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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
| A major optical flare on the recently discovered X-ray active dMe star G 102-21.
During the course of UBV photoelectric measurements made at the CataniaAstrophysical Observatory we have observed an unusually intense opticalflare on the nearby M dwarf G 102-21, the optical counterpart of astrong X-ray source recently detected by ROSAT. The amplitude of themagnitude increase ({DELTA}U~7.3mag) and the total energy release in theUBV bands (E_UBV_~(1.4+/-0.3)x10^35^erg) put this event among thestrongest flares ever detected on UV Ceti-type stars. The U-B and B-Vcolours of the flare emission did not significantly change during mostof the flare development. While the B-V is quite a typical colour forstellar flares, the U-B is much bluer when compared with typical valuesgiven in literature. This unusually strong ultraviolet component of theflare emission, together with the very fast flare decay, suggest apossible flare site close to the limb. We find that the observed amountof flare energy could be explained by the fast release of energy storedin a magnetic filament located in between the two G 102-21 stellarcomponents, with a surface magnetic field >=3600G. Thecharacteristics of the quiescent optical emission are also discussed.
| 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.
| HD 37824: a New Variable Star
Not Available
| Proper motions of 650 bright B-type stars.
Not Available
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Посматрања и Астрометриски подаци
| Сазвежђа: | Орион |
| Ректацензија: | 05h40m54.25s |
| Deклинација: | +04°09'42.3" |
| Apparent магнитуда: | 8.205 |
| Proper motion RA: | -20 |
| Proper motion Dec: | 0.1 |
| B-T magnitude: | 9.534 |
| V-T magnitude: | 8.315 |
Каталог и designations:
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