TITLE: GCN GRB OBSERVATION REPORT NUMBER: 181 SUBJECT: GRB 981226 optical observations DATE: 98/12/30 05:52:14 GMT FROM: James Rhoads at KPNO James Rhoads (KPNO), Jerome A. Orosz (Penn State University), John Lee (Yale University), and Keivan Stassun (U Wisconsin); report on behalf of the KPNO GRB followup team: We have observed the field of GRB 981226 on 1998 December 27.156 (J. Lee observing), 28.100 (J. Lee observing), and 29.096 (K. Stassun observing) using the 0.9m telescope and CCD Mosaic Camera at Kitt Peak National Observatory. Total integration times were 24, 24, and 40 minutes on the three nights. Intermittent cloud on the first night resulted in a comparatively shallow image, with limiting magnitude R ~ 20.5. Limiting magnitudes on the 2nd and 3rd nights were R ~ 21. (These are very approximate estimates based on the USNO-A catalog magnitude R=16.9 for the star at 23:29:29.3 -23:57:36 [J2000].) The full field of view is 1 degree, and so covers the entire BeppoSAX WFC error region and more. Sections of the reduced images are available in FITS format at http://www.noao.edu/noao/grb/981226.html together with further details. Preliminary analysis yields no new sources clearly above the detection limits for the POSS plates, and no convincingly variable sources. We do not detect any object at the position of the J band transient reported by Castro-Tirado et al. The source reported by Galama et al (GCNC 172) is apparent in all of our images and does not appear to vary more than 20%; tighter limits will require deeper images. In addition, J. Orosz observed the field on the same three nights using the KPNO 2.1m telescope with R band (Dec 27, 28 UT) and I band (Dec 29 UT) filters. The data cover part of the original BeppoSAX WFC error box. These data are also available from the same web site. Further analysis of both data sets is underway. This report is citable.