The effectiveness of direct trade between China and near-border subjects of the Russian Federation

The subject matter of this article is the mutual international settlements between Russia (i.e. its border regions) and China in yuans. An advantage of such settlements is determined by the amount of money which can be spared by the Russian importers of Chinese products in case of direct trade. The topic of the article encompasses the analysis of export-import operations and national currencies’ use, in particular, the yuan, in the cross-border settlements between Russia and China. The objective of this article is to reveal the role of China in the international activities of the Russian near-border regions on the basis of the analysis of export and import statistics database. The hypothesis of this article is that the dynamics of Chinese imports to the Russian near-border regions correlates with the amount of the yuans traded on the Moscow Stock Exchange. The article produces forecasts of Chinese imports to the Russian near-border regions and the amount of money, which can be spared by the Russian importers in the case of a transition in bilateral settlements to the yuan. The outcomes of the article include the calculated indicators of the efficiency of the direct trade between China and Russia and of the coverage of Chinese imports in the Russian near-border regions by the yuan. The findings of the article are recommended to the Russian international companies as and reference point to increase the profitability of export-import operations with China, and to federal and local governments to create the Russian external economic strategy. The authors come to the conclusion that if the Chinese imports to the Russian border region were in the yuan, then the yuans volume of trade on the Russian foreign exchange market would allow the direct settlements with China

A 450-day light curve of the radio afterglow of GRB 970508: Fireball calorimetry

We report on the results of an extensive monitoring campaign of the radio afterglow of GRB 970508, lasting 450 days after the burst. The spectral and temporal radio behavior indicate that the fireball has undergone a transition to sub-relativistic expansion at t~100 days. This allows us to perform "calorimetry" of the explosion. The derived total energy, ~5\times 10^{50} erg, is well below the ~5\times 10^{51} erg inferred under the assumption of spherical symmetry from gamma-ray and early afterglow observations. A natural consequence of this result, which can also account for deviations at t<100 days from the spherical relativistic fireball model predictions, is that the fireball was initially a wide-angle jet of opening angle ~30 degrees. Our analysis also allows to determine the energy fractions carried by electrons and magnetic field, and the density of ambient medium surrounding the fireball. We find that during the sub-relativistic expansion electrons and magnetic field are close to equipartition, and that the density of the ambient medium is ~1/cm^3. The inferred density rules out the possibility that the fireball expands into a strongly non-uniform medium, as would be expected, e.g., in the case of a massive star progenitor.Comment: 33 pages, including 7 figures, submitted to Ap

The Afterglow of GRB 990123 and a Dense Medium

Recent observations show that the temporal decay of the R-band afterglow from GRB 990123 steepened about 2.5 days after the burst. We here propose a possible explanation for such a steepening: a shock expanding in a dense medium has undergone the transition from a relativistic phase to a nonrelativistic phase. We find that this model is consistent with the observations if the medium density is about $3\times 10^6 {\rm cm}^{-3}$. By fitting our model to the observed optical and X-ray afterglow quantitatively, we further infer the electron and magnetic energy fractions of the shocked medium and find these two parameters are about 0.1 and $2\times 10^{-8}$ respectively. The former parameter is near the equipartition value while the latter is about six orders of magnitude smaller than inferred from the GRB 970508 afterglow. We also discuss possibilities that the dense medium can be produced.Comment: 12 pages, LaTeX, published in ApJ Letter

Time-dependent spectral-feature variations of stars displaying the B[e] phenomenon III. HD 50138

We analyse spectroscopic observations of the B[e] star HD 50138 (MWC 158, V743 Mon, or IRAS 06491-0654), a member of the FS CMa group, obtained over the last twenty years. Four different epochs are identified in the observational data, where the variability of the spectral features is substantially different. Additionally, two long periods of (3 000 +/- 500) and (5 000 +/- 1000) days are found in the variations of the equivalent widths of the H alpha and [OI] 6300 A lines and radial velocities of the H alpha line violet peak. Modest signatures of a regular period of ~34 days in the radial velocities of the H alpha red peak and H beta central depression are found in the season 2013/2014. The H alpha V/R changes indicate a periodicity of ~50 days. The correlations between individual spectral features significantly restricts the model of the object and suggest that it is most likely a binary system with a highly distorted disc with spiral arms around the primary component. At the same time, no obvious signs of the secondary component has been found in the object's spectrum

Environment and Energy Injection Effects in GRB Afterglows

In a recent paper (Dai & Lu 1999), we have proposed a simple model in which the steepening in the light curve of the R-band afterglow of the gamma-ray burst (GRB) 990123 is caused by the adiabatic shock which has evolved from an ultrarelativistic phase to a nonrelativistic phase in a dense medium. We find that such a model is quite consistent with observations if the medium density is about $3\times 10^6 {\rm cm}^{-3}$. Here we discuss this model in more details. In particular, we investigate the effects of synchrotron self absorption and energy injection. A shock in a dense medium becomes nonrelativistic rapidly after a short relativistic phase. The afterglow from the shock at the nonrelativistic stage decays more rapidly than at the relativistic stage. Since some models for GRB energy sources predict that a strongly magnetic millisecond pulsar may be born during the formation of GRB, we discuss the effect of such a pulsar on the evolution of the nonrelativistic shock through magnetic dipole radiation. We find that after the energy which the shock obtains from the pulsar is much more than the initial energy of the shock, the afterglow decay will flatten significantly. When the pulsar energy input effect disappears, the decay will steepen again. These features are in excellent agreement with the afterglows of GRB 980519, GRB 990510 and GRB 980326. Furthermore, our model fits very well all the observational data of GRB 980519 including the last two detections.Comment: 21 pages, LaTeX, accepted for publication in ApJ, one paragraph adde