A compact multi-planet system around a bright nearby star from the Dispersed Matter Planet Project

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Abstract

To put the Solar System’s terrestrial planets in context, the detection and characterization of low-mass exoplanets is important but challenging. The Dispersed Matter Planet Project targets stars with anomalously low Ca ii H and K chromospheric emission, indicative of circumstellar absorbing gas. Here we report high-precision, high-cadence radial-velocity measurements of the F8V star DMPP-1 (HD 38677). These were motivated by depressed Ca ii H and K line cores indicative of short-period, ablating planets producing circumstellar gas. We find a compact planetary system with orbital periods of about 2.9–19 days, comprising three super-Earth-mass planets (about 3–10 M) and one Neptune-mass planet (about 24 M). The irradiated super-Earths may be remnant cores of giant planets after mass loss while crossing the Neptune desert. A priori inferences about the presence of short-period planets enabled the efficient discovery of the DMPP-1 planets. We anticipate informative follow-up characterization studies.

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Fig. 1: RV measurements and Keplerian solutions corresponding to parameters in Table 2.
Fig. 2: Log-likelihood (ΔlogL) periodograms of the window function and the four-Keplerian search for the complete dataset.
Fig. 3: Radial velocity modulations for each planet in our preferred solution.
Fig. 4: Log-likelihood periodograms as in Fig. 2 with inclusion of S-index activity correlation.
Fig. 5: Radial velocity modulations for each Keplerian signal in the solution incorporating an S-index correlation.
Fig. 6: Numerical simulations of the preferred four-Keplerian solution for DMPP-1 (Table 2a).

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request. All RV data, collected under ESO programmes 096.C-0876(A) and 098.C-0269(A), 098.C0499(A), 098.C0269(B), 099.C-0798(A) and 0100.C-0836(A), are publicly available from the ESO archive (http://archive.eso.org).

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Acknowledgements

This work is based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programmes 096.C-0876(A) and 098.C-0269(A), 098.C0499(A), 098.C0269(B), 099.C-0798(A) and 0100.C-0836(A). D.S. was supported by an STFC studentship. C.A.H. and J.R.B. were supported by STFC Consolidated Grants ST/L000776/1 and ST/P000584/1. G.A.-E. was supported by STFC Consolidated Grant ST/P000592/1. J.S.J. acknowledges support by FONDECYT grant 1161218 and partial support from CONICYT project Basal AFB-170002. M.R.D. acknowledges the support of CONICYT-PFCHA/Doctorado Nacional-21140646, Chile, and project Basal AFB-170002. These results were based on observations awarded by ESO using HARPS. This research has made use of the SIMBAD data base, operated at CDS, Strasbourg, France.

Author information

D.S. performed target selection, and contributed to writing of proposals, making figures, initial RV analyses and technical details of the paper. C.A.H. plans and leads all aspects of the DMPP collaboration, secured the funding, and wrote the proposals and much of the paper. J.R.B. contributed to proposals, performed final RV analyses, wrote the initial paper draft and the technical sections and made the figures. G.A.-E. provided software and expertise. L.F. contributed to the analysis and proposal writing. J.S.J. and M.G.S. provided expertise on stellar activity, the log RHK metric and contributed stellar parameter analyses. D.S., C.A.H., J.R.B., J.P.J.D., J.C. and M.R.D. performed observations with HARPS. All authors were given the opportunity to review the results and comment on the manuscript.

Correspondence to C. A. Haswell.

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Peer review information Nature Astronomy thanks Teruyuki Hirano for their contribution to the peer review of this work.

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Supplementary Information

Supplementary text, Supplementary Table 1, Supplementary references, Supplementary Figs. 1–4.

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Staab, D., Haswell, C.A., Barnes, J.R. et al. A compact multi-planet system around a bright nearby star from the Dispersed Matter Planet Project. Nat Astron (2019). https://doi.org/10.1038/s41550-019-0974-x

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