D-brane Bound States from Charged Macroscopic Strings

We construct new D-brane bound states using charged macroscopic type IIB string solutions. A generic bound state solution, when dimensionally reduced, carries multiple gauge charges. Starting with D = 9 charged macroscopic strings, we obtain solutions in D = 10, which are interpreted as carrying (F , D0, D2) charges as well as nonzero momenta. The masses and charges are also explicitly shown to satisfy the non-threshold bound of 1/2 BPS objects. Our solutions reduce to the known D-brane bound state solutions with appropriate restrictions in the parameter space. We further generalize the results to (Dp − D(p + 2)) bound state in IIA/B theories, giving an explicit example with p = 1.