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Discovery of two short-period eclipsing binaries with active components.
We present high-precision UBV(RI)_c_ photometry as well as soft X-raylight curves for the visual triple system HD 9770 and the visual binaryHD 195434, obtained at the European Southern Observatory and extractedfrom the ROSAT all-sky survey, respectively. The optical photometryrevealed that in both systems one component is a very short-periodeclipsing binary showing also BY Dra-type variability. We have computedaccurate orbital periods, deduced approximate physical parameters,spectral classifications, distances and X-ray luminosities andidentified which component of each visual system is responsible for theoptical variability. Futhermore, we find that both systems are variablein X-rays, but no correlation with the optical variability is seen.
| UBV(RI)c photometry of equatorial standard stars - A direct comparison between the northern and southern systems
UBV(RI)c photometry of 212 stars from Landolt's list of equatorialstandards is presented. The observations are tied to the system definedby Cousin's E-region standards. A comparison of the present results withLandolt's reveals reasonably good agreement for (V-R)c and (V-I)c, butmarked systematic differences for (B-V) and (U-B). The UBV systems ofCousins and Landolt are evidently not the same and both probably differfrom Johnson's original system.
| Photoelectric Photometry of Stars in the Vilnius System in Kapteyn Areas SA:92 SA:108 and SA:112
Not Available
| UBVRI photometric standard stars around the celestial equator
It is pointed out that accurate, internally consistent, and readilyaccessible standard star photometric sequences are necessary for thecalibration of the intensity and color data which astronomers obtain atthe telescope. The photometric results provided in connection with thepresent study represent the first part of an effort which is concernedwith the presentation of UBVRI photoelectric photometric standard starsin the magnitude range from 7 to 17 over as broad a range in color aspossible. All of the photometric observations were made with a 31034type photomultiplier used in a pulse counting mode. Some 15 to 25standard stars chosen from Cousins' lists (1973, 1976) in the E-regionswere observed with an 0.4-m telescope each night along with the programstars. UBVRI standard stars were observed periodically throughout thenight. Observations with a 0.9-m telescope were also conducted. TheUBVRI photoelectric observations take into account 223 stars.
| Photoelectric Observations of Stars near Northern Hemisphere Selected Areas
Not Available
| Lichtelektrische UBV-Photometrie von Standardsternen und in vier Sternfeldern am Äquator
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Observation and Astrometry data
| Constellation: | Αετός |
| Right ascension: | 20h38m16.45s |
| Declination: | +01°00'59.4" |
| Apparent magnitude: | 7.892 |
| Proper motion RA: | 11.1 |
| Proper motion Dec: | -2 |
| B-T magnitude: | 10.01 |
| V-T magnitude: | 8.067 |
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