An analysis of the optical flashes produced by Leonid meteoroids impacting the Moon in 1999 November is carried out in order to estimate the fraction of kinetic energy converted into radiation, the so-called luminous efficiency η. It is shown that the observational data are consistent with luminous efficiencies of 2×10-3 in the wavelength range of

We present images and high-resolution spectra of the planetary nebulae IC 2553 and NGC 5882. Spatiokinematic modeling of the nebulae shows that they are composed of a markedly elongated inner shell and of a less aspherical outer shell expanding at a considerably higher velocity than the inner one. Embedded in the outer shells of both nebulae are

File table1.dat contains near-infrared JHK magnitudes of a sample of 18 Vega-like and post-T Tauri stars observed by the EXPORT collaboration. File table2.dat contains near-infrared JHK magnitudes of a sample of 4 pre-main sequence stars observed by EXPORT. The data were taken during four observing runs in the period May 1998 to January 1999. (3

IAUC 7506 available at Central Bureau for Astronomical Telegrams.

We present intensive optical, infrared, and radio monitoring observations of the BL Lac object OJ 287, taken between the years 1993-1998. Two large optical outbursts were detected at the predicted times in November 1994 and December 1995. The detection of these outbursts supports the binary black hole model for OJ 287. Optical and radio

We simulate the characteristics of the Galactic population of radio and gamma-ray pulsars using Monte Carlo techniques. At birth, neutron stars are spatially distributed with supernova-kick velocities in the Galactic disk and randomly dispersed in age back to 109 years. They are evolved in the Galactic gravitational potential to the present time