Gamma-ray astronomy

Abstract:

In this paper we present high spatial resolution radio images of the puzzling binary system β Lyrae obtained with MERLIN at 5 GHz. We find a nebula surrounding the binary with a brightness temperature of (11000 ± 700) K approximately 40 AU across. This definitively confirms the thermal origin of the radio emission, which is consistent with emission from the wind of the B6-8 II component (mass loss of order of 10^-7 M⊙yr^-1), ionized by the radiation field of the hotter companion. This nebula, surrounding the binary, is the proof that β Lyrae evolved in a non-conservative way, i. e. not all the mass lost by the primary is accretted by the secondary, and present measurements indicate that almost 0.015 M⊙ had been lost from the system since the onset of the Roche lobe overflow phase. Moreover, the nebula is aligned with the jet-like structures inferred from recent optical measurements, indicating a possible connection among them.