Discovery of the first τ Sco analogues: HD66665 and HD63425

Abstract

The B0.2 V magnetic starô τSco stands out from the larger population of massive OB stars due to its high X-ray activity, peculiar wind diagnostics and highly complex magnetic field. This Letter presents the discovery of the first two ôτSco analogues - HD66665 and HD63425, identified by the striking similarity of their ultraviolet (UV) spectra to that of ôτSco. ESPaDOnS spectropolarimetric observations were secured by the Magnetism in Massive StarsCFHTLarge Program, in order to characterize the stellar and magnetic properties of these stars. CMFGEN modelling of optical ESPaDOnS spectra and archived IUE UV spectra showed that these stars have stellar parameters similar to those of ôτSco. A magnetic field of similar surface strength is found on both stars, reinforcing the connection between the presence of a magnetic field and wind peculiarities. However, additional phase-resolved observations will be required in order to assess the potential complexity of the magnetic fields and verify if the wind anomalies are linked to this property. © 2011 The Authors. Monthly Notices of the Royal Astronomical Society © 2011 RAS.