TITLE: GCN GRB OBSERVATION REPORT NUMBER: 580 SUBJECT: GRB000301C 250 GHz detection DATE: 00/03/04 13:50:36 GMT FROM: Frank Bertoldi at MPIFR/Bonn Frank Bertoldi (MPIfR Bonn) reports: The likely afterglow of GRB 000301C (Smith et al., GCN 568) was detected at 250 GHz (1.2 mm) with the 37 channel Max-Planck Millimeter Bolometer (MAMBO) array (80 GHz bandwidth, 10.7 arcsec HPBW) at the IRAM 30 m telescope on Pico Veleta, at the position reported by Fynbo et al. (GCN 570) and Halpern et al. (GCN 578). The object was observed on 4 March 2000 from UTC 7 to 11:30, in standard on-off mode, under good weather conditions (stable atmosphere with opacity slowly rising from 0.21 to 0.26), and good pointing accuracy (<2"). The total on plus off target integration time was 7800 seconds. A source is clearly detected with flux density f(250 GHz) = 1.9 +- 0.3 mJy We hope to continue monitoring its flux.