Substellar multiplicity in the Hyades cluster

Abstract

We present the first high-angular resolution survey for multiple systems among very low-mass stars and brown dwarfs in the Hyades open cluster. Using the Keck\,II adaptive optics system, we observed a complete sample of 16 objects with estimated masses $\lesssim$0.1 Msun. We have identified three close binaries with projected separation $\lesssim$0.11", or $\lesssim$5 AU. A number of wide, mostly faint candidate companions are also detected in our images, most of which are revealed as unrelated background sources based on astrometric and/or photometric considerations. The derived multiplicity frequency, 19+13/-6 % over the 2-350 AU range, and the rarity of systems wider than 10 AU are both consistent with observations of field very low-mass objects. In the limited 3-50 AU separation range, the companion frequency is essentially constant from brown dwarfs to solar-type stars in the Hyades cluster, which is also in line with our current knowledge for field stars. Combining the binaries discovered in this surveys with those already known in the Pleiades cluster reveals that very low-mass binaries in open clusters, as well as in star-forming regions, are skewed toward lower mass ratios ($0.6\lesssim q\lesssim 0.8$) than are their field counterparts, a result that cannot be accounted for by selection effects. Although the possibility of severe systematic errors in model-based mass estimates for very low-mass stars cannot be completely excluded, it is unlikely to explain this difference. We speculate that this trend indicates that surveys among very low-mass field stars may have missed a substantial population of intermediate mass ratio systems, implying that these systems are more common and more diverse than previously thought.

Accepted for publication in Astronomy & Astrophysics; 11 pages, 6 figures

References in corpus (9)

• Hubble Space Telescope NICMOS Observations of T Dwarfs: Brown Dwarf Multiplicity and New Probes of the L/T Transition
• A Survey for Spectroscopic Binaries Among Very Low-Mass Stars
• Discovery of a wide companion near the deuterium burning mass limit in the Upper Scorpius association
• Brown dwarfs and very low mass stars in the Hyades cluster : a dynamically evolved mass function
• Astrometric orbit of a low-mass companion to an ultracool dwarf
• The Detection of Low Mass Companions in Hyades Cluster Spectroscopic Binary Stars
• The binary companion mass ratio distribution: an imprint of the star formation process?
• The GL 569 Multiple System
• L dwarfs in the Hyades

Cited by in corpus (24)

• SpeX Spectroscopy of Unresolved Very Low Mass Binaries. II. Identification of Fourteen Candidate Binaries with Late-M/Early-L and T Dwarf Components
• The statistical properties of stars and their dependence on metallicity: the effects of opacity
• K2 Rotation Periods for low-mass Hyads and the Implications for Gyrochronology
• Direct Imaging Discovery and Dynamical Mass of a Substellar Companion Orbiting an Accelerating Hyades Sun-like Star with SCExAO/CHARIS
• The inflated radii of M-dwarfs in the Pleiades
• A 3D view of the Hyades stellar and sub-stellar population
• A Brown Dwarf Census from the SIMP Survey
• The Gaia-ESO Survey: Membership probabilities for stars in 32 open clusters from 3D kinematics
• An unusual face-on spiral in the wind of the M-type AGB star EP Aquarii
• Results from The COPAINS Pilot Survey: four new brown dwarfs and a high companion detection rate for accelerating stars
• Atomium: A high-resolution view on the highly asymmetric wind of the AGB star Pi1 Gruis. I. First detection of a new companion and its effect on the inner wind
• ALMA detection of a tentative nearly edge-on rotating disk around the nearby AGB star R~Doradus
• Single stars in the Hyades open cluster. Fiducial sequence for testing stellar and atmospheric models
• The dynamical evolution of low-mass hydrogen-burning stars, brown dwarfs and planetary-mass objects formed through disc fragmentation
• ALMA observations of the nearby AGB star L${}_2$ Puppis. II. Gas disk properties derived from ${}^{12}$CO and ${}^{13}$CO $J=$3$-$2 emission
• Simplified models of stellar wind anatomy for interpreting high-resolution data: Analytical approach to embedded spiral geometries
• Radius Inflation at Low Rossby Number in the Hyades Cluster
• KMT-2016-BLG-1820 and KMT-2016-BLG-2142: Two Microlensing Binaries Composed of Planetary-mass Companions and Very-Low-Mass Primaries
• The effects of binary stars on galaxies and metal-enriched gas during reionization
• Long-term stability of planets in and around binary stars
• Simplified models of circumstellar morphologies for interpreting high-resolution data. Analytical approach to the equatorial density enhancement
• On the Binary Frequency of the Lowest Mass Members of the Pleiades with Hubble Space Telescope Wide Field Camera 3
• Spatial differences between stars and brown dwarfs: a dynamical origin?
• Two close binaries across the hydrogen-burning limit in the Praesepe open cluster