We study observational viability of Natural Inflation with a tachyon field as inflation. By obtaining the main perturbation parameters in this model, we perform a numerical analysis on the parameter space of the model and in confrontation with 68% and 95% CL regions of Planck2015 data. By adopting a warped background geometry, we nd some new constraints on the width of the potential in terms of its height and the warp factor. We show that the Tachyon Natural In ation in the large width limit recovers the tachyon model with a 2 potential which is consistent with Planck2015 observational data. Then we focus on the reheating era after in ation by treating the number of e-folds, temperature and the e ective equation of state parameter in this era. Since it is likely that the value of the e ective equation of state parameter during the reheating era to be in the range 0 !e 1 3 , we obtain some new constraints on the tensor to scalar ratio, r, as well as the e-folds number and reheating temperature in this Tachyon Natural In ation model. In particular, we show that a prediction of this model is r 8 3 ns, where ns is the scalar spectral tilt, ns = 1ns. In this regard, given that from the Planck2015 data we have ns = 0:032 (corresponding to ns = 0:968), we get r 0:085.
