BLACK-HOLE SOLUTIONS IN 2+1-DIMENSIONS

We give circularly symmetric solutions for null fluid collapse in (2+1 )-dimensional Einstein gravity with a cosmological constant. The fluid pressure P and energy density rho are related by P = k rho (k less th an or equal to 1). The long time limit of the solutions is a black hob whose horizon structure depends on the value of k. The k = 1 solution is the Banados-Teitelboim-Zanelli black hole metric in the long time static limit, while the k < 1 solutions give other, ''hairy,'' black h ole metrics in this limit.