8,014 research outputs found
Tidal interaction of a rotating 1 Msun star with a binary companion
We calculate the tidal torque on a uniformly rotating 1 Msun star at various
stages of core hydrogen burning by an orbiting companion. We apply the
`traditional approximation' and solve the radial part of the tidal
perturbations by matrix inversion of the set of finite difference equations on
a very fine grid. We have identified resonances with gravity- and
quasi-toroidal modes with up to 1000 radial nodes in the more evolved stellar
models. For low forcing frequencies we find significant tidal response due to
viscous damping of inertial modes in the convective envelope of the solar-type
star. We conclude that effects due to stellar rotation (including resonance
locking) may considerably enhance the speed of tidal evolution in solar-type
stars.Comment: accepted for publ. in A&A, 11 pages, 6 figure
Tidal evolution of eccentric orbits in massive binary systems; a study of resonance locking
We study the tidal evolution of a binary system consisting of a 1.4 Msun
compact object in elliptic orbit about a 10 Msun uniformly rotating main
sequence star for various values of the initial orbital parameters. We apply
our previously published results of 2D non-adiabatic calculations of the
non-radial g- and r-mode oscillations of the uniformly rotating MS star, and
include the effects of resonant excitation of these modes in the tidal
evolution calculations. A high orbital eccentricity enhances the effectiveness
of the tidal interaction because of the large number of harmonic components of
the tidal potential and the reduced orbital separation near periastron. By
including the evolution of the MS star, especially of its rotation rate, many
resonance crossings occur with enhanced tidal interaction. We analyse the
phenomenon of resonance locking whereby a particular tidal harmonic is kept
resonant with a stellar oscillation mode. Resonance locking of prograde g-modes
appears an effective mechanism for orbital circularization of eccentric orbits.
We consider the orbital evolution of the binary pulsar PSR J0045-7319 and
conclude that resonance locking could explain the observed short orbital decay
time of this system if the B-star spins in the direction counter to the orbital
motion.Comment: 21 pages, 11 figures; some at reduced resolution, accepted for
publication in A&
The use of ERTS-1 to more fully utilize and apply marine station data to the study and productivity along the eastern shelf waters of the United States
The author has identified the following significant results. Sea truth data were obtained during two ERTS overpasses in waters near the entrance of the Chesapeake Bay. Correlations were made between total phytoplankton and chlorophyll values in these waters to radiance detected by ERTS in an effort to map areas of similar productivity levels. Band 4 radiance had the highest correlation to all parameters with bands 5 and 6 showing decreasing correlations in each case. The radiance values were apparently influenced by one or more factors, most likely including the sediment content of the water. Data have shown that ERTS MSS is not suitable for monitoring chlorophyll in near-shore waters where sediment loads are high. It is suggested that in more seaward or pelagic locations, that ERTS MSS would be more efficient in monitoring surface chlorophyll values and establishing direct relationships to phytoplankton concentrations
Heat transfer characteristics of an emergent strand
A mathematical model was developed to describe the heat transfer characteristics of a hot strand emerging into a surrounding coolant. A stable strand of constant efflux velocity is analyzed, with a constant (average) heat transfer coefficient on the sides and leading surface of the strand. After developing a suitable governing equation to provide an adequate description of the physical system, the dimensionless governing equation is solved with Laplace transform methods. The solution yields the temperature within the strand as a function of axial distance and time. Generalized results for a wide range of parameters are presented, and the relationship of the results and experimental observations is discussed
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