Abstract. Near-infrared observations of line emission from excited H 2 and in the continuum are reported in the direction of the Orion molecular cloud OMC1, using the European Southern Observatory Very Large Telescope UT4, equipped with the NAOS adaptive optics system on the CONICA infrared array camera. Spatial resolution has been achieved at close to the diffraction limit of the telescope (0.08 −0.12 ) and images show a wealth of morphological detail. Structure is not fractal but shows two preferred scale sizes of 2. (1100 AU) and 1.2 (540 AU), where the larger scale may be associated with star formation.

Abstract. The results of the tenth multi-site campaign of the STEPHI network are reported. The δ Scuti stars V624 Tau (HD 23156) and HD 23194, belonging to the Pleiades cluster, were observed photometrically for 34 days on three continents during 1999 November-December. An overall run of 343 hours of data was collected. Seven frequencies for V624 Tau and two frequencies for HD 23194 have been found above a 99% confidence level. These results greatly improve those found in previous studies with much less data. A preliminary comparison of observed and theoretical frequencies suggests that both stars may oscillate with radial and non-radial p modes of radial orders typical among δ Scuti stars.

Abstract. We report here the discovery of very low amplitude oscillations in the Pleiades star HD 23628. The 14-nights high quality light curve designates HD 23628 as a new member of the δ Scuti stars class. Amplitude spectra indicate a multi-periodic pulsation behaviour, and four pulsation frequencies have been detected so far. The frequency distribution suggests the presence of nonradial modes. Pulsation constant values of the four modes are distributed in the range corresponding to fundamental f to p 4 radial modes.