Discovery of Seven Companions to Intermediate-mass Stars with Extreme Mass Ratios in the Scorpius–Centaurus Association
We report the detection of seven low-mass companions to intermediate-mass stars (SpT B/A/F; ~ 1.5–4.5 M_⊙) in the Scorpius–Centaurus (Sco–Cen) Association using nonredundant aperture masking interferometry. Our newly detected objects have contrasts ΔL' ≈ 4–6, corresponding to masses as low as ~20 M_(Jup) and mass ratios of q ≈ 0.01–0.08, depending on the assumed age of the target stars. With projected separations ρ ≈ 10–30 AU, our aperture masking detections sample an orbital region previously unprobed by conventional adaptive optics imaging of intermediate-mass Sco–Cen stars covering much larger orbital radii (~30–3000 AU). At such orbital separations, these objects resemble higher-mass versions of the directly imaged planetary mass companions to the 10–30 Myr, intermediate-mass stars HR 8799, β Pictoris, and HD 95086. These newly discovered companions span the brown dwarf desert, and their masses and orbital radii provide a new constraint on models of the formation of low-mass stellar and substellar companions to intermediate-mass stars.
© 2015 American Astronomical Society. Received 2015 March 6; accepted 2015 May 12; published 2015 June 4. We thank the anonymous referee for several helpful comments. We also thank Isabelle Baraffe and Giles Chabrier for producing versions of their evolutionary models at customized ages. This work was performed in part under contract with the California Institute of Technology (Caltech) funded by NASA through the Sagan Fellowship Program and an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-1203023. A.L.K. was suported by a Clay Fellowship as well as NASA through Hubble Fellowship grant 51257.01 awarded by the STScI, which is operated by AURA, Inc., for NASA, under contract NAS 5-26555. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and NASA. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.
Submitted - 1505.03858v1.pdf
Published - 2041-8205_806_1_L9.pdf