86 GHz SiO maser survey of late-type stars in the inner Galaxy

III. Interstellar extinction and colours of the SiO targets

¹ European Southern Observatory, Karl Schwarzschild-Strasse 2, 85748 Garching bei Munchen, Germany e-mail: mmessine@eso.org
² Leiden Observatory, PO Box 9513, 2300 RA Leiden, The Netherlands
³ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
⁴ Institut d'Astrophysique de Paris, CNRS & Université Paris 6, 98bis Bd Arago, 75014 Paris, France
⁵ National Radio Astronomy Observatory, PO Box 0, Socorro NM 87801, USA
⁶ Radioastronomisches Institut der Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany

Received: 26 March 2004
Accepted: 14 January 2005

Abstract

We have determined extinction corrections for a sample of 441 late-type stars in the inner Galaxy, which we previously searched for SiO maser emission, using the 2MASS near-infrared photometry of the surrounding stars. From this, the near-infrared extinction law is found to be approximated by a power law . Near- and mid-infrared colour–colour properties of known Mira stars are reviewed. From the distribution of the dereddened infrared colours of the SiO target stars we infer mass-loss rates between 10^-7 and  yr^-1.