9457460 Kumar The research to be carried out will be divided between studies of solar oscillations and a few other problems in astrophysics. Three specific projects are described below: The rotation profile in the solar interior was mapped by helioseismology several years ago, and yet our theoretical understanding of the physical processes taking place in the sun is very poor. However, progress has been made on this problem (Kumar, Narayan and Loeb), and the plan is to continue to work on this problem. The solution of this problem is not only important in the context of understanding stars, but has considerably wider application in astrophysics. A detailed study of the tidal evolution of binary stars, which includes the transfer of angular momentum and the tidal energy dissipation in stars, is being carried out. Particular emphasis will be placed on astrophysical binary systems containing a neutron star (pulsar) which allows very accurate determination of the orbital parameters, including the periastron advance. Two such binary systems, because of their high eccentricity and small periastron distance, are particularly interesting from the point of view of detecting tidally forced oscillations in the companion main sequence star. A number of pressure and gravity modes of oscillations are expected to be tidally excited in these stars to an observable amplitude. The detection of these oscillations will enable us to determine both the mass and the age of the stars very accurately. This should provide an excellent opportunity for studying the orbital evolution of the binary orbits. The last project that will be pursued pertains to the study of the large velocity dispersion of the material in molecular clouds. There are several giant molecular clouds about 1 kiloparsec in distance from the galactic center which are very peculiar in that they show a large random internal velocity. The velocity dispersion of the clouds, obtained by observing the carbon m onoxide (CO) emission, is found to be about four times their virial velocity. These observations are also supported by observations of other molecular emissions as well as by the 21 cm neutral hydrogen line emissions from the clouds. Therefore, it is almost certain that these clouds are not gravitationally bound. A plausible model for the large velocity dispersion is clumping and collisions of clouds that are moving on non-circular orbits in a bar potential. This theoretical model will be analyzed carefully to see whether it explains the observations. The observations of the clouds may offer additional evidence for the presence of a bar in the central region of our Galaxy. This award is to recognize an outstanding young faculty member in science and engineering. The award will enhance the career of the faculty member by providing flexible support for research and educational activities. Cooperation with industry and institutions that support research and education is encouraged.
