Discovery of the first tau Sco analogues: HD 66665 and HD 63425

V. Petit (1), D. L. Massa (2), W. L. F. Marcolino (3), G. A. Wade (4), R. Ignace (5) and the MiMeS Collaboration

(1) Department of Geology & Astronomy, West Chester University, West Chester, PA 19383, USA.
(2) Space Telescope Science Institute, 3700 N. San Martin Drive, Baltimore, MD 21218, USA.
(3) Observatorio Nacional-MCT, Rua Jose Cristino, 77, CEP 20921-400, Sao Cristovao, Rio de Janeiro, Brasil.
(4) Department of Physics, Royal Military College of Canada, PO Box 17000, Station Forces, Kingston, ON K7K 4B4, Canada.
(5) Department of Physics & Astronomy, East Tennessee State University, Box 70652, Johnson City, TN 37614, USA.

The B0.2 V magnetic star tau Sco 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 tau Sco analogues – HD 66665 and HD 63425, identified by the striking similarity of their ultraviolet (UV) spectra to that of tau Sco. ESPaDOnS spectropolarimetric observations were secured by the Magnetism in Massive Stars CFHT Large 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 tau Sco. 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.

Reference: MNRAS, in press. Available in Early View.
Status: Manuscript has been accepted