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Two-colour photometry for 9473 components of close Hipparcos double and multiple stars
Using observations obtained with the Tycho instrument of the ESAHipparcos satellite, a two-colour photometry is produced for componentsof more than 7 000 Hipparcos double and multiple stars with angularseparations 0.1 to 2.5 arcsec. We publish 9473 components of 5173systems with separations above 0.3 arcsec. The majority of them did nothave Tycho photometry in the Hipparcos catalogue. The magnitudes arederived in the Tycho B_T and V_T passbands, similar to the Johnsonpassbands. Photometrically resolved components of the binaries withstatistically significant trigonometric parallaxes can be put on an HRdiagram, the majority of them for the first time. Based on observationsmade with the ESA Hipparcos satellite.
| Period analysis of τ Pegasi and the nature of multiple-periodic δ Scuti stars.
The δ Scuti variable star τ Pegasi was observed with the 60-cmtelescope at Xinglong Station of Beijing Astronomical Observatory from1991 to 1992.. Period analyses were made for the 1991-1992 data set andother avaliable data sets. Two pulsation frequencies (18.40567 and18.0178 cycles/d) with visual amplitudes of 0.0116 and 0.0039mag werefound. The observed frequencies indicate nonradial p_4_ mode with l=1.The long-term variations in phasing of the first period is a value ofdP/dt about 10^-9^. The amplitude of the first frequency increased from0.0067mag (1975-1979) to 0.0116mag (1991-1992). The amplitude of thesecond frequency increased from 0.0018mag (1975-1979) to 0.0039mag(1991-1992). The beating between the two frequencies can fit the1991-1992 data to +/-0.004mag. The number of frequencies detected, thelong-term amplitude variability and the mode identification show thatτ Peg is a typical nonradially pulsating δ Scuti star.
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