Non-synchronous rotations in massive binary systems

PUTKURI, C.; GAMEN, R.; MORRELL, N. I.; SIMÓN-DÍAZ, S.; BARBÁ, R. H.; FERRERO, G. A.; ARIAS, J. I.; SOLIVELLA, G.

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Año: 2018 vol. 618 p. 174 - 183

0004-6361

Context. Most massive stars are in binary or multiple systems. Severalmassive stars have been detected as double-lined spectroscopic binariesand among these, the OWN Survey has detected a non-negligible numberwhose components show very different spectral line broadening (i.e.,projected rotational velocities). This fact raises a discussion aboutthe contributing processes, such as angular-momentum transfer and tidalforces. Aims: We seek to constrain the physical and evolutionarystatus of one of such systems, the O+O binary HD93343. Methods: We analyzed a series of high-resolutionmultiepoch optical spectra to determine the orbital parameters,projected rotational velocities, and evolutionary status of the system. Results: HD 93343 is a binary system comprisedof two O7.5 Vz stars that each have minimum masses of approximately 22M⊙ in a wide and eccentric orbit (e = 0.398±0.004;P = 50.432±0.001 d). Both stars have very similar stellarparameters, and hence ages. As expected from the qualitative appearanceof the combined spectrum of the system, however, these stars have verydifferent projected rotational velocities ( 65 and 325 kms-1, respectively). Conclusions: The orbits andstellar parameters obtained for both components seem to indicate thattheir youth and relative separation is enough to discard the effects ofmass transfer and tidal friction. Thus, non-synchronization should beintrinsic to their formation.