The oxygen abundance gradient in M 101: The reliability of the P method

We present the oxygen abundance determination for 90 HII regions in the inner parts of the grand design galaxy M 101. The abundances were derived employing the P method (Pilyugin [CITE]). A comparison is made with previous determinations using another calibration and direct measurements of electron temperature to derive the oxygen abundance. The results show agreement with the abundances derived from the electron temperature method and also show that the older calibration is not as accurate as the P method.