The Period Changes of the Cepheid RT Aurigae

Observations of the light curve for the 3.7-day Cepheid RT Aur both before and since 1980 indicate that the variable is undergoing an overall period increase, amounting to +0.082 +-0.012 s/yr, rather than a period decrease, as implied by all observations prior to 1980. Superposed on the star's O-C variations is a sinusoidal trend that cannot be attributed to random fluctuations in pulsation period. Rather, it appears to arise from light travel time effects in a binary system. The derived orbital period for the system is P = 26,429 +-89 days (72.36 +-0.24 years). The inferred orbital parameters from the O-C residuals differ from those indicated by existing radial velocity data. The latter imply the most reasonable results, namely a1 sin i = 9.09 (+-1.81) x 10^8 km and a minimum secondary mass of M2 = 1.15 +-0.25 Msun. Continued monitoring of the brightness and radial velocity changes in the Cepheid are necessary to confirm the long-term trend and to provide data for a proper spectroscopic solution to the orbit.Comment: Accepted for publication in PASP (November 2007

Twist txtrusion — technique for the structure formation

We present a study of the kinematics of Twist Extrusion (TE) and show that the mode of deformation in ТЕ is a simple shear. Unlike in Equal-Channel Angular Pressing (ECAP), there are two main shear layers perpendicular to the specimen axis. TE has a significant commercial potential due to the following physical effects: intensive grain refinement; homogenization and mixing; intensive powders consolidation. Donetsk Institute for Physics and Engineering created a TE Center to showcase the process and educate investors. Our experience with the center has shown that the most prospective directions are producing ultrafine-grained (UFG) alloys for medical and aircraft applications

Twist Extrusion: Fundamentals and Applications

The results of researches connected with both fundamental and applied aspects of Twist Extrusion (TE) are presented. It is shown: • TE combines advantages of HPT (implements the torsion scheme under pressure) and ECAP (allows you to receive the bulk samples) • TE leads to intense vortex motion of the material. Such an effect is absent in the ECAP. The main features of the TE are: formation multiscale vortex structure; intensive grain refinement; homogenization & mixing; intensive рowders consolidation. The recent results of TE from the point of view of its commercial potential are reported. It is shown TE is very promising for obtaining UFG materials, both via metals’ grain refinement and via powder consolidation. Twist Extrusion Center to showcase the process and educate investors was presented

EVIDENCES OF SURFACE DIFFERENTIAL ROTATION ON THE RED DWARF PZ MON

Photometric behavior of the active red dwarf PZ Mori (K2e) is studied using UBVRI obser­vations obtained with 1.25 m telescope of the SRI "Crimean Astrophysical Observatory" in 1992-2004 and V-data from the ASAS catalogue obtained in 2000­2006. Frequency analysis of the full V-data and colors has shown the existence of close periods – 2429d and 2500 d, respectively. Supposing that the star's surface is covered by spots a long-term variability can be ex­plained as changes of stellar activity during 6.5 years. After subtraction of slow periodicity some periods in the range of 15 d  - 56 d with amplitudes more than 4a were found. Period P = 34d found as at the whole in­terval of observations as at the short selected intervals is likely close to the rotation period of the star. Steady-phase of this period indicates the existence of an active longitude where spots are generated.

THE PRECESSION OF ASTEROID 1620 GEOGRAPHOS

The frequency analysis of the fine photometric effects in the photometric observation obtained during asteroid 1620 Geographos approaching to Earth in 1994 allowed to derive the precession of asteroid spin axis. The periods of 0d.8 and 2d.8 or multiple to them were revealed. The magnitude of precession angle was estimated to be near 3°. The nature of the precession discussed. The emergence of the free precession may be supported at time of the formation of the asteroid or by the collision with another body. The forced precession does not contradict to the Geographos connection with meteor streams and the assumption that Geographos may have small satellites