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Sairam, Lalitha; Triaud, Amaury H M J; Baycroft, Thomas A; Orosz, Jerome; Boisse, Isabelle; Heidari, Neda; Sebastian, Daniel; Dransfield, Georgina; Martin, David V; Santerne, Alexandre and Standing, Matthew R.
(2023).
DOI: https://doi.org/10.1093/mnras/stad3136
Abstract
Ongoing ground-based radial-velocity observations seeking to detect circumbinary planets focus on single-lined binaries even though over 9 in every 10 binary systems in the solar neighbourhood are double lined. Double-lined binaries are on average brighter, and should in principle yield more precise radial velocities. However, as the two stars orbit one another, they produce a time-varying blending of their weak spectral lines. This makes an accurate measure of radial velocities difficult, producing a typical scatter of . This extra noise prevents the detection of most orbiting circumbinary planets. We develop two new data-driven approaches to disentangle the two stellar components of a double-lined binary, and extract accurate and precise radial velocities. Both approaches use a Gaussian process regression, with the first one working in the spectral domain, whereas the second works on cross-correlated spectra. We apply our new methods to TIC 172900988, a proposed circumbinary system with a double-lined binary, and detect a circumbinary planet with an orbital period of
, different than previously proposed. We also measure a significant residual scatter, which we speculate is caused by stellar activity. We show that our two data-driven methods outperform the traditionally used TODCOR and TODMOR, for that particular binary system.
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