From Stardust to Planetesimals: Contributed Papers - NASA Lunar ...

PLANETESIMALS AROUND V536 AQLN. AGEORGES ESO, Karl-Schwarzschild-Straj3e 2, D-85718 Garching,GermanyW. J. DUSCHL ITA, Heidelberg & MPIfR, Bonn, Germany1. INTRODUCTIONThe pre-main sequence star V536 Aql, classified as a K7 classical T Tauri star byCohen & Kuhi (1979) has been resolved, by high angular resolution near-infraredspeckle observations, as a close binary (0.52" separation at 17) surrounded by extendedstructures (Ageorges et al. 1994). These structures seen, both in the July1993 and April 1994 observations, are not at the same position in the reconstructedimage (Fig. 2) and do not present exactly the same shape at both times. Altough itis unlikely that the presence of these structures is due to seeing calibration problems,the exact shape might be affected by it. We cannot presently make a final interpretationof the observations but can formulate different possibilities: the `circumstellar'material seen in our images can be an independent cloud, or simply gas or dust, infront of the system on our line of sight, but close enough to still be illuminated bythe binary; this material may be `by chance' there or be a remnant of the material inwhich the star was born.We propose a model to explain the position variation of the extended structures.New observations are under reduction and should help to determine the exact valueof this motion. At their distance from the star, motions of the extended matterwould correspond to velocities much higher than the Kepler velocities. To explainthis., we have developed a model based on a `torch-light' effect. The possibility thatthe observed elongated structures belong to a circumstellar or circumbinary disk arealso discussed below.2. OBSERVATIONSNear-infrared observationsThe observations were done with the near-infrared speckle camera SHARP (Systemfor High Angular Resolution Pictures, Hofmann et al. 1995) installed at the ESO NTT(3.5 m telescope equipped with an active optic system). The detector of SHARP isa NICMOS 3, 256 x 256 pixels corresponding to a 12.8 2" field of view. The datawere analysed using the MPE speckle reduction software package (Eckart & Duhoux1990). We kept the frames obtained under the best similar seeing conditions forboth the source and the reference (SAO 105091, used as point spread function todeconvolve the target source data), to accumulate both simple shift-and-add (SSA)images (Christou 1991) and power spectra. Images in all wavebands were obtained