Letter to the Editor

Herschel PACS and SPIRE imaging of CW Leonis^*

¹ Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium e-mail: Djazia.Ladjal@ster.kuleuven.be
² Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
³ Koninklijke Sterrenwacht van België, Ringlaan 3, 1180 Brussels, Belgium
⁴ Dept. of Physics and Astronomy, University of Denver, Mail Stop 6900, Denver, CO 80208, USA
⁵ Radio Astronomy Laboratory, University of California at Berkeley, CA 94720, USA
⁶ Sterrenkundig Instituut Anton Pannekoek, Universiteit van Amsterdam, Kruislaan 403, 1098 Amsterdam, The Netherlands
⁷ School of Physics and Astronomy, Cardiff University, 5 The Parade, Cardiff, Wales CF24 3YB, UK
⁸ UK Astronomy Technology Centre, Royal Observatory Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK
⁹ University Vienna, Department of Astronomy, Türkenschanzstrasse 17, 1180 Wien, Austria
¹⁰ Space Science and Technology Department, Rutherford Appleton Laboratory, Oxfordshire, OX11 0QX, UK
¹¹ Dept. of Astronomy, Stockholm University, AlbaNova University Center, Roslagstullsbacken 21, 10691 Stockholm, Sweden
¹² Department of Physics, University of Lethbridge, Alberta, Canada

Received: 31 March 2010
Accepted: 15 April 2010

Abstract

Herschel PACS and SPIRE images have been obtained over a 30' × 30' area around the well-known carbon star CW Leo (IRC +10 216). An extended structure is found in an incomplete arc of ~22' diameter, which is cospatial with the termination shock due to interaction with the interstellar medium (ISM) as defined by Sahai & Chronopoulos from ultraviolet GALEX images. Fluxes are derived in the 70, 160, 250, 350, and 550 μm bands in the region where the interaction with the ISM takes place, and this can be fitted with a modified black body with a temperature of 25 ± 3 K. Using the published proper motion and radial velocity for the star, we derive a heliocentric space motion of 25.1 km s^-1. Using the PACS and SPIRE data and the analytical formula of the bow shock structure, we infer a de-projected standoff distance of the bow shock of R₀ = (8.0 ± 0.3) × 10¹⁷ cm. We also derive a relative velocity of the star with respect to the ISM of (106.6 ± 8.7)/ km s^-1, where n_ISM is the number density of the local ISM.