Discovery of a highly magnetic He-sdO from a double-degenerate binary merger

Vol. 658
1. Letters

Discovery of a highly magnetic He-sdO from a double-degenerate binary merger

The paper by Dorsch et al. reports the discovery of the first strong magnetic field found in any helium-rich hot subdwarf star of spectral type O (He-sdO). The field, which is on the order of 350 kG in strength, is toward the high end of the range of fields that one might hope to discover in such stars from Zeeman split absorption lines. By combining the spectroscopic data, the Gaia parallax, and the spectral energy distribution, the mass, radius, and luminosity of the star can also be derived. The detection of a strong magnetic field, its unusually high mass (0.93 Msun), and the lack of evidence for a close stellar companion provide overwhelming evidence for J0809-2627 being the result of a double-degenerate merger that produced a stably helium-burning star.