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New findings based on long-term photometric observations of the eclipsing binary V471 Tauri
The post-common envelope and pre-cataclysmic binary V471 Tau has beenobserved by the authors since 1973. At least a complete light curve in Band V bands and more than two eclipse timings were obtained in eachyear. All the available data published so far (including the authors')have been collected and analysed for the brightness and orbital periodchanges. The system brightened about 0.22 mag in both B and V bands moreor less regularly up to 1997 and started to decrease afterwards. Asearch for periodicity of this variation yields a period longer than 85yr. In addition to this long-period variation, a small amplitude ofabout 0.08 mag and short time-interval fluctuations on the meanbrightness have been detected. The variations of the mean brightnesshave been discussed and plausible causes suggested. The changes of theapparent period have been attributed to a third body. Analysis of allthe `observed-calculated' (O-C) data yields a period of 32.4 yr, with asemi-amplitude of 151 s and an eccentricity of 0.30 for the third-bodyorbit. For orbital inclinations greater than 34° the mass of thethird body would possibly match to a brown dwarf. One of the mostinteresting features in the light curve of V471 Tau is the decrement ofthe eclipse depth with time. The depth of the eclipse in the B band hasbeen decreased from 0.082 to 0.057 mag over 34 yr. Subtracting thevariation of the depth due to the brightening of the red dwarf star, theactual variation in depth, originated from from the white dwarf, wasfound to be about 0.012 mag. This change in the brightness of thecompact object has been attributed to the mass accretion from itsprimary component via thermally driven wind and/or flare-like events.
| The Henry Draper Extension Charts: A catalogue of accurate positions, proper motions, magnitudes and spectral types of 86933 stars
The Henry Draper Extension Charts (HDEC), published in the form offinding charts, provide spectral classification for some 87000 starsmostly between 10th and 11th magnitude. This data, being highlyvaluable, as yet was practically unusable for modern computer-basedastronomy. An earlier pilot project (Roeser et al. 1991) demonstrated apossibility to convert this into a star catalogue, using measurements ofcartesian coordinates of stars on the charts and positions of theAstrographic Catalogue (AC) for subsequent identification. We presenthere a final HDEC catalogue comprising accurate positions, propermotions, magnitudes and spectral classes for 86933 stars of the HenryDraper Extension Charts.
| B-V photoelectric photometry of white-dwarf eclipsing binary V471 Tauri
Photoelectric photometry of the unusual binary system, whose light curveshows peculiar light variations, has been done in the two colours. Theobservations obtained at the Ege University Observatory between 1973 and1978 and at the Kottamia Observatory in November 1977 show a variablelight curve. The observed variations in the light curve show a migratingwave towards a decreasing orbital phase similar to those observed in RSCVn-binaries. The migration period appears to be about 191 days. Thetimes of minima indicate that there has been a decrease on the orbitalperiod of the system. However, since there is not enough material on theobserved times of minima, we cannot explain whether the decrease in theorbital period has been sudden or gradual. The radii of the componentshave been computed from the primary minimum alone. With the availablespectroscopic data, the absolute dimensions of the components are alsopresented. It appears to be difficult to explain the evolution of thesystem without taking into consideration the mass loss. The proposedmodels for the evolution of the system and an explanation of theobserved light variations are also presented
| New Observations of the White Dwarf Eclipsing Binary V471 Tauri
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Наблюдательные данные и астрометрия
| Созвездие: | Телец |
| Прямое восхождение: | 03h53m33.50s |
| Склонение: | +16°41'35.9" |
| Видимая звёздная величина: | 9.928 |
| Собственное движение RA: | 66.1 |
| Собственное движение Dec: | -50.7 |
| B-T magnitude: | 10.814 |
| V-T magnitude: | 10.002 |
Каталоги и обозначения:
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