Bounds on very low reheating scenarios after Planck

We consider the case of very low reheating scenarios Tₑ₇ (MeV) with a better calculation of the production of the relic neutrino background (with three-flavor oscillations). At 95% confidence level, a lower bound on the reheating temperature Tₑ₇>4. 1 MeV is obtained from big bang nucleosynthesis, while Tₑ₇>4. 7 MeV from Planck data (allowing neutrino masses to vary), the most stringent bound on the reheating temperature to date. Neutrino masses as large as 1 eV are possible for very low reheating temperatures.