Letter to the Editor

The detection of iron sulfides in Planetary Nebulae^*

¹ Astronomical Institute “Anton Pannekoek”, University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
² CEA, DSM, DAPNIA, Service d'Astrophysique, CEN Saclay, 91191 Gif-sur-Yvette Cedex, France
³ Mail Code SR, NASA Johnson Space Center, Houston, Texas 77058, USA
⁴ Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200B, 3001 Heverlee, Belgium

Corresponding author: S. Hony, hony@astro.uva.nl

Received: 9 July 2002
Accepted: 29 August 2002

Abstract

We present and discuss the detection, through mid IR spectroscopy, of iron sulfides in the carbon rich ejecta of evolved stars. We find the spectroscopic signature of iron sulfides at 23 μm. We also find weak features at ~34, 38 and 44 μm. The positions of these features correspond well with the resonances of the iron sulfide troilite. However, the relative strength of the 23 μm versus the other bands does not match the laboratory measurements, which suggests the presence of other iron sulfides besides troilite. The same broad feature around 23 μm has been found in young stellar objects. This detection may imply a carbon star origin for part of the iron sulfides found in meteorites and interplanetary dust particles.