0 Assigned ID: 2449 ----- Attempting Submission 1 (Fri Apr 09 23:26:06 GMT 2021) ----- HST Phase I Proposal 2449 successfully submitted. Receipt: # 2449-1 ----- Attempting Submission 2 (Fri Apr 09 23:55:03 GMT 2021) ----- Filling the gap between directly-imaged and RV/transiting planets will test theories of planet formation across the full range of semi-major axes, connecting formation of close to wide separation gas giants and substellar companions. Companions are notoriously hard to image near lambda/D, as coronagraphs and PSF subtraction techniques are best at >>lambda/D. Non-redundant aperture masking interferometry (NRM) can reveal companions at relevant scales, but is severely flux-limited due to the mask. Kernel-phase interferometry (KPI) applies a similar analysis to (archival) unobscured images, treating the full aperture as a grid of interfering subapertures. We have completed a new KPI pipeline for HST/NICMOS and demonstrated it for a binary survey of nearby old brown dwarfs, refining the astrometry of known companions and clarifying past marginal detections. We have also characterized the detection limits, demonstrating significant sensitivity down to flux ratios of ~10^2 at 0.5 lambda/D. If applied to HST imaging of young brown dwarfs, KPI reaches planetary-masses (~3-5 MJup) on Solar-System scales (>6 AU). We therefore propose a KPI search for planetary mass companions (PMCs) in HST/ACS imaging of 34 young BDs and low-mass stars in the young star-forming regions of Taurus and Upper Scorpius. Past (classical) image analysis was only sensitive to wide (>50 au) PMCs, but we will find companions down to ~5 au, an orbital range where young PMCs (e.g. 2M1207b) have been discovered with more classical techniques around the very nearest young BDs. We will also discover 3-5 new binary companions at tight separations which test models of binary formation and young BD evolution. Samuel Factor is a graduate student working with Adam Kraus and has been the primary developer of the kernel-phase pipeline and first author of the demonstration paper (in prep.) analyzing NICMOS observations. Adam Kraus (UT-Austin Associate Professor) is one of the major users of nonredundant aperture-mask interferometry in the community, having led detailed studies of individual high-profile science targets (such as LkCa15) and extensive demographic studies of large samples (such as YSOs, stars in star clusters, and exoplanet host stars from Kepler). Exoplanets and Exoplanet Formation Stellar Physics and Stellar Types 0 Regular false false false false false SUPPORTED