skip to main content

SciTech ConnectSciTech Connect

Title: DIFFRACTION-LIMITED VISIBLE LIGHT IMAGES OF ORION TRAPEZIUM CLUSTER WITH THE MAGELLAN ADAPTIVE SECONDARY ADAPTIVE OPTICS SYSTEM (MagAO)

We utilized the new high-order (250-378 mode) Magellan Adaptive Optics system (MagAO) to obtain very high spatial resolution observations in ''visible light'' with MagAO's VisAO CCD camera. In the good-median seeing conditions of Magellan (0.''5-0.''7), we find MagAO delivers individual short exposure images as good as 19 mas optical resolution. Due to telescope vibrations, long exposure (60 s) r' (0.63 {mu}m) images are slightly coarser at FWHM = 23-29 mas (Strehl {approx}28%) with bright (R < 9 mag) guide stars. These are the highest resolution filled-aperture images published to date. Images of the young ({approx}1 Myr) Orion Trapezium {theta}{sup 1} Ori A, B, and C cluster members were obtained with VisAO. In particular, the 32 mas binary {theta}{sup 1} Ori C{sub 1} C{sub 2} was easily resolved in non-interferometric images for the first time. The relative positions of the bright trapezium binary stars were measured with {approx}0.6-5 mas accuracy. We are now sensitive to relative proper motions of just {approx}0.2 mas yr{sup -1} ({approx}0.4 km s{sup -1} at 414 pc)-this is a {approx}2-10 Multiplication-Sign improvement in orbital velocity accuracy compared to previous efforts. For the first time, we see clear motion of the barycenter of {theta}{sup 1} Ori B{sub 2}more » B{sub 3} about {theta}{sup 1} Ori B{sub 1}. All five members of the {theta}{sup 1} Ori B system appear likely to be a gravitationally bound ''mini cluster'', but we find that not all the orbits can be both circular and co-planar. The lowest mass member of the {theta}{sup 1} Ori B system (B{sub 4}; mass {approx}0.2 M{sub Sun }) has a very clearly detected motion (at 4.1 {+-} 1.3 km s{sup -1}; correlation = 99.9%) w.r.t. B{sub 1}. Previous work has suggested that B{sub 4} and B{sub 3} are on long-term unstable orbits and will be ejected from this ''mini cluster''. However, our new ''baseline'' model of the {theta}{sup 1} Ori B system suggests a more hierarchical system than previously thought, and so the ejection of B{sub 4} may not occur for many orbits, and B{sub 3} may be stable against ejection in the long-term. This ''ejection'' process of the lowest mass member of a ''mini cluster'' could play a major role in the formation of low-mass stars and brown dwarfs.« less
Authors:
; ; ; ; ; ; ;  [1] ; ; ; ; ; ;  [2] ; ;  [3]
  1. Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States)
  2. INAF-Osservatorio Astrofisico di Arcetri, I-50125, Firenze (Italy)
  3. Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)
Publication Date:
OSTI Identifier:
22133911
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 774; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCURACY; BINARY STARS; CAMERAS; CHARGE-COUPLED DEVICES; DIFFRACTION; IMAGES; MASS; OPTICAL SYSTEMS; ORBITS; PROPER MOTION; SPATIAL RESOLUTION; STAR EVOLUTION; TELESCOPES; VELOCITY