{'fraction_non_alphanumeric': 0.047818791946308725, 'fraction_numerical': 0.03313758389261745, 'mean_word_length': 4.184782608695652, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
HIGH RESOLUTION IMAGES OF ORBITAL MOTION IN THE TRAPEZIUM CLUSTER: FIRST SCIENTIFIC RESULTS FROM THE MMT DEFORMABLE SECONDARY MIRROR ADAPTIVE OPTICS SYSTEM

We present the first scientific images obtained with a deformable secondary mirror adaptive optics system. We utilized the 6.5m MMT AO system to produce high-resolution (FWHM=0.07) near infrared (1.6μm) images of the young (∼ 1 Myr) Orion Trapezium θ Ori cluster members. A combination of high spatial resolution and high signal to noise allowed the positions of these stars to be measured to within ∼ 0.003 accuracies. We also present slightly lower resolution (FWHM∼0.085) images from Gemini with the Hokupa’a AO system as well. Including previous speckle data (Weigelt et al. 1999), we analyze a six year baseline of high-resolution observations of this cluster. Over this baseline we are sensitive to relative proper motions of only ∼ 0.002/yr (4.2 km/s at 450 pc). At such sensitivities we detect orbital motion in the very tight θ Ori B2B3 (52 AU separation) and θ 1 Ori A1A2 (94 AU separation) systems. The relative velocity in the θ Ori B2B3 system is 4.2±2.1 km/s. We observe 16.5±5.7 km/s of relative motion in the θ Ori A1A2 system. These velocities are consistent with those independently observed by Schertl et al. (2003) with speckle interferometry, giving us confidence that these very small (∼ 0.002/yr) orbital motions are real. All five members of the θ Ori B system appear likely gravitationally bound (B2B3 is moving at ∼ 1.4 km/s in the plane of the sky w.r.t. B1 where Vesc ∼ 6 km/s for the B group). The very lowest mass member of the θ Ori B system (B4) has K ′ ∼ 11.66 and an estimated mass of ∼ 0.2M⊙. There was very little motion (4±15 km/s) detected of B4 w.r.t B1 or B2, hence B4 is possibly part of the θ Ori B group. We suspect that if this very low mass member is physically associated it most likely is in an unstable (non-hierarchical) orbital position and will soon be ejected from the group. The θ Ori B system appears to be a good example of a star formation “mini-cluster” which may eject the lowest mass members of the cluster in the near future. This “ejection” process could play a major role in the formation of low mass stars and brown dwarfs. Subject headings: instrumentation: adaptive optics — binaries: general — stars: evolution — stars: formation — stars: low-mass, brown dwarfs