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Monitoring of spotted RS CVn and BY Dra type stars. I. Simultaneous optical and infrared photometry
UBV(RI)cJHK photometry of 6 active stars, collected at theSouth African Astronomical Observatory in 1996 and 1997, is presented.The light and colour curves, which are compared with those observed atprevious epochs, show significant variation in their wave-likemodulation and in their maximum brightness.
| Long-term monitoring of active stars. IX. Photometry collected in 1993
As a part of an extensive program focused on the global properties andevolution of active stars, high-precision UBV(RI)_c and UBV photometryof 31 selected stars is presented. The UBV(RI)_c observations werecollected at the European Southern Observatory over the 31 December1992-18 January 1993 and the 20 November-3 December 1993 intervals.Additional UBV photometry obtained by the ``Phoenix" and by the CataniaAstrophysical Observatory Automatic Photoelectric Telescopes from 1990to 1993 is also presented for some of the program stars. Significantevolution of the light curves, period variations and evidence forlong-term variability of the global degree of spottedness are found.Some spectral classifications are revised and the inferred photometricparallaxes are compared, whenever possible, with the values measured bythe Hipparcos satellite. These observations are finalized to theconstruction of an extended photometric database, which can giveimportant clues on topics such as the stability of spotted areas,differential rotation, solar-like cycles and the correlation betweeninhomogeneities at different atmospheric levels. Based on data collectedat the European Southern Observatory, La Silla, Chile. Tables and thecomplete data set are also available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/367/910
| Long-term monitoring of active stars. VIII. UBV(RI)_(c) photometry collected in February 1992
As a part of an extensive program focusing on the global properties andevolution of active stars, high-precision UBV(RI)_c photometry of 31selected stars, collected at the European Southern Observatory over the14-29 February 1992 interval, is presented. Significant evolution of thelight curves, period variations and evidence for long-term variabilityof the global degree of spottedness are found. Some spectralclassifications are revised and the inferred photometric parallaxes arecompared, whenever possible, with the values measured by the Hipparcossatellite. Flare events were detected for the star HD16157 = CC Eri, EXO 055609-3804.4 TY Coland HD 119285 = V851 Cen. Optical variability wasdiscovered for the Pop II binary HD 89499. Theseobservations contribute to the establishment of a time-extendedphotometric database which can give important clues on topics such asthe stability of spotted areas, differential rotation, solar-like cyclesand the correlation between inhomogeneities at different atmosphericlevels. based on data collected at the European Southern Observatory, LaSilla, Chile.
| Long-term monitoring of active stars. V. UBV(RI)_ c_ photometry collected in Feb.-Mar. 1990.
High-precision UBV(RI)_c_ photometry of 12 selected active stars,collected at the European Southern Observatory (La Silla, Chile) overthe period February - March 1990, is presented. Significant evolution ofthe light curves, period variations and, in most cases, evidence forlong-term variability of the global degree of spottedness are found.Some of the spectral classifications are discussed. This paper is partof a more extensive program focusing on the global properties andevolution of active stars and is aimed at establishing a time-extendedphotometric database which can give important clues on topics such asthe stability of the spotted areas, differential rotation and solar-likecycles.
| Long-term monitoring of active stars. II - UBV(RI)c observations at ESO during January-March 1989
In the framework of a research program focusing on the global propertiesand evolution of photospheres and outer atmospheres of active stars, theauthor presents high-precision UBV(RI)c photometry of 15 selected RSCVn, BY Dra, and FK Com-type systems observed at the European SouthernObservatory (La Silla, Chile) in the period January-March 1989.Significant evolution both in amplitude and shape of the wave-like lightcurves is found with respect to previous observations. Evidence forlong-term variability for most of the observed stars is also presented,and some of the spectral classifications are rediscussed.
| Local photometric standards for CaII emission stars
UBV data are given for 108 stars which are suitable local standards for52 stars with strong Ca2 emissions. An additional eight stars wererejected as possible standards because of suspected variability.
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