New insights on the complex planetary nebula Hen 2-113

¹ Observatoire de la Côte d'Azur-CNRS-UMR 6202, Dept. Cassiopée, BP 4229, 06304 Nice, France e-mail: lagadec@obs-nice.fr
² Observatoire de la Côte d'Azur-CNRS-UMR 6203, Dept. Gemini, Avenue Copernic, 06130 Grasse, France
³ Department of Physics and Astronomy, University of Manchester, Sackville Street, PO Box 88, Manchester M60 1QD, UK
⁴ American Museum of Natural History, Dept. of Astrophysics, Central Park West at 79th Street, New York NY 10024, USA
⁵ Observatoire de Strasbourg, 11 rue de l'Université, 67000 Strasbourg, France
⁶ Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803, USA

Received: 8 July 2005
Accepted: 22 August 2005

Abstract

We report on infrared observations of the planetary nebula Hen 2-113 obtained with VLT/NACO, VLTI/MIDI, VLT/ISAAC and TIMMI at the ESO 3.6 m. Hen 2-113 exhibits a clear ring-like structure superimposed to a more diffuse environment visible in the L' (3.8 μm), M' (4.78 μm) and 8.7 μm bands. No clear core at 8.7 μm and no fringes through the N band could be detected for this object with MIDI. A qualitative interpretation of the object structure is proposed using a diabolo-like geometrical model. The PAH content of the nebula was also studied with ISAAC and TIMMI observations. This indicates that the PAHs are mostly concentrated towards the lobes of the diabolo and the bipolar lobes of the nebula. In L' band, a void in diameter was discovered with NACO around the central source. The L' and M' fluxes from the central source were derived from NACO data indicating an important infrared excess with respect to the expected stellar emission based on stellar models and short wavelength data. The observed flux from this source in the L' and M' is about 300 and 800 times respectively than those expected from a model including only the central star. Moreover, the central object appears resolved in L' band with measured FWHM of 155 mas. This infrared excess can be explained by emission from a cocoon of hot dust ( K) with a total mass ~.