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DMPP-4: candidate sub-Neptune mass planets orbiting a naked-eye star

Barnes, J. R., Standing, M. R., Haswell, C. A., Staab, D., Doherty, J. P. J., Waller-Bridge, M., Fossati, L., Soto, M., Anglada-Escudé, G., Llama, J., McCune, C. and Lewis, F.W. 2023. DMPP-4: candidate sub-Neptune mass planets orbiting a naked-eye star. Monthly Notices of the Royal Astronomical Society 524 (4) , pp. 5196-5212. 10.1093/mnras/stad2109

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We present radial velocity measurements of the very bright (V ∼ 5.7) nearby F star, DMPP-4 (HD 184960). The anomalously low Ca II H&K emission suggests mass-loss from planets orbiting a low activity host star. Periodic radial velocity variability with ∼10 m s−1 amplitude is found to persist over a >4 yr time-scale. Although the non-simultaneous photometric variability in four TESS sectors supports the view of an inactive star, we identify periodic photometric signals and also find spectroscopic evidence for stellar activity. We used a posterior sampling algorithm that includes the number of Keplerian signals, Np, as a free parameter to test and compare (1) purely Keplerian models (2) a Keplerian model with linear activity correlation and (3) Keplerian models with Gaussian processes. A preferred model, with one Keplerian and quasi-periodic Gaussian process indicates a planet with a period of d and corresponding minimum mass of M⊕. Without further high-time resolution observations over a longer time-scale, we cannot definitively rule out the purely Keplerian model with two candidates planets with d, minimum mass M⊕ and d and corresponding minimum mass of M⊕. The candidate planets lie in the region below the lower-envelope of the Neptune Desert. Continued mass-loss may originate from the highly irradiated planets or from an as yet undetected body in the system.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Publisher: Oxford University Press
ISSN: 0035-8711
Date of First Compliant Deposit: 30 April 2024
Date of Acceptance: 8 July 2023
Last Modified: 30 Apr 2024 09:09

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