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

Research output: Contribution to journalArticlepeer-review


  • A. von Boetticher
  • Didier Queloz
  • S. Gill
  • M. Lendl
  • L. Delrez
  • D.~R. Anderson
  • A. Collier Cameron
  • F. Faedi
  • Michael Gillon
  • Y. Gómez Maqueo Chew
  • L. Hebb
  • C. Hellier
  • E. Jehin
  • P.~F.~L. Maxted
  • D.~V. Martin
  • F. Pepe
  • D. Pollacco
  • D. Ségransan
  • B. Smalley
  • S. Udry
  • R. West

Colleges, School and Institutes


We report the discovery of an eclipsing binary system with mass-ratio q tilde 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 plusmn 4 M$_Jup$ (0.081 M$_⊙$) and a radius of 0.84$^+ 0.14$$_-0.04$R$_Jup$ (0.084 R$_⊙$) that is comparable to that of Saturn. EBLM J0555-57Ab has a surface gravity log g$_2$ =5.50$^+ 0.03$$_-0.13$ and is one of the densest non-stellar-remnant objects currently known. These measurements are consistent with models of low-mass stars. The photometry tables and radial velocities are only available at the CDS and on demand via anonymous ftp to ( or via


Original languageEnglish
Pages (from-to)L6
JournalAstronomy and Astrophysics
Publication statusPublished - 1 Aug 2017


  • stars: individual: EBLM J0555-57Ab, binaries: eclipsing, binaries: spectroscopic, stars: low-mass, techniques: spectroscopic, techniques: photometric