We have measured radial velocities and metallicities of 16 RR Lyrae stars , from the QUEST survey , in the Sagittarius tidal stream at 50 kpc from the galactic center .
The distribution of velocities is quite narrow ( \sigma = 25 km/s ) indicating that the structure is coherent also in velocity space .
The mean heliocentric velocity in this part of the stream is 32 km/s .
The mean metallicity of the RR Lyrae stars is [ Fe/H ] = -1.7 .
Both results are consistent with previous studies of red giant stars in this part of the stream .
The velocities also agree with a theoretical model of the disruption of the Sagittarius galaxy .