Properties of OH, SIO, and H2O maser emission in O-rich AGB stars

Abstract

We investigate the properties of OH, SiO, and H2O maser emission in O-rich AGB stars. We use a sample of 3373 objects, which is an updated version of the list of O-rich AGB stars presented in Suh & Kwon (2011). We divide the 3373 O-rich AGB stars into four groups based on the maser emission: OH maser sources (1533), SiO sources (1627), H2O sources (452), and sources with no maser (610). To understand the nature of the maser sources, we present various infrared two-color diagrams (2CDs) using IRAS, 2MASS, and AKARI data. For each group, we compare the positions on various infrared 2CDs with theoretical models. We -nd that the OH maser sources generally show larger color indices and larger dust optical depths than SiO or H2O sources. We suggest that the of the color indices for maser sources are due to mass-loss rates and dust formation processes. © 2012 The Korean Astronomical Society. All Rights Reserved.