Constraining the parameter space of the one-zone synchrotron-self-Compton model for GeV-TeV detected BL Lac objects

Abstract: The one-zone synchrotron-self-Compton (SSC) model aims to describe the spectral energy distribution (SED) of BL Lac objects via synchrotron emission by a non-thermal population of electrons and positrons in a single homogeneous emission region, partially upscattered to gamma-rays by the particles themselves. The model is usually considered as degenerate, given that the number of free parameters is higher than the number of observables. It is thus common to model the SED by choosing a single set of values for the SSC-model parameters that provide a good description of the data, without studying the entire parameter space. We present here a new numerical algorithm which permits us to find the complete set of solutions, using the information coming from the detection in the GeV and TeV energy bands. The algorithm is composed of three separate steps: we first prepare a grid of simulated SEDs and extract from each SED the values of the observables; we then parametrize each observable as a function of the SSC parameters; we finally solve the system for a given set of observables. We iteratively solve the system to take into account uncertainties in the values of the observables, producing a family of solutions. We present a first application of our algorithm to the typical high-frequency-peaked BL Lac object 1RXS J101015.9-311909, provide constraints on the SSC parameters, and discuss the result in terms of our understanding of the blazar emitting region.