Cyg OB2 No. 5 (BD+40deg4220; V729 Cyg) is known to be a contact binary system formed by two O-type stars. For this object a 6-cm radio emission has been detected at the optical position as well as an additional weak non-thermal radio source located at ~ 0.9 arcsec to the north east of the contact binary. It has been suggested that this radio

IAUC 6721 available at Central Bureau for Astronomical Telegrams.

A new method of fitting tridimensional power spectra of solar oscillations is described and compared with a previous one whose use has been more common. The new method fits the parameters of the Lorentzian profiles in a bidimensional k - omega diagram constructed from an azimuthal average of the tridimensional one. The horizontal velocities are

Photospheric and chromospheric solar magnetograms sometimes show opposite polarity. This intriguing phenomenon is associated with the emergence of magnetic flux and with nearby, but not necessarily superposed, flaring activity. Despite the fact that there may be different explanations, it is shown here that the observed reversals are consistent

Optical imaging and spectroscopy reveal that the ionised region No.252 in the list of Marsalkowa (1974Ap&SS..27....3M), whose photograph is presented in the ``Atlas of Galactic Nebulae'' by Neckel & Vehrenberg (1990), is actually a planetary nebula. According to Acker et al. (1992ESOPN...1....1A), the object should therefore be named as PN G321.6

In an Omega 0 = 1 universe, within the classical Eulerian theory of gravitational instability, the redshift evolution of a peculiar velocity field in a region with arbitrary initial density contrast is derived, for the first time, in real space and third-order perturbation theory. A vector proportional to the gravitational acceleration can also be