Tan Hui-song

Photometry of an active Algol-type binary HP Aur

The short period Algol-type binary HP Aur has been studied on the basis ofUBV photometric observations. Its colour indexes were found to be (U-B)=0.14, (B-V)=0.70, and light curves show non-symmetrical and obvious photometric disturbances. Autoregressive spectral analysis and harmonic analysis for its light variations were made. The results indicate its brightness variations have the multiplet quasi-periods and low amplitudes. Its photometric solutions have been obtained using the Wilson-Devinney method. Its mass ratio is 0.5631, orbital inclination is 85.0 and it is a detached system. Its basic model has been discussed briefly.

Observation and study of the H-alpha emission of 33 RS CVN stars

Abstract In September 1984, using the Reticon on the 2.1m telescope of McDonald Observatory, we observed the spectra in the Hα region of 33 binaries of the RS CVn type. Our observations of radial velocity and equivalent width are given here. For the first time, we detected Hα emission in the 3 systems, HD 8357, HD 175742 and HR 7428, and their emission features are described in detail. We also found HD 8357 to have a double spectrum and determined the radial velocity curves of the two components, and their mass ratio. The 6 systems, λ And, UX Ari, RT Lac, AR Lac, HK Lac and HD 185151 show persistent or occasional strong Hα emission, and they are briefly described and analysed. The remaining 24 systems showed absorption features in their Hα profile, but their equivalent widths are appreciably smaller than standard stars of similar spectral type, and they also varied in time. We believe that Hα emission is one of the common features of binaries of this type.

The H-alpha variations of Epsilon Aurigae from the second to the fourth contact

Abstract Epsilon Aurigae was observed in Mar., Aug., 1983 and Jan., Mar., 1984 with Reticon at coude focus of the McDonald 2.7m and 2.1m telescopes. Fifty-six observations were taken over eight nights during 2nd to 4th contact. The Hα shows noticeable variations in profile, radial velocity, and equivalent width of both absorption and emission components. A similar phenomenon was detected during the corresponding phase of the 1955 – 1957 eclipse. A model is proposed, in which the primary is a FO supergiant surrounded by a thin ring (or disk) of radius R = 450 R ⊙ and rotating at velocity V sini = 60 – 70 kms −1 . This is the major source of the Hα emission component. The secondary is a type B star surrounded by a very extended envelope ( R = 1000 R ⊙ ) and its rotational speed is similar to that of the ring of the primary. The B star heats a portion of the envelope comparable in size with the primary with enough hydrogen atoms in the lowest excited states, which cause the absorption of the emission from the primary.

Measurement of the radial velocity of 32 Cygni during its 1981 eclipse

Abstract We photographed the spectrum of 32 Cygni during its 1981 eclipse at the various phases of atmospheric, partial and total eclipses and derived the variation of the radial velocity of the K supergiant component with phase. Different lines of the same multiplet on the same plate showed different radial velocities and there is a hint that short time scale pulses may exist on the K supergiant. A preliminary analysis and discussion is given.

Outside-eclipse H-alpha spectra of five eclipsing binaries

Abstract H∞ region spectra for five binary systems ϵ Aur, ζ Aur, 31 Cyg, 32 Cyg and 22 Vul, were obtained using the 1m refractor coude spectrograph of Yunnan Observatory and the 2.1m coude Reticon of McDonald Observatory, with a dispersion of about 9 A/mm in both cases. All observations were taken outside eclipse. After reduction we obtained the equivalent widths and radial velocities of the H∞ line. Short time scale variations in the H∞ emission were shown in ϵ Aur. The profiles of 31 Cyg and 32 Cyg were found to be very similar.

Photometric study of the eclipsing binary IU Aurigae

Abstract New UBV photometric observations of IU Aur were made at McDonald Observatory in December 1984 and January 1985, showing that the eclipse depth had kept on increasing and the light minimum time had shown periodic changes. Orbital elements were obtained using the Wilson-Devinney method. The inclination is now close to 90°. The continuous variation of inclination over the last few decades suggests the presence of a third body. Absolute parameters of IU Aur were calculated with the help of Mammanos spectral data.

Rotational measurement and study of RS CVn binaries. II

Abstract For 37 components belonging to 31 RS CVn binary systems, we measured the rotation using Reticon data on the 2.1 McDonald Reflector. Combining our previous data for 38 components, we made a statistical analysis on the question of synchronous rotation. Our results show that, while the great majority show synchronous rotation, exceptions are found in all period groups, contradicting the generally held view that all short period and normal period RS CVn stars have synchronous rotation and all long period ones do not.

Observational study of Hα in 31 RS CVn binary systems

Abstract 90 spectral observations of the Hα regions of 31 RS CVn stars made with Reticon on the 2.1 metre McDonald Reflector in 1984 are reported here. Quantitative measurements were made on the Hα emission and absorption components. Combining with our previous observations in [1], we have now observed 70% of the systems in Halls catalogue. On the basis of the combined data, a statistical discussion is presented.