High resolution H band imaging polarimetry of IRC +10216

The obscured location of the central star

¹ Subaru Telescope, 650 North A'ohoku place, Hilo, HI 96720, USA e-mail: murakawa@naoj.org
² University College London, Gower street, London, WC1E 6BT, UK
³ Royal Observatory of Belgium, Ringlaan 3, 1180 Brusseles, Belgium
⁴ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21282, USA

Received: 30 August 2004
Accepted: 3 February 2005

Abstract

We have carried out an H band imaging polarimetry of an evolved AGB star IRC +10216 using CIAO and AO on the Subaru telescope. Our polarimetric images show NE-S bipolar lobes, a NW lobe, a discrete NW arc with ~ radius and two new features of a fan-like shape at the SE and of an elliptic shape at the NW with small polarizations () near the intensity peak. The polarization vectors in the NE-S lobes and the NW lobe have a centrosymmetric pattern centered at the position of the illumination source (the central star). The illumination source is located at (+025, -0065) from the intensity peak between the SE fan and the NW ellipse. The polarization vectors between these two features are aligned along a line across them. We interpret that the appearance of the SE fan and the NW ellipse reflects a sudden increase of the mass loss rate that likely initiated the formation of an edge-on dust torus. This sudden mass loss increase probably began about a half century ago.