A remarkable change of the spectrum of the magnetic Of?p star HD148937 reveals evidence of an eccentric, high-mass binary

WADE, G A; SMOKER, J V; EVANS, C J; HOWARTH, I D; BARBA, R; COX, N L J; MORRELL, N; NAZÉ, Y; CAMI, J; FARHANG, A; WALBORN, N R; ARIAS, J; GAMEN, R

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2019 vol. 483 p. 2581 - 2591

0035-8711

We report new spectroscopic observations of the magnetic Of?p star HD148937 obtained since 2015 that differ qualitatively from its extensivehistorical record of weak, periodic spectral variations. This remarkablebehaviour represents clear evidence for an unprecedented change in thecharacter of variability of the star. In this paper, we describe the newspectral properties and compare them to the previous line profiles.Based on measurements of the radial velocities of the C III/N IIIemission lines near 4640 Å and the C IV absorption lines near 5800Å, we infer that HD 148937 is likely a high-mass, double-linedspectroscopic binary. Combining the spectroscopic orbit with an archivalinterferometric measurement of the apparent separation of the equalbrightness components, we tentatively conclude that HD 148937 consistsof two O-type stars with masses of approximately 34 and 49M⊙, orbiting in an eccentric (e = 0.75), long-period(Porb ? 26 yr) orbit. We discuss the potentialrelationship of the binary system to the peculiar properties of HD148937, and propose future observations to refine the orbital andstellar properties.