Herschel PACS and SPIRE imaging of CW Leonis

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)/√{n_ISM} km s^-1, where n_ISM is the number density of the local ISM.

Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.