A VLBI study of the wind-wind collision region in the massive multiple HD 167971

Abstract

Context. Colliding winds in massive binaries are able to accelerate particles up to relativistic speeds as the result of the interaction between the winds of the different stellar components. HD 167971 exhibits this phenomenology which makes it a strong radio source. Aims. We aim at characterizing the morphology of the radio emission and its dependence on the orbital motion, traced independently by NIR-interferometry, of the spectroscopic binary and the tertiary component that conforms HD 167971. Methods. We analyze 2006 and 2016 very long baseline interferometric data at C and X bands. We complement our analysis with a geometrical model of the wind-wind collision region, and with an astrometric description of the system. Results. We confirm that the detected non-thermal radio emission is associated with the wind-wind collision region of the spectroscopic binary and the tertiary component in HD 167971. The wind-wind collision region changes orientation in agreement with the orbital motion of the tertiary around the spectroscopic binary. The total intensity also changes between the two observing epochs in a way inversely proportional to the separation between the SB and T, with a negative-steep spectral index typical of an optically thin synchrotron emission possibly steepened by an inverse Compton cooling effect. The wind-wind collision bow-shock shape and its position with respect to the stars indicates that the wind momentum from the spectroscopic binary is stronger than that of the tertiary. Finally, the astrometric solution derived for the stellar system and the wind-wind collision region is consistent with independent Gaia data.

Accepted for publication in Astronomy and Astrophysics, 7 pages, 6 figures

References in corpus (6)

• The Gaia mission
• Magnetic Cycles and Rotation Periods of Late Type Stars from photometric time series
• Radio, X-ray, and gamma-ray Emission Models of the Colliding Winds Binary WR 140
• Asymptotic Opening Angles for Colliding-Wind Bow Shocks: the Characteristic-Angle Approximation
• Non-thermal radio emission from O-type stars. II. HD 167971
• GRAVITY spectro-interferometric study of the massive multiple stellar system HD 93 206 A

Cited by in corpus (6)

• Radio observations of massive stars in the Galactic centre: The Arches Cluster
• Multiplicity of northern bright O-type stars with optical long baseline interferometry
• Radio study of the colliding wind binary HD93129A near periastron and its surroundings
• A multi-frequency, multi-epoch radio continuum study of the Arches cluster with the VLA
• Investigating particle acceleration dynamics in interpenetrating magnetized collisionless super-critical shocks
• Radio observations of massive stars in the Galactic centre: The Quintuplet cluster