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Fermi can measure the spectral properties of gamma-ray bursts over a verylarge energy range and is opening a new window on the prompt emission of theseenergetic events. Localizations by the instruments on Fermi in combination withfollow-up by Swift provide accurate positions for observations at longerwavelengths leading to the determination of redshifts, the true energy budget,host galaxy properties and facilitate comparison with pre-Fermi bursts.Multi-wavelength follow-up observations were performed on the afterglows offour bursts with high energy emission detected by Fermi/LAT : GRB090323,GRB090328, GRB090510 and GRB090902B. They were obtained in theoptical/near-infrared bands with GROND mounted at the MPG/ESO 2.2m telescopeand additionally of GRB090323 in the optical with the 2 m telescope inTautenburg, Germany. Three of the events are classified as long bursts whileGRB090510 is a well localized short GRB with GeV emission. In addition, hostgalaxies were detected for three of the four bursts. Spectroscopic follow-upwas initiated with the VLT for GRB090328 and GRB090510. The afterglowobservations in 7 bands are presented for all bursts and their host galaxiesare investigated. Knowledge of the distance and the local dust extinctionenables comparison of the afterglows of LAT-detected GRBs with the generalsample. The spectroscopic redshifts of GRB090328 and GRB090510 were determinedto be z=0.7354+/-0.0003 and z=0.903 +/- 0.001 and dust corrected star-formationrates of 4.8 Mdot yr^-1 and 0.60 M_dot yr^-1 were derived for their hostgalaxies, respectively. The afterglows of long bursts exhibit power-law decayindices alpha from less than 1 to ~2.3 and spectral indices (beta) values from0.65 to ~1.2 which are fairly standard for GRB afterglows. Constraints areplaced on the jet half opening angles of less than 2.1 deg to greater than 6.4deg which allows limits to be placed on the beaming corrected energies. Theserange from less than 5x10^50 erg to the one of the highest values everrecorded, greater than 2.2x10^52 erg for GRB090902B, and are not consistentwith a standard candle. The extremely energetic long Fermi bursts have opticalafterglows which lie in the top half of the brightness distribution of alloptical afterglows detected in the Swift era or even in the top 5% ifincompleteness is considered. The properties of the host galaxies of these LATdetected bursts in terms of extinction, star formation rates and masses do notappear to differ from previous samples.

Optical and near-infrared follow-up observations of four Fermi/LAT GRBs : Redshifts, afterglows, energetics and host galaxies