Large Adaptive optics Survey for Substellar Objects (LASSO) at wide separations around young, nearby, low-mass stars with Robo-AO
Creators: name: Salama, Maissa
name: Ou, James
name: Baranec, Christoph
name: Liu, Michael C.
name: Bowler, Brendan P.
name: Barnes, Paul
name: Bonnet, Morgan
name: Chun, Mark
name: Duev, Dmitry
name: Goebel, Sean
name: Hall, Don
name: Jacobson, Shane
name: Jensen-Clem, Rebecca
name: Law, Nicholas M.
name: Lockhart, Charles
name: Riddle, Reed
name: Situ, Heather
name: Warmbier, Eric
Publisher: name: Zenodo
Year: 2021
Subjects: Very low mass stars
Binaries
High angular resolution imaging
Surveys
Brown dwarfs

description: The purpose of the Large Adaptive optics Survey for Substellar Objects (LASSO) is to directly image new substellar companions (&lt;70 M<sub>Jup</sub>) at wide orbital separations (\(\gtrsim\)50 AU) around young (\(\lesssim\)300 Myrs), nearby (&lt;100 pc), low-mass (0.1-0.8 M<sub>Sun</sub>) stars. We report on 427 young stars imaged in the visible (i') and near-infrared (J or H) simultaneously with Robo-AO on the Kitt Peak 2.1-m telescope and later the Maunakea UH 2.2-m telescope. To undertake the observations, we commissioned a new infrared camera on Robo-AO that uses a low-noise high-speed SAPHIRA detector. We detected 122 companion candidates around 110 stars, of which 58 companions are physically associated based on Gaia DR2 parallaxes and proper motions, another 52 require follow-up observations to confirm physical association, and 12 are background objects. The majority of confirmed and pending candidates are stellar companions, with ~5 being potentially substellar and requiring follow-up observations for confirmation. We also detected a 43\(\pm\)9 M<sub>Jup</sub> and an 81\(\pm\)5 M<sub>Jup</sub> companion that were previously reported. The companion separations range from 2-1112 AU and reach contrast ratios of 7.7 magnitudes in the near infrared compared to the primary. We found 34 of our targets have acceleration measurements derived from Hipparcos-Gaia proper motions. Of those, 58% of the 12 stars with companion candidates have significant accelerations (\(\chi\)<sup>2</sup> &gt;11.8), while only 23% of the remaining 22 stars with no detected companion have significant accelerations. The significance of the acceleration decreases with increasing companion separation. These young accelerating low-mass stars with companions will eventually yield dynamical masses with future orbit monitoring.
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