TITLE: GCN GRB OBSERVATION REPORT NUMBER: 1209 SUBJECT: GRB 011211, spectrum and optical photometry DATE: 01/12/18 18:32:08 GMT FROM: Peter Garnavich at U of Notre Dame M. Gladders (OCIW), S. Holland, P. M. Garnavich (Notre Dame), S. Jha, K. Z. Stanek, D. Bersier (CfA), L. F. Barrientos (U. Catolica) Spectra of the candidate afterglow of GRB 011211 (Grav et al. GCN 1191) were obtained with the Magellan 6.5m Walter Baade telescope and LDSS-2 imaging spectrograph on 2001, Dec. 13.3 (UT). The spectra cover the range 400 nm to 900 nm at a resolution of 1.2 nm (FWHM). Four exposures, each with an exposure time of 620s, were fully reduced and combined. The final spectrum shows a smooth continuum except for a number of narrow absorption lines in the blue. Observed ID z -------- --------- ---- 524.8 nm Al II (167.1) 2.141 486.5 C IV (154.9) 2.141 479.4 Si II (152.7) 2.140 439.3 Si IV (139.8) 2.142 409.1 O I/Si II (130.3) 2.140 A broad, unidentified feature is seen at 460.0 nm (146.5 nm rest frame). These identifications confirm the redshift of z=2.14 found by Fruchter et al. (GCN 1200). R-band images were also obtained in imaging mode on Dec. 12 and 13 (UT). Assuming R=17.76 U0675_11427359 given by Henden (2001, GCN 1197) we find the following magnitudes for the probable afterglow: Dec. 12.25 20.28 +/-0.02 Dec. 12.34 20.58 +/-0.02 Dec. 13.31 21.46 +/-0.04 which provide a power law index of 0.9, consistent with the optical decline rates found by Soszynski et al. (GCN 1199) for the same time interval. The fits images and spectra are available at http://www.astro.utoronto.ca/~gladders/GRB/ This message may be cited.