6,907 research outputs found
Evolutionary constraints on the masses of the components of HDE 226868/Cyg X-1 binary system
Calculations carried out to model the evolution of HDE 226868, under
different assumptions about the stellar wind mass loss rate, provide robust
limits on the present mass of the star. It has to be in the range 40 +- 5 solar
masses if the distance to the system is in the range 1.95 to 2.35 kpc and the
effective temperature of HDE 226868 in the range 30000 to 31000 K. Extending
the possible intervals of these parameters to 1.8 to 2.35 kpc and 28000 to
32000 K, one gets for the mass of the star the range 40 +- 10 solar masses.
Including into the analysis observational properties such as the profiles of
the emission lines, rotational broadening of the absorption lines and the
ellipsoidal light variations, one can estimate also the mass of the compact
component. It has to be in the ranges 20 +- 5 solar masses and 13.5 to 29 solar
masses for the cases described above. The same analysis (using the evolutionary
models and the observational properties listed above) yields lower limit to the
distance to the system of about 2.0 kpc, if the effective temperature of HDE
226868 is higher than 30000 K. This limit to the distance does not depend on
any photometric or astrometric considerations.Comment: 11 pages, 4 figures, accepted for publication in MNRA
A candidate for the parent body of the Taurid complex and its search ephemeris
Untypical asteroid 5025 P-L, with its perihelion close to the orbit of Mercury and its aphelion between the orbits of Jupiter and Saturn, seems to be a good candidate for the parent body of the Taurid complex of small interplanetary objects. Evidence that this asteroid is a major source of meteoroids as well as an analysis of the orbits of asteroidal and cometary members of the Taurid complex, lead to the conclusion that 5025 P-L might be regarded as a remnant of a giant comet which was a progenitor of the overall complex according to the hypothesis of Clube and Napier. Unfortunately, the orbit of 5025 P-L is very poorly determined because the computations were based upon only three positional observations over an arc of only four days in October 1960. Any further research on the problem of origin and evolution of the Taurid complex needs better determined orbit of this key asteroid. Therefore its new positions are necessary. In order to enable the search of eventual trails of 5025 P-L on plates which can be found in archives, its ephemeris for the opposition in 1960, when the asteroid passed about 0.5 AU from the Earth, is presented
Excitation of guided waves in layered structures with negative refraction
We study the electromagnetic beam reflection from layered structures that
include the so-called double-negative materials, also called left-handed
metamaterials. We predict that such structures can demonstrate a giant lateral
Goos-Hanchen shift of the scattered beam accompanied by splitting of the
reflected and transmitted beams due to the resonant excitation of surface waves
at the interfaces between the conventional and double-negative materials as
well as due to excitation of leaky modes in the layered structures. The beam
shift can be either positive or negative, depending on the type of the guided
waves excited by the incoming beam. We also perform finite-difference
time-domain simulations and confirm the major effects predicted analytically.Comment: 13 pqages, 10 figures. Also available at
http://www.opticsexpress.org/abstract.cfm?URI=OPEX-13-2-48
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