# An ablating 2.6 M⊕ planet in an eccentric binary from the Dispersed Matter Planet Project

## Abstract

Earth-mass exoplanets are difficult to detect. The Dispersed Matter Planet Project (DMPP) identifies stars that are likely to host the most detectable low-mass exoplanets. The star DMPP-3 (HD 42936) shows signs of circumstellar absorption, indicative of mass loss from ablating planets. Here, we report the radial velocity discovery of a highly eccentric 507 d binary companion and a hot super-Earth-mass planet in a 6.67 d orbit around the primary star. DMPP-3A is a solar-type star while DMPP-3B is just massive enough to fuse hydrogen. The binary, with semi-major axis 1.22 ± 0.02 au, is considerably tighter than others known to host planets orbiting only one of the component stars. The configuration of the DMPP-3 planetary system is rare and indicates dynamical interactions, though the evolutionary history is not entirely clear. DMPP-3A b is possibly the residual core of a giant planet precursor, consistent with the inferred circumstellar gas shroud.

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## 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. Raw and processed spectra can be obtained from the European Southern Observatory’s data archive at http://archive.eso.org.

## Code availability

The SPECIES code13 is publicly available at https://github.com/msotov/SPECIES/ and the EMPEROR code at https://github.com/ReddTea/astroEMPEROR.

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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 081.C-0148(A), 088.C-0662(A) and 091.C-0866(C), 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 are based on observations awarded by ESO, using HARPS. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France.

## Author information

J.R.B. contributed to proposals, performed RV analyses and wrote the paper. C.A.H. led all aspects of the DMPP collaboration, secured the funding, wrote the proposals and co-wrote the paper. D.S. performed target selection, contributed to writing of proposals, initial RV analyses and technical details of the paper. G.A.-E. provided software and expertise. L.F. contributed to the analysis and proposal writing. J.S.J., M.G.S. and P.A.P.R. provided expertise on stellar activity, the log HK metric, contributed stellar parameter analyses and performed RV solution checks. 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 John R. Barnes.

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## Supplementary information

### Supplementary Information

Supplementary text and Table 1.

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Barnes, J.R., Haswell, C.A., Staab, D. et al. An ablating 2.6 M planet in an eccentric binary from the Dispersed Matter Planet Project. Nat Astron (2019). https://doi.org/10.1038/s41550-019-0972-z

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• ### Dispersed Matter Planet Project discoveries of ablating planets orbiting nearby bright stars

• Carole A. Haswell
• , Daniel Staab
• , John R. Barnes