BlaST -- A Machine-Learning Estimator for the Synchrotron Peak of Blazars

Abstract

Active Galaxies with a jet pointing towards us, so-called blazars, play an important role in the field of high-energy astrophysics. One of the most important features in the classification scheme of blazars is the peak frequency of the synchrotron emission ($\nu_{\rm peak}^S$) in the spectral energy distribution (SED). In contrast to standard blazar catalogs that usually calculate the $\nu_{\rm peak}^S$ manually, we have developed a machine-learning algorithm - BlaST - that not only simplifies the estimation, but also provides a reliable uncertainty evaluation. Furthermore, it naturally accounts for additional SED components from the host galaxy and the disk emission, which may be a major source of confusion. Using our tool, we re-estimate the synchrotron peaks in the Fermi 4LAC-DR2 catalog. We find that BlaST, improves the $\nu_{\rm peak}^S$ estimation especially in those cases where the contribution of components not related to the jet is important.