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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
| Rotational modulation and flares on RS CVn and BY Dra stars. XX. Photometry and spectroscopy of CC Eri in late 1989
The active flaring binary CC Eri was studied via multi-wavelengthobservations involving multi-based photometry and ground- andspace-based spectroscopy. Combining early spectroscopic data with thepresent implies an orbital period of P=1.5615 days. Furthermore, thespectroscopic data suggests spectral types of K7 and M3 for the system.The optical photometry indicated a small spot coverage in late 1989,consistent with data taken a year later which showed CC Eri entering itsbrightest-to-date phase. Two flares were detected in the ultravioletspectral data. These flares radiated 2.7 1031 erg and 1.61031 erg in the C Iv line alone, each with a total estimatedradiative energy budget of ~ 1036 erg. For thehigher-temperature lines, such as C Iv, there was no systematicvariability with phase. The lower-temperature lines show a slightindication of rotational modulation. However, there is a much largerscatter in the individual measurements of the Mg Ii and C Iv fluxes thanwould be expected from measurement errors alone, consistent with anatmosphere showing continual small-scale activity.
| 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. VI. UBV(RI)_c observations collected in Sep.-Oct. 1990
In the framework of an extensive program focusing on the globalproperties and evolution of active stars, high-precision UBV(RI)_cphotometry of 9 selected stars, collected at the European SouthernObservatory over the intervals 7-17 September and 30 September - 10October 1990, is presented. Significant evolution of the light curves,period variations and evidence for long-term variability of the globaldegree of spottedness are found. Some of the spectral classificationsare discussed. These observations contribute to the establishment of atime-extended photometric database which can give important clues ontopics such as the stability of the spotted areas, differentialrotation, solar-like cycles and the correlation between inhomogeneitiesat different atmospheric levels. Based on data collected at the EuropeanSouthern Observatory, La Silla, Chile. Tables and the complete data setare also available in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr or via http://cdsweb.u-strasbg.fr/Abstract.html
| Long-term monitoring of active stars. IV. UBV(RI)_c_ observations obtained at La Silla in December 1989.
High-precision UBV(RI)_c_ photometry of 23 selected acitve stars,collected at the European Southern Observatory (La Silla, Chile) overthe period 9-28 December 1989, is presented. This paper is part of alarger program focusing on the global properties and evolution of activestars and is aimed at establishing a time-extended database which cangive important clues on topics such as the stability of the spottedareas, differential rotation and solar-like cycles. Significantevolution of the wave-like light curves, period variations and, in mostcases, evidence for long-term variability of the global degree ofspottedness are found for the observed stars. Some spectralclassifications are rediscussed and evidence for a newly discoveredvariable star is given.
| 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.
| UBVRI observations of southern hemisphere active stars. II - 1987 data
Results are presented on high-precision UBV (RI)c photometricobservations of 13 southern-hemisphere RS CVn, BY Dra, and FK Com-typevariable stars, carried out in December 1987 at the European SouthernObservatory at La Silla (Chile). Compared with previous observations,significant changes of the light curves were detected, both in amplitudeand shape.
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| Сазвежђа: | Еридан |
| Ректацензија: | 02h36m07.42s |
| Deклинација: | -44°45'32.1" |
| Apparent магнитуда: | 8.095 |
| Даљина: | 173.913 parsecs |
| Proper motion RA: | 12.5 |
| Proper motion Dec: | 17.9 |
| B-T magnitude: | 9.212 |
| V-T magnitude: | 8.188 |
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