TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3561 SUBJECT: GRB 050408: ARC 3.5-meter NIR Observations DATE: 05/07/02 15:17:43 GMT FROM: Don Lamb at U.Chicago GRB 050408: ARC 3.5-meter NIR Observations J. Flasher (Colorado), F. Hearty (Colorado), G. Stringfellow (Colorado), J. Walawender (Colorado), D. Q. Lamb (Chicago), T. Lisker (Washington), V. Debattista (Washington), J. Dembicky (APO), J. Barentine (APO), R. McMillan (APO), B. Ketzeback (APO), and D. G. York (Chicago) report on behalf of the ARC GRB team of the FUN GRB collaboration: We observed the afterglow (Wells et al., GCN Circular No. 3191; Postigo et al., GCN Circular No. 3192) of GRB 050408, a burst localized by HETE-2 (Sakamoto et al., GCN Circular No. 3189), on the night of April 8th, using NIC-FPS on the ARC 3.5-meter telescope at Apache Point Observatory. The observation began at 04.47 UT (12.29 hours after the burst) and ended at 07.06 UT (14.68 hours after the burst). The observation consisted of a series of 120-, 120-, 20-, and 20-second exposures in Z, J, H, and Ks, respectively. We have constructed stacked images of the GRB field, corresponding to 20-minute exposures in each filter. We detect the afterglow in all four filters, and measure Z = 21.8 ± 0.12, calibrated relative to the SDSS stars in the field. NIC-FPS is currently in its commissioning phase. This message may be cited.