A benchmark survey of substellar companions -- a critical test of formation and evolution models

Project: Research project

Project Details

Description

A benchmark survey of substellar companions -- a critical test of formation and evolution models A benchmark survey of substellar companions -- a critical test of formation and evolution models Brown dwarfs represent the low-mass end of the IMF, and the most extreme mass ratio stellar binaries. It is expected that while the stellar IMF drops off moving toward lower masses, a separate distribution belonging to giant planets becomes more frequent as mass decreases. Recent radial velocity studies of this brown dwarf desert, however, suggest it only holds at very small separations (<100 days), and there is no evidence for a desert at wider separations probed by direct imaging. However, given the relative rarity of brown dwarf companions, it is difficult to trace this relationship in detail with a limited number of detections. The companion fraction and orbital architectures provide empirical constraints on formation models for both stellar and substellar systems. Detection of younger brown dwarfs requires only a few minutes of integration time with large ground-based telescopes equipped with adaptive optics (AO). We propose to perform a comprehensive, volume-limited search for stellar and substellar companions by utilizing the extensive set of multi-epoch high resolution imaging observations in the NASA Keck and HST archives, many of which have not been published to date, and the all-sky survey of WISE for the widest companions. From this uniform analysis, drawing upon the extensive NASA archives of both ground-based high resolution and space-based high sensitivity images, we will expand our list of candidates, and finalize any characterization of the companion properties with limited follow-up observations. Finally, we will generate contrast curves and completeness to companions for every star to determine the population-level properties of brown dwarf companions to high-mass stars. This sample will be over three times as large as previous surveys for stellar and substellar companions to B and A stars and will search an additional three decades in separation coverage compared to current substellar companion searches. In conjunction with previous surveys, this project will allow us to understand the demographics of brown dwarf companions to high-mass stars at several orders of magnitudes in separations, from 10 to >1000 AU from these data, which in the next few years we will be able to combine with Gaia detections of brown dwarfs from 1-10 AU around higher mass stars, a regime unprobed by radial velocity surveys, as A stars are not amenable to precision radial velocity observations. By comparing this population of brown dwarf companions to high mass stars to the equivalent population around solar-type stars, we can, for the first time, understand how this low-mass end of the binary population evolves with stellar host mass. Given the limited lifetimes of more massive stars, brown dwarfs that are companions also form a critical set of benchmark brown dwarfs which can be used to calibrate brown dwarf formation and evolution models in a way that the isolated field population cannot.
StatusActive
Effective start/end date1/21/221/20/25

Funding

  • NASA: Shared Services Center (NSSC): $537,787.00

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