A YOUNG SUPER STAR CLUSTER IN THE NUCLEAR REGION OF NGC 253

We present observations of a massive star cluster near the nuclear region of the nearby starburst galaxy NGC 253. The peak of near-infrared (IR) emission, which is spatially separated by 4 '' from the kinematic center of the galaxy, is coincident with a super star cluster whose properties we examine with low-resolution (R similar to 1200) infrared Cerro Tololo Inter-American Observatory spectroscopy and optical/near-IR Hubble Space Telescope imaging. Extinction, measured from Fe II lines, is estimated at A(V) = 17.7 +/- 2.6. The age of the cluster is estimated at 5.7 Myr, based on Br gamma equivalent width for an instantaneous burst using Starburst99 modeling. However, a complex star formation history is inferred from the presence of both recombination emission and photospheric CO absorption. The ionizing photon flux has a lower limit of 7.3 +/- 2.5 x 10(53) s(-1), corrected for extinction. Assuming a Kroupa initial mass function, we estimate a cluster mass of similar to 1.4(-0.5)(+0.4) x 10(7) M(circle dot). We observe a strong Wolf-Rayet signature at 2.06 mu m and report a weak feature at 2.19 mu m which may be due to a massive stellar population, consistent with the derived mass and age of this cluster.