The orbital kinematics of η Carinae over three periastra with a possible detection of the elusive secondary's motion

March 2023 • 2023MNRAS.519.5882S

Authors • Strawn, Emily • Richardson, Noel D. • Moffat, Anthony F. J. • Ibrahim, Nour • Lane, Alexis • Pickett, Connor • Chené, André-Nicolas • Corcoran, Michael F. • Damineli, Augusto • Gull, Theodore R. • Hillier, D. John • Morris, Patrick • Pablo, Herbert • Thomas, Joshua D. • Stevens, Ian R. • Teodoro, Mairan • Weigelt, Gerd

Abstract • The binary η Carinae is the closest example of a very massive star, which may have formed through a merger during its Great Eruption in the mid-19th century. We aimed to confirm and improve the kinematics using a spectroscopic data set taken with the Cerro Tololo Inter-American Observatory 1.5-m telescope over the time period of 2008-2020, covering three periastron passages of the highly eccentric orbit. We measure line variability of H α and H β, where the radial velocity and orbital kinematics of the primary star were measured from the H β emission line using a bisector method. At phases away from periastron, we observed the He II 4686 emission moving opposite the primary star, consistent with a possible Wolf-Rayet companion, although with a seemingly narrow emission line. This could represent the first detection of emission from the companion.