Dynamic shear-modulus data are presented for the two silicone oils DC704 and
DC705 for frequencies between 1 mHz and 10 kHz at temperatures covering more
than five decades of relaxation-time variation. The data are fitted to the
alpha part of a phenomenological model previously shown to describe well the
dynamic shear modulus of squalane, which has a large beta process [Hecksher
\textit{et al.}, J. Chem. Phys. \textbf{146}, 154504 (2017)]; that model is
characterized by additivity of the alpha and beta shear compliance and by a
high-frequency decay of the alpha process in proportion to Οβ1/2 in
which Ο is the angular frequency. The fits of the alpha part of this
model to the DC704 and DC705 data are compared to fits by a Havriliak-Negami
type model, the Barlow-Erginsav-Lamb model, and a Cole-Davidson type model. At
all temperatures the best fit is obtained by the alpha part of the squalane
model. This strengthens the conjecture that so-called tβ-relaxation,
leading to high-frequency decays proportional to Οβ1/2, is a general
characteristic of the alpha relaxation of supercooled liquids [Dyre, Phys. Rev.
E {\bf 74}, 021502 (2006); Nielsen \textit{et al.}, J. Chem. Phys.
\textbf{130}, 154508 (2009); Pabst \textit{et al.}, J. Phys. Chem. Lett.
\textbf{12}, 3685 (2021)]