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arXiv · 1706.08781

The EBLM project III. A Saturn-size low-mass star at the hydrogen-burning limit

Alexander von Boetticher·Amaury H. M. J. Triaud·Didier Queloz·Sam Gill·Monika Lendl·Laetitia Delrez·David R. Anderson·Andrew Collier Cameron·Francesca Faedi·Michaël Gillon·Yilen Gómez Maqueo Chew·Leslie Hebb·Coel Hellier·Emmanuël Jehin·Pierre F. L. Maxted·David V. Martin·Francesco Pepe·Don Pollacco·Damien Ségransan·Barry Smalley·Stéphane Udry·Richard West
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Abstract

We report the discovery of an eclipsing binary system with mass-ratio q $\sim$ 0.07. After identifying a periodic photometric signal received by WASP, we obtained CORALIE spectroscopic radial velocities and follow-up light curves with the Euler and TRAPPIST telescopes. From a joint fit of these data we determine that EBLM J0555-57 consists of a sun-like primary star that is eclipsed by a low-mass companion, on a weakly eccentric 7.8-day orbit. Using a mass estimate for the primary star derived from stellar models, we determine a companion mass of $85 \pm 4 M_{\rm Jup}$ ($0.081M_{\odot}$) and a radius of $0.84^{+0.14}_{-0.04} R_{\rm Jup}$ ($0.084 R_{\odot}$) that is comparable to that of Saturn. EBLM J0555-57Ab has a surface gravity $\log g_\mathrm{2} = 5.50^{+0.03}_{-0.13}$ and is one of the densest non-stellar-remnant objects currently known. These measurements are consistent with models of low-mass stars.

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Alexander von Boetticher, Amaury H. M. J. Triaud, Didier Queloz, Sam Gill, Monika Lendl, Laetitia Delrez, David R. Anderson, Andrew Collier Cameron, Francesca Faedi, Michaël Gillon, Yilen Gómez Maqueo Chew, Leslie Hebb, Coel Hellier, Emmanuël Jehin, Pierre F. L. Maxted, David V. Martin, Francesco Pepe, Don Pollacco, Damien Ségransan, Barry Smalley, Stéphane Udry, Richard West. 2017-06-27. The EBLM project III. A Saturn-size low-mass star at the hydrogen-burning limit. https://doi.org/10.1051/0004-6361/201731107

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