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A supermaximum of VW Hydri was observed at the ESO site from Oct. 26 until Nov. 9» 1978. High time resolution polarimetrie and spectroscopic measurements have been obtained. This paper reports on some preliminary results.

We have started a project to investigate the connection of post‐novae with the population of cataclysmic variables (CVs). Our first steps in this concern improving the sample of known post‐novae and their properties. Here we present the recovery and/or confirmation of the old novae MT Cen, V812 Cen, V655 CrA, IL Nor, V2109 Oph, V909 Sgr, V2572 Sgr and V728 Sco. Principal photometric and spectroscopic properties of these systems are discussed. We find that V909 Sgr is a probable magnetic CV, and that V728 Sco is a high‐inclination system. We furthermore suggest that the two candidate novae V734 Sco and V1310 Sgr have been misclassified and instead are Mira variables.

Context. Post-common-envelope binaries (PCEBs) consisting of a white dwarf (WD) and a main-sequence secondary star are ideal systems to constrain models of common-envelope (CE) evolution. Until very recently, observed samples of PCEBs have been too small to fully explore this potential, however the recently identified large and relatively homogenous sample of PCEBs from the Sloan Digital Sky Survey (SDSS) has significantly changed this situation. Aims. We here analyze the orbital period distributions of PCEBs containing He-and C/O-core WDs separately and investigate whether the orbital period of PCEBs is related to the masses of their stellar components. Methods. We performed standard statistical tests to compare the orbital period distributions and to determine the confidence levels of possible relations. Results. The orbital periods of PCEBs containing He-core WDs are significantly shorter than those of PCEBs containing C/O-core WDs. While the He-core PCEB orbital period distribution has a median value of P orb ∼ 0.28 d, the median orbital period for PCEBs containing C/O-core WDs is P orb ∼ 0.57 d. We also find that systems containing more massive secondaries have longer post-CE orbital periods, in contradiction to recent predictions. Conclusions. Our observational results provide new constraints on theories of CE evolution. However we suggest future binary population models to take selection effects into account that still affect the current observed PCEB sample.

Context. In 2010 a substellar companion to the solar analog pre-main sequence star PZ Tel and member of the approximately 12 Myr old β Pic moving group was found by high-contrast direct imaging independently by two teams. Aims. In order to determine the basic parameters of this companion more precisely and independent of evolutionary models, hence age-independent, we obtained follow-up spectroscopic observations of the primary and companion. Methods. We used the Spectrograph for INtegral Field Observations in the Near Infrared (SINFONI) at the Very Large Telescope Unit 4/Yepun of ESO's Paranal Observatory in the H + K band and processed the data using the spectral deconvolution technique. The resulting spectrum of the companion was then compared to a grid of Drift-Phoenix synthetic model spectra, a combination of a general-purpose model atmosphere code with a non-equilibrium, stationary cloud and dust model, using a χ 2 minimization analysis. Results. We find a best fitting spectral type of G6.5 for PZ Tel A. The extracted spectrum of the substellar companion, at a spatial position compatible with earlier orbit estimates, yields a temperature T eff = 2500 +138 −115 K, a visual extinction A V = 0.53 +0.84 −0.53 mag, a surface gravity of log g = 3.50 +0.51 −0.30 dex, and a metallicity at the edge of the grid of [M/H] = 0.30 −0.30 dex. Conclusions. We derive a luminosity of log(L bol /L ) = −2.66 +0.06 −0.08 , a radius of R = 2.42 +0.28 −0.34 R Jup , and a mass of M = 7.5 +16.9 −4.3 M Jup for the PZ Tel companion, which is consistent with most earlier estimates using photometry alone. Combining our results with evolutionary models, we find a best-fitting mass of about 21 Jupiter masses at an age corresponding to the recently determined lithium depletion age of 7 +4 −2 Myr. Hence, the PZ Tel companion is most likely a wide brown dwarf companion in the 12 +8 −4 Myr old β Pic moving group.