The integrated radio spectrum of G2.4+1.4

Abstract

ABSTRACT The Galactic source G2.4+1.4 is an optical and radio nebula containing an extreme Wolf–Rayet star. At one time, this source was regarded as a supernova remnant, because of its apparent non-thermal radio spectrum, although this was based on limited observations. Subsequent observations instead supported a flat, optically thin thermal radio spectrum for G2.4+1.4, and it was identified as a photoionized, mass-loss bubble, not a supernova remnant. Recently, however, it has been claimed that this source has a non-thermal integrated radio spectrum. I discuss the integrated radio flux densities available for G2.4+1.4 from a variety of surveys, and show that it has a flat spectrum at gigahertz frequencies (with a spectral index α of 0.02 ± 0.08, where flux density S scales with frequency ν as S ∝ ν−α).