POST-NEWTONIAN LIMITS AND GRAVITATIONAL-RADIATION FROM THE SUPERSTRING EFFECTIVE ACTION

We consider the gravitational sector of the superstring effective acti on with axion-matter couplings. The field equations are developed in t he post-Newtonian scheme and approximate solutions for a spinning poin t mass and a cosmic string are presented. Furthermore, assuming vanish ing axion mass and vanishing potential for the dilaton, we consider th e gravitational radiation in the leading O(alpha'0) order. We find tha t the total luminosity of a radiative source has monopole and dipole c omponents besides the standard quadrupole one. These components may po ssibly be checked in binary systems.