TITLE: GCN GRB OBSERVATION REPORT NUMBER: 1152 SUBJECT: GRB011121: possible redshift, continued decay DATE: 01/11/22 12:10:45 GMT FROM: Krzysztof Z. Stanek at CfA L. Infante (Pontificia Univ. Catolica de Chile), P. M. Garnavich (Notre Dame), K. Z. Stanek (Harvard-Smithsonian CfA) and Lukasz Wyrzykowski (Warsaw University Observatory) report: Spectra of the possible OT (Wyrzykowski et al.: GCN 1150) obtained with the Magellan Walter Baade 6.5m telescope and the LDSS-2 spectrograph on Nov. 22.3 (UT) show a smooth continuum with a peak flux near 650 nm. Narrow emission lines, likely from the host galaxy, are seen at 507.58 nm and 681.0 nm, which may correspond to [O II] 372.7 and [O III] 500.7 nm at a redshift of 0.36. The depressed blue end of the spectrum is most likely due to strong Galactic dust extinction. Also, additional R-band observation of the GRB011121 field carried out with the OGLE 1.3m telescope 13.75 hours after the burst indicates continuing fading behavior of the afterglow, as seen already by Stanek et al. (GCN 1151): HJD-2450000 UT R_c exp 2235.85176 011122 08:30 18.80+-0.03 600 sec This behavior is consistent with a power-law decay with an index of -1.65. The R-band magnitudes are relative to star "A" of Wyrzykowski et al. (see finding chart at http://cfa-www.harvard.edu/cfa/oir/Research/GRB/). The faint object 0.5" to the northeast of the OT reported by Stanek et al. is easily visible in 600 sec R-band exposure. Relatively low redshift and fast decay of its afterglow make GRB011121 an attractive search target for a possible supernova associated with this burst. This message can be cited.