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Heavy element abundances in extremely metal-poor stars provide strongconstraints on the processes of forming these elements in the first stars. Weattempt to determine precise abundances of strontium in a homogeneous sample ofextremely metal-poor stars. The abundances of strontium in 54 very or extremelymetal-poor stars, was redetermined by abandoning the local thermodynamicequilibrium (LTE) hypothesis, and fitting non-LTE (NLTE) profiles to theobserved spectral lines. The corrected Sr abundances and previously obtainedNLTE Ba abundances are compared to the predictions of several hypotheticalformation processes for the lighter neutron-capture elements. Our NLTEabundances confirm the previously determined huge scatter of the strontiumabundance in low metallicity stars. This scatter is also found (and is evenlarger) at very low metallicities (i. e. early in the chemical evolution). TheSr abundance in the extremely metal-poor (EMP) stars is compatible with themain r-process involved in other processes (or by variations of the r-process),as we briefly discuss.

NLTE strontium abundance in a sample of extremely metal poor stars and the Sr/Ba ratio in the early Galaxy