The heavy mass loss observed in evolved asymptotic giant branch (AGB) stars
is usually attributed to a two-stage process: atmospheric levitation by
pulsation-induced shock waves, followed by radiative acceleration of newly
formed dust grains. The dust transfers momentum to the surrounding gas through
collisions and thereby triggers a general outflow. Radiation-hydrodynamical
models of M-type AGB stars suggest that these winds can be driven by photon
scattering -- in contrast to absorption -- on Fe-free silicate grains of sizes
0.1--1\,μm. In this paper we study photometric constraints for wind-driving
dust species in M-type AGB stars, as part of an ongoing effort to identify
likely candidates among the grain materials observed in circumstellar
envelopes. To investigate the scenario of stellar winds driven by photon
scattering on dust, and to explore how different optical and chemical
properties of wind-driving dust species affect photometry we focus on two sets
of dynamical models atmospheres: (i) models using a detailed description for
the growth of Mg2SiO4 grains, taking into account both scattering and
absorption cross-sections when calculating the radiative acceleration, and (ii)
models using a parameterized dust description, constructed to represent
different chemical and optical dust properties. By comparing synthetic
photometry from these two sets of models to observations of M-type AGB stars we
can provide constraints on the properties of wind-driving dust species.
Photometry from wind models with a detailed description for the growth of
Mg2SiO4 grains reproduces well both the values and the time-dependent
behavior of observations of M-type AGB stars, providing further support for the
scenario of winds driven by photon scattering on dust.Comment: Accepted for publication in A&A. 15 pages, 14 figure