The extreme Type I planetary nebula M2-52

Abstract

High-resolution spectrophotometric data of the central zone of the Br-type planetary nebula M2-52 are presented. The nebula has a rich spectrum, with high and low excitation lines. The chemical composition derived from the spectra shows that He and N are very enhanced in M2-52. Thus, this object can be classified as an extreme Peimbert's Type I PN. The chemical composition of the ionized gas is: He/H =0.165 +/- 0.010, O/H = (2.6 +/- 0.5)E-04, N/O = 2.3 +/- 0.3, Ne/O = 0.37 +/-0.10, Ar/O = (9.2 +/- 2.0)E-03 and S/O > 2.0 E-03. The expansion velocity of the nebula is, on average, about 20 +/- 2 km/s, but the low ionization species (N+ and S+) seem to show systematically slightly lower expansion velocities (18 km/s) than O(++) and He+ which have v(exp) = 20 km/s while H+ and He(++) present v(exp) = 22 km/s. This behavior could indicate that the outer zones of the ionized gas are being decelerated by the molecular ring located around the central star.