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		| Paper: | 
		HST/STIS Coronagraphic Imaging of Pre-Main Sequence Stars | 
	 
	
		| Volume: | 
		321, Extrasolar Planets:  Today and Tomorrow | 
	 
	
		| Page: | 
		244 | 
	 
	
		| Authors: | 
		Grady, C.A. | 
	 
	
	
		| Abstract: | 
		We present the results of a coronagraphic imaging survey of millimeter-selected classical T Tauri stars, and optically bright Herbig Ae stars. We find similar frequency of bipolar microjet detections, and similar evolutionary timescales for the optical brightness of disks exterior to 0.5" (50-70 AU at d=100-140 pc). We find an increasing fraction of stars with known large disks which are optically not detected beginning at ≈ 5 Myr. Many of these same stars have previously been identified as having substantial reservoirs of millimeter-sized grains, suggesting that we are detecting the decoupling of the dust from the gas, which is expected to be a necessary precursor for large-scale planetesimal formation. | 
	 
	
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