spectropolarimeter at a resolution of R=68000 on the 3.6m CFH telescope. In roughly ~2/3 of the so-called "windy" or "disky" Herbig Ae/Be stars, the detected H-alpha linear polarization varies from our typical detection threshold near 0.1% to over 2%. In all but one HAe/Be star the detected polarization effect is not coincident with the H-alpha emission peak but is detected in and around the obvious absorptive part of the line profile. The qu-loops are dominated by the polarization in this absorptive region. In several stars the polarization varies in time mostly in the absorptive component and is not necessarily tied to corresponding variations in intensity. This is a new result not seen at lower resolution. In the Be and emission-line stars, 10 out of a sample of 30 show a typical broad depolarization effect but 4 of these 10 show weaker effects only visible at high resolution. Another 5 of 30 show smaller amplitude, more complex signatures. Six stars of alternate classification showed large amplitude (1-3%) absorptive polarization effects. These detections are largely inconsistent with the traditional disk-scattering and depolarization models.Comment: Published in ApJS 180. 47 pages, 34 figures. Small corrections made to tex