Helioseismic determination of Beryllium neutrinos produced in the Sun
  We provide a determination of the Beryllium neutrino luminosity directly by means of helioseismology, without using additional assumptions. We have constructed solar models where Beryllium neutrino, ($\nu_{Be}$) production is artificially changed by varying in an arbitrary way the zero energy astrophysical S-factor $S_{34}$ for the reaction $^3{\rm He}+^4{\rm He}\to ^7{\rm Be}+ \gamma$.   Next we have compared the properties of such models with helioseismic determinations of photospheric helium abundance, depth of the convective zone and sound speed profile. We find that helioseismology directly confirms the production rate of $\nu_{Be}$ as predicted by SSMs to within $\pm 25%$ ($1\sigma$ error). This constraint is somehow weaker than that estimated from uncertainties of the SSM ($\pm 10%$), however it relies on direct observational data. 
B. Ricci and F.L. Villante