TITLE: GCN GRB OBSERVATION REPORT NUMBER: 991 SUBJECT: GRB010222: R-band data DATE: 01/02/26 00:30:59 GMT FROM: Krzysztof Z. Stanek at CfA K. Z. Stanek and E. Falco (Harvard-Smithsonian CfA) report: We have obtained additional R-band data for the optical afterglow of the GRB010222 using the F. L. Whipple Observatory 1.2m telescope: UT R_c exp 25.4385 21.48+-0.08 2x600 sec Fitting a simple power-law decay to our data taken about one day after the burst (GCN 983) and the current data yields a slope of about 1.3. This confirms the steepening decay of the optical afterglow, as indicated by Masetti et al. (GCN 985). Fitting broken power-law to all the data produces a food fit, but the parameters of the fit are at present underconstrained, except that the break seems to be gradual, beta<<1. Continuing imaging is needed, also in the BVI-bands if possible. The R-band magnitude is relative to star "A" as marked in the finding chart at http://cfa-www.harvard.edu/cfa/oir/Research/GRB/, assuming its magnitude R=17.0. Because of the discrepancy between the values assigned to "A" by Valentini et al. (GCN 986: R=16.7) and Henden (GCN 987: R=17.175), we decided for now to continue using R=17.0 as our fiducial point. This message can be cited.