SAFARI - I. A SPHERE discovery of a super metal-rich M-dwarf companion to the star HD 86006
Abstract
We report the direct detection of a fully convective, early-to-mid M-dwarf companion orbiting the star HD 86006, using ESO-SPHERE during Science Verification as part of the SAFARI program. HARPS+CORALIE radial velocity measurements first indicated a possible companion. Such work highlights the synergies that are now possible between these two observing methods. We studied the companion by comparing our observed spectra with BT-Settl models and template spectra, measuring spectral indices to obtain a spectral type, and used a joint radial velocity and astrometric fit to simulate the companion's orbit. The companion was found to be 4.14 mag fainter than the primary in the H2 band, residing at a physical separation of ∼25 au, with a Teff and spectral type of 3321 ± 111 K and M 4.1 ± 1.1, respectively. We note that the age derived from BT-Settl models for such a star is too low by over two orders of magnitude, similar to other known field mid-M stars. We searched for the radial velocity companion to HD 90520 without any clear detection; however, we reached a low contrast level of ΔH2 = 10.3 mag (or 1.3 * 10-4) at 0.2 arcsec and 12.6 mag (or 10-5) at 0.5 arcsec, allowing us to rule out any low-mass companions with masses of 0.07 and 0.05 M⊙ at these separations. This discovery provides us with the exciting opportunity to better constrain the mass-luminosity relation for low-mass stars in the super metal-rich domain, expanding our understanding of the most-common types of stars and substellar objects.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- October 2018
- DOI:
- 10.1093/mnras/sty1716
- arXiv:
- arXiv:1806.10067
- Bibcode:
- 2018MNRAS.479.4958P
- Keywords:
-
- stars: low-mass;
- stars: solar-type;
- binaries: visual;
- techniques: radial velocities;
- instrumentation: adaptive optics;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- Accepted for publication in MNRAS