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M.R. Meyer (Steward Observatory), D. Backman (Franklin & Marshall College), E.E. Mamajek (Steward Observatory), V.M. Herrera (Franklin & Marshall College), P. Hinz (Steward Observatory), J.M. Carpenter (Caltech), W. Hoffman (Steward Observatory), J. Hora (Harvard-Smithsonian CfA)
We report the discovery of a young star that appears to have a very unusual distribution of circumstellar dust. HD 113766 is a binary system with a projected separation of 170 AU located at a distance of 130 pc with component stars characterized by F3 and F5 spectral types. Attention has been called to this system since its association with a detection in the IRAS Point Source Catalogue (IRAS 13037-4545). Utilizing data obtained from the HIPPARCOS/TYCHO photometric database, we have estimated the reddening and intrinsic stellar luminosity of each component. Placement of both stars in the H-R diagram suggests an age of 10-20 Myr, consistent with its apparent kinematic membership in the Lower Centarus Crux sub-group of the Sco-Cen OB association. We have obtained mid-IR imaging photometry using the MIRAC/BLINC instrument on the 6.5m Magellan I telescope and resolved for the first time the emission between the binary components. The unresolved excess flux observed at 4.8, 11.7, and 18.0 microns appears to originate from within 20, 50, and 80 AU respectively of the primary star while the infrared emission from the secondary is consistent with that expected from a stellar photosphere within the errors. A simple model of the excess emission from 4.8 through 60 microns suggests a range of blackbody temperatures from approx. 290 to 440 K which is observed to reprocess approx. 10 field. If the disk is devoid of gas, constraints implied by the Poynting-Robertson effect coupled with the estimated age of the system suggest that the dust is being continuously replentished through collisions of planetesimals. The extent of this hypothetical planetesimal belt would be from <= 1.0 to 2.3 AU surrounding this solar-type star, comparable to the position of the asteroid belt in our own solar system.
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