SCExAO/CHARIS Direct Imaging of A Low-mass Companion at A Saturn-like Separation from an Accelerating Young A7 Star

Jeffrey Chilcote, Taylor Tobin, Thayne Currie, Timothy D. Brandt, Tyler D. Groff, Masayuki Kuzuhara, Olivier Guyon, Julien Lozi, Nemanja Jovanovic, Ananya Sahoo, Vincent Deo, Eiji Akiyama, Markus Janson, Jill Knapp, Jungmi Kwon, Michael W. McElwain, Jun Nishikawa, Kevin Wagner, Krzysztof Hełminiak, Nour SkafMotohide Tamura

Research output: Contribution to journalArticlepeer-review

Abstract

We present the SCExAO direct imaging discovery and characterization of a low-mass companion to the nearby young A7IV star, HD 91312. SCExAO/CHARIS JHK (1.1-2.4 μm) spectra and SCExAO/HiCIAO H-band imaging identify the companion over a two year baseline in a highly inclined orbit with a maximum projected separation of 8 au. The companion, HD 91312 B, induces an 8.8σ astrometric acceleration on the star as seen with the Gaia & Hipparcos satellites and a long-term radial-velocity trend as previously identified by Borgniet et al. HD 91312 B's spectrum is consistent with that of an early-to-mid M dwarf. Hipparcos and Gaia absolute astrometry, radial-velocity data, and SCExAO/CHARIS astrometry constrain its dynamical mass to be 0.337-0.044+0.042 M o˙, consistent with - but far more precise than - masses derived from spectroscopy, and favors a nearly edge-on orbit with a semimajor axis of ∼9.7 au. This work is an example of precisely characterizing properties of low-mass companions at solar system-like scales from a combination of direct imaging, astrometry, and radial-velocity methods.

Original languageEnglish (US)
Article number251
JournalAstronomical Journal
Volume162
Issue number6
DOIs
StatePublished - Dec 1 2021

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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