No abstract

No abstract

We have obtained FWHM images of HL Tau at K@, H, and J utilizing the University of Hawaii 0A .2 Adaptive Optics System at the 3.6 m CFHT. These are the highest resolution deep images of HL Tau ever obtained in the infrared. They provide unique insight into HL TauÏs circumstellar environment. An active accretion disk is directly resolved around HL Tau for the Ðrst time in the infrared. The physical characteristics of this accretion disk AU, and P.A. D 125¡) are consistent with the inner disk (R D D 150 discovered by submillimeter (0.8 mm) interferometry by Lay et al. (1994), and conÐrmed by 2.7 mm interferometry by Mundy et al. (1996). Bipolar cavities aligned with the accretion disk axis are for the Ðrst time detected in the infrared. We have monitored the upper cavity at comparable angular resolution for three epochs over the last 2 yr. The cavity appears to be expanding at up to D30 km s~1. This cavity is estimated to have been created in an outburst in the direction of the optical jet D100 yr ago.Accurate photometry and astrometry were obtained for the nearby XZ Tau binary and the unre-0A .3 solved HL Tau yr~1 onto a stable accretion disk AU) around a young 0.7 preÈmain-sequence (PMS)We Ðnd that to reproduce the observed SED, the central unresolved source in HL Tau is required to be a very young (D105 yr) PMS star surrounded by an active accretion disk. The large observed extinction from the inclined disk implies an estimated accretion disk mass of D0.04 M _ .

A comparative study is made of the Knox-Thompson and triple-correlation techniques as applied to image restoration. Both photon-noise-degraded imaging and atmospheric-turbulence-degraded imaging are considered. The signal-to-noise ratios of the methods are studied analytically and with the aid of computer simulations. The ability to retain diffraction-limited information on imaging through turbulence is considered in terms of phaseclosure relationships. On the basis of this work it is found that the two image-restoration techniques are effectively equivalent.

No abstract