The final dynamical evolution of a cluster is strongly influenced by the removal of the parent gas cloud after the star formation process in the region has stopped. The knowledge of a number of essential physical parameters of young open clusters and associations, such as the mass and velocity distribution of the stars and the gas as a function of position in the cluster, is of vital importance for the construction of detailed dynamical models of these regions. In this context, NGC 2244 has been selected for an observational study. We present our first results, including progress made on membership determination and detection of Hα emission B-type
stars .
The eclipsing binary SV Cam shows photometric features that suggest its membership to the RS CVn group. The existing light curves (covering the period 1947-1986) have been analyzed in order to isolate the contribution of the vave-like distortion; all the observations support the presence of an activity cycle, with a duration of about 10 years. By suppressing the contribution due to the stellar activity, we have derived an "average" light curve, cleaned from the effects due to the spots; this light curve has been analyzed by means of the Wood Computer code in order to get the physical parameters of the system.
Fotometrie [1-3] historicky náleží k části optiky věnované zkoumání světla z hlediska jeho účinku na lidské oko. K popisu tohoto působení proto zavádíme fotometrické veličiny, mezi které řadíme např. svítivost, světelný tok nebo osvětlení. Nejdříve se podíváme na základní jednotku SI svítivost, od níž si odvodíme další fotometrické veličiny. Závěrem si ukážeme fotometrii na příkladu našeho Slunce a různé metody fotometrie v astrofyzice., Photometry historically belongs to the part of optics which examines the effects of radiation on the human eye. To describe these effects we introduce photometric quantities amongst which are luminosity, luminous flux or illumination. First, we focus on the SI base unit luminosisty from which we deduce other photometric quantities. We show how our Sun emits energy and discuss different photometric methods used in astrophysics., Jan Janík., and Obsahuje seznam literatury
Photometric light curves of TW Cas do not exhibit any apparent complications. Yet, a careful analysis of the light conditions in the system leads to some contradictory results. A nontraditional explanation is suggested.