We discuss here the nature of a rich zoo of knots, filaments, jets and jet-like systems, located--in terms of morphology and kinematics--either inside or outside the main nebular bodies of planetary nebulae (PNe). These features are low-ionization structures (LISs) especially prominent in [N II] and other low-ionization line emission, which are

EMIR is a multiobject intermediate resolution near infrared (1.0 - 2.5 microns) spectrograph with image capabilities to be mounted on the Gran Telescopio Canarias (Observatorio del Roque de los Muchachos, La Palma, Spain). EMIR is under design by a consortium of Spanish, French and British institutions, led by the Instituto de Astrofisica de

We study the effect that the temperature structure has on the determination of the primordial helium abundance, Yp. We provide an equation linking T(O III), the temperature derived from the [O III] lines, and T(He II), the temperature of the He I lines, both for H II regions with O++ only and for H II regions where a fraction of O+ is present. By

IAUC 7821 available at Central Bureau for Astronomical Telegrams.

The results of the tenth multi-site campaign of the STEPHI network are reported. The delta 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

We present a general procedure for obtaining the present density fluctuation probability distribution given the statistics of the initial conditions. The main difficulties faced with regard to this problem are those related to the nonlinear evolution of the density fluctuations and those posed by the fact that the fields we are interested in are