Dynamic in situ optical and magneto-optical monitoring of the growth of Co-Pd multilayers

In situ ellipsometry and Kerr polarimetry have been used to follow the continuous evolution of the optical and magneto- optical properties of multiple layers of Co and Pd during their growth. Films were sputter deposited onto a Pd buffer layer on glass substrates up to a maximum of N = 10 bi-layer periods according to the scheme glass/Pd(10)Ar x (0.3Co/3Pd) (nm). Magnetic hysteresis measurements taken during the deposition consistently showed strong perpendicular anisotropy at all stages of film growth following the deposition of a single monolayer of Co. Magneto-optic signals associated with the normal-incidence polar Kerr effect indicated strong polarization of Pd atoms at both Co-Pd and Pd-Co interfaces and that the magnitude of the complex magneto-optic Voigt parameter and the magnetic moment of the Pd decrease exponentially with distance from the interface with a decay constant of 1.1 nm(- 1). Theoretical simulations have provided an understanding of the observations and allow the determination of the ultrathin- film values of the elements of the skew-symmetric permittivity tensor that describe the optical and magneto-optical properties for both CO and Pd. Detailed structure in the observed Kerr ellipticity shows distinct Pd-thickness-dependent oscillations with a spatial period of about 1.6 nm that are believed to be associated with quantum well levels in the growing Pd layer.

A J-band detection of the sub-stellar mass donor in SDSS J1433+1011

We present time-resolved J-band spectroscopy of the short-period cataclysmic variable SDSS J143317.78+101123.3. We detect absorption lines from the sub-stellar donor star in this system, which contributes 38 +/- 5 per cent to the J-band light. From the relative strengths of the absorption lines in the J band, we estimate the spectral type of the donor star to be L2 +/- 1. These data are the first spectroscopic detection of a donor with a confirmed sub-stellar mass in a cataclysmic variable, and the spectral type is consistent with that expected from semi-empirical evolutionary models.

Using skew mapping, we have been able to derive an estimate for the radial velocity of the donor of K-d = 520 +/- 60 km/s. This value is consistent with, though much less precise than, predictions from mass determinations found via photometric fitting of the eclipse light curves.

Testing the efficacy of the glacial buzzsaw: insights from the Sredinny Mountains, Kamchatka

Peak altitudes, hypsometry, geology, and former equilibrium-line altitudes (ELAs) are analyzed across the Sredinny Mountains (Kamchatka). Overall, evidence is found to suggest that the glacial buzzsaw has operated to shape the topography of this mountain range, but the strength of this signature is not spatially uniform. In the southern sector of the mountains, we see evidence that an efficient glacial buzzsaw has acted to impose constraints upon topography, limiting peak altitudes, and concentrating land-surface area (hypsometric maxima) close to palaeo-ELAs. By contrast, in the northern sector of the mountains, a number of peaks rise high above the surrounding topography, and land-surface area is concentrated well below palaeo-ELAs. This deviation from a classic ‘buzzsaw signature’, in the northern sector of the mountains, is considered to reflect volcanic construction during the Quaternary, resulting in a series of high altitude peaks, combined with the action of dynamic glaciers, acting to skew basin topography toward low altitudes, well below palaeo-ELAs. These glaciers are considered to have been particularly dynamic because of their off-shore termination, their proximity to moisture-bearing air masses from the North Pacific, and because accumulation was supplemented by snow and ice avalanching from local high altitude peaks. Overall, the data suggest that the buzzsaw remains a valid mechanism to generally explain landscape evolution in mountain regions, but its signature is significantly weakened in mountain basins that experience both volcanic construction and climatic conditions favouring dynamic glaciation.

The not-so-extreme white dwarf of the CV GD 552

GD 552 is a cataclysmic binary which was previously believed to be composed of an M-star and a white dwarf, the latter having an extreme mass of 1.4 solar masses. In a recent paper we showed that this is not compatible with new observational evidence and presented an alternative model in which the white dwarf has a typical mass and the companion is a brown dwarf, making the system a likely member of the elusive group of CVs which have already evolved through minimum orbital period. Here we present additional spectroscopical evidence supporting this conclusion by means of skew mapping.