  In this paper, by considering an absorption probability independent of photon
wavelength, we show that current type Ia supernovae (SNe Ia) and gamma ray
burst (GRBs) observations plus high-redshift measurements of the cosmic
microwave background (CMB) radiation temperature support cosmic acceleration
regardless of the transparent-universe assumption. Two flat scenarios are
considered in our analyses: the $\Lambda$CDM model and a kinematic model. We
consider $\tau(z)=2\ln(1+z)^{\varepsilon}$, where $\tau(z)$ denotes the opacity
between an observer at $z=0$ and a source at $z$. This choice is equivalent to
deforming the cosmic distance duality relation as $D_LD^{-1}_A = (1 +
z)^{2+\varepsilon}$ and, if the absorption probability is independent of photon
wavelength, the CMB temperature evolution law is
$T_{CMB}(z)=T_0(1+z)^{1+2\varepsilon/3 }$. By marginalizing on the
$\varepsilon$ parameter, our analyses rule out a decelerating universe at 99.99
\% c.l. for all scenarios considered. Interestingly, by considering only SNe Ia
and GRBs observations, we obtain that a decelerated universe indicated by
$\Omega_{\Lambda} \leq 0.33$ and $q_0 > 0$ is ruled out around 1.5$\sigma$ c.l.
and 2$\sigma$ c.l., respectively, regardless of the transparent-universe
assumption.
