A High-Contrast Imaging Survey ofSIM LitePlanet Search Targets

Abstract

With the development of extreme high contrast ground-based adaptive optics instruments and space missions aimed at detecting and characterizing Jupiter-and terrestrial-mass planets, it is critical that each target star be thoroughly vetted to determine whether it is a viable target given both the instrumental design and scientific goals of the program. With this in mind, we have conducted a high contrast imaging survey of mature AFGKM stars with the PALAO/PHARO instrument on the Palomar 200 inch telescope. The survey reached sensitivities sufficient to detect brown dwarf companions at separations of > 50 AU. The results of this survey will be utilized both by future direct imaging projects such as GPI, SPHERE and P1640 and indirect detection missions such as SIM Lite. Out of 84 targets, all but one have no close-in (0.45-1 ′′ ) companions and 64 (76%) have no stars at all within the 25 ′′ field-of-view. The sensitivity contrasts in the K s passband ranged from 4.5 to 10 for this set of observations. These stars were selected as the best nearby targets for habitable planet searches owing to their long-lived habitable zones (> 1 billion years). We report two stars, GJ 454 and GJ 1020, with previously unpublished proper motion companions. In both cases, the companions are stellar in nature and are most likely M dwarfs based on their absolute magnitudes and colors. Based on our mass sensitivities and level of completeness, we can place an upper limit of ∼17% on the presence of brown dwarf companions with masses >40 M J at separations of >1 arcsecond. We also discuss the importance of including statistics on those stars with no detected companions in their field of view for the sake of future companion searches and an overall understanding of the population of low-mass objects around nearby stars.

Stellar Multiplicity

“…Multiple surveys have addressed the existence of the BD desert among visual companions in both star-forming regions and nearby associations (e.g., Evans et al 2012;Kouwenhoven, Brown & Kaper 2007a;Tanner et al 2007). These survey generally found that BD companions are rare but not absent (e.g., Janson et al 2012b, Nielsen et al 2012).…”

The HADES RV Programme with HARPS-N at TNG

“…Moreover, several high-contrast imaging surveys ruled out the presence of additional co-moving stellar objects close to Gl15A: van Buren et al (1998) excluded the possibility of objects with M > 0.084 M at separations of 9−36 AU, while Tanner et al (2010) ruled out objects up to a magnitude contrast of ∆K s 6.95 mag within 1 (3.57 AU) and ∆K s 10.24 mag within 5 (17.8 AU).…”

Nii: a Bayesian orbit retrieval code applied to differential astrometry

“…Using narrow-angle astrometric observations, such space-based instruments can differentially detect the reflex motion of the target star due to the presence of its planets with very high accuracy (Catanzarite et al 2007;Unwin et al 2008;Goullioud et al 2008). Historically, a series of space missions have been proposed to search for exoplanets using differential astrometry; examples include the Space Interferometry Mission PlanetQuest (SIM PlanetQuest) (Catanzarite et al 2007;Unwin et al 2008;Tanner, Gelino, & Law 2010), the Nearby Earth Astrometric Telescope (NEAT) mission (Malbet et al 2012) and the Search for Terrestrial Exo-Planets (STEP) mission (Chen, Wu, & Li 2013;Liu, Liu, & Zhu 2018). Several follow-up successions of these projects are in progress, namely, the Theia Space Observatory (Malbet et al 2016;The Theia Collaboration et al 2017), the Habitable ExoPlanet Survey (HEPS) mission (Yu et al 2019) and the Closeby Habitable Exoplanet Survey (CHES) mission (Ji & Wang 2020).…”