Polarization observable measurements for γp → K +Λ and γp → K+∑0 for energies up to 1.5 GeV

Beam asymmetries and hyperon recoil polarizations for the reactions γp → K +Λ and γp → K +∑0 have been measured from the threshold production to 1500MeV with the GRAAL facility located at the ESRF in Grenoble. These results complement the database for the beam asymmetry, covering for the first time the production threshold region. Recent theoretical analyses are presented for which the beam asymmetry data bring interesting new information and allow to better determine some resonance parameters. Most importantly, these results strengthen the need of a new D13 state around 1900MeV.