Research Note

Effects of moderate abundance changes on the atmospheric structure and colours of Mira variables

¹ Zentrum für Astronomie der Universität Heidelberg (ZAH), Institut für Theoretische Astrophysik, Albert-Ueberle-Str. 2, 69120 Heidelberg, Germany
e-mail: michael.scholz@uni-heidelberg.de
² Sydney Institute for Astronomy (SIfA), School of Physics, University of Sydney, Sydney NSW 2006, Australia
³ Department of Physics and Astronomy, Macquarie University, North Ryde, Sydney NSW 2109, Australia
⁴ Australian Astronomical Observatory, Epping, Sydney NSW 1710, Australia
e-mail: michael.ireland@anu.edu.au
⁵ Research School of Astronomy and Astrophysics, Australian National University, Canberra ACT 2600, Australia
e-mail: peter.wood@anu.edu.au

Received: 4 December 2013
Accepted: 24 April 2014

Abstract

Aims. We study the effects of moderate deviations from solar abundances upon the atmospheric structure and colours of typical Mira variables.

Methods. We present two model series of dynamical opacity-sampling models of Mira variables which have (1) 1/3 solar metallicity; and (2) “mild” S-type C/O abundance ratio ([C/O] = 0.9) with typical Zr enhancement (solar +1.0). These series are compared to a previously studied solar-abundance series which has similar fundamental parameters (mass, luminosity, period, radius) that are close to those of o Cet.

Results. Both series show noticeable effects of abundance upon stratifications and infrared colours but cycle-to-cycle differences mask these effects at most pulsation phases, with the exception of a narrow-water-filter colour near minimum phase.