High Resolution Images of Orbital Motion in the Trapezium Cluster: First Scientific Results from the MMT Deformable Secondary Mirror Adaptive Optics System

Abstract

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 (1.6 um) images of the young (~1 Myr) Orion Trapezium theta 1 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. 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 theta 1 Ori B2B3 (52 AU separation) and theta 1 Ori A1A2 (94 AU separation) systems. Such motions 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 theta 1 Ori B system appear likely gravitationally bound. The very lowest mass member of the theta 1 Ori B system (B4) has K' ~11.66 and an estimated mass of ~0.2 Msun. 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 theta 1 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 theta 1 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.

arXiv commentTo appear in the December 10, 2003 issue of the Astrophysical Journal 21 pages, 14 figures (some in color, but print OK in B&W)

References in corpus (15)

• The Formation of Brown Dwarfs as Ejected Stellar Embryos
• Binarity in Brown Dwarfs: T Dwarf Binaries Discovered with the Hubble Space Telescope WPFC2
• The Formation Mechanism of Brown Dwarfs
• Analysis of isoplanatic high resolution stellar fields by Starfinder code
• Detection of Nine M8.0-L0.5 Binaries: The Very Low Mass Binary Population and its Implications for Brown Dwarf and VLM Star Formation
• Constraints on the Stellar/Sub-stellar Mass Function in the Inner Orion Nebula Cluster
• Multiplicity of Nearby Free-floating Ultra-cool Dwarfs: a HST-WFPC2 search for companions
• A search for L dwarf binary systems
• Hubble Space Telescope Observations of Binary Very-Low-Mass Stars and Brown Dwarfs
• Hokupa'a-Gemini Discovery of Two Ultracool Companions to the Young Star HD 130948
• An Adaptive Optics Survey of M8-M9 Stars: Discovery of 4 Very Low mass Binaries With at Least One System Containing a Brown Dwarf Companion
• Discovery of a 0.15" Binary Brown Dwarf 2MASSJ 1426316+155701 With Gemini/Hokupa'a Adaptive Optics
• A Near-Infrared Wide-Field Proper Motion Search for Brown Dwarfs
• Eccentricity generation in hierarchical triple systems with coplanar and initially circular orbits
• Mid-Infrared Imaging of the Post-AGB Star AC Herculis with the MMT Adaptive Optics System

Cited by in corpus (10)

• Monitoring the Large Proper Motions of Radio Sources in the Orion BN/KL Region
• Diffraction-limited Visible Light Images of Orion Trapezium Cluster With the Magellan Adaptive Secondary AO System (MagAO)
• High Resolution Images of Orbital Motion in the Orion Trapezium Cluster with the LBT Adaptive Optics System
• Multiple Star Systems in the Orion Nebula
• Low-Mass Runaway Stars from the Orion Trapezium Cluster
• Dramatic Evolution of the Disk-Shaped Secondary in the Orion Trapezium Star Theta1 Ori B1 (BM Ori): MOST Satellite Observations
• The prospects for finding brown dwarfs in eclipsing binary systems and measuring brown dwarf properties
• Star Formation, Massive Stars, and Super Star Clusters in Nearby Galaxies with the SKA
• The Intricate Structure of HH 508, the Brightest Microjet in the Orion Nebula
• Gould's Belt to Starburst Galaxies: The IMF of Extreme Star Formation