On behalf of the Apache Point Observatory GRB team, A. Diercks & C. Stubbs observed with the APO 3.5m telescope the optical transient (OT) discovered by Jaunsen et al. (GCN #78) in the BeppoSAX error box of GRB 980519. Conditions were mostly cloudy with roughly 1.8 arcsec seeing. Photometry by E. Deutsch & A. Diercks on a 1 hr series of images centered around May 20.44 UT yields the following magnitudes and relative uncertainties for the OT and reference stars:
ID R mag RelErr -- ----- ----- OT 21.20 0.03 A 17.93 0.01 B 19.31 0.01 C 18.06 0.01Absolute calibration is based only on R magnitudes of reference stars reported by Kemp & Halpern (GCN #80). No independent calibration was possible due to heavy clouds. Our measurement for the OT is 0.3 mag fainter than the earlier observations of Kemp & Halpern (GCN #80).
Images are posted at: http://www.astro.washington.edu/deutsch/grb/grb980519/
This note can be cited.