Since 1997, and following our detection of the first mm afterglow, we have followed-up 70
GRBs, mainly with the IRAMś Plateau de Bure Interferometer, what can be considered as the
IRAM Legacy GRB Sample. 66 events were observed at 3 mm, with 19 of them being detected
(with another 3 having marginal detections). 32 GRBs were followed up at 1 mm, with 6 of
them being detected. Redshifts for the GRB afterglows lie in the range z = 0.03–8.3, with
measured flux densities (at 3 mm) varying between 0.25 and 60 mJy (but usually <1.5
mJy) with first observations taking place around 1–2 days after the GRB. Forward shock
emission expleains the observations with the exception of one particular case (GRB 090423
at z = 8.2) for which reverse shock emission is required.