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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.
| Photometric oscillations and instrumental characteristics. 2: an examination of fast IR photometry of Gliese 897AB
Investigations into the instrumental characteristics of the EuropeanSouthern Observatory (ESO) fast photometer (outlined in Paper 1) arediscussed in relation to data for the red dwarf binary, Gliese 897AB.The K-band data for this star and two comparison stars from 11/12November 1993 at sub-second time resolution were available from the 1meter IR telescope. The photometeric data were searched for intrinsicrapid variations down to 5 Hz. There is no evidence of stellarperiodicity in the range 0.2 s to 10 s sustained for one minute.
| 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.
| Activity in late-type stars. VI - Optical photometry and UV spectroscopy of the active dMe star, FK Aquarii in late 1983
Optical photometry and UV spectroscopy are reported for the flare/BY Drastar FK Aqr from 1983. These data are used to derive the rate of opticalenergy release in U-band flaring and compare it to four previous epochs.No conclusive evidence of any variation in this rate over an 8-yrinterval has been found. No measurable BY Dra variations were present,but a comparison with the mean magnitude in 1979 suggests that spotswere present in 1983, but were uniformly distributed in longitude. Acomparison of transition-region line fluxes with those recorded in 1979does not indicate any large changes, but the chromospheric Mg II lineflux is smaller by about 25 percent.
| Large and kinematically unbiased samples of G- and K-type stars. VI - Evolved stars in the Moore-Paddock-Wayman sample
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1990PASP..102..507E&db_key=AST
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Besorolás csoportokba:
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Pozíciós és asztrometriai adatok
| Csillagkép: | Sas |
| Rektaszcenzió: | 22h35m53.95s |
| Deklináció: | -20°56'05.2" |
| Vizuális fényesség: | 7.552 |
| Távolság: | 291.545 parszek |
| RA sajátmozgás: | 4.5 |
| Dec sajátmozgás: | -21.2 |
| B-T magnitude: | 9.456 |
| V-T magnitude: | 7.71 |
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