Liu Xue-fu

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.

Light fluctuation and changes in the orbital period of the close binary 44 i Boo

Abstract We present the result of UBV photometry and narrow-band photoelectric photometry of 44 i Boo made in January 1980 and March 1982, and we analysed the change in the orbital period of the binary over the past 65 years. We think that the fluctuations in the light curve are related to surface activities (cool and hot spots) on the stars and gas motion between the two stars, that the slowly-changing term in the orbital period is due to the light-time effect, while sudden changes in the period are related to mass ejection and eruptions on the stars.

The radial velocity of zeta aurigae during its 1979/80 eclipse

Using spectrographic plates obtained on 11 nights during its 1979/1980 eclipse, we have obtained a radial velocity curve of ζ Aur. Our results are in general agreements with previous measurements, but we note that the radial velocity just before the total eclipse showed an appreaciable decrease. A preliminary discussion is made.

New hα survey of chromospherically active binaries

We have obtained CCD spectra for 30 chromospherically active binaries using the 2.16 m telescope at Beijing Observatory in 1995. Our purpose was to search for the presence ofHα emission which is characteristic of stars with extreme levels of chromospheric activity. Spectra of V711 Tau, V471 Tau, HD 12545 and V833 Tau presentedHα emission above the continuum in the different degree. TheHα behavior of the other observed 26 active binaries, which were unknown in CABS (1993), has been discovered in this paper. TheHα profiles of the most among 26 systems are partially filled-in by chromospheric emission. TheHα profiles of a few systems show a pure absorption line. The results are given in Table I.

Photometry of the contact binary system V471 Cas

UBV photoelectric observations of the W UMa-type binary V471 Cas were made from September to November 1984. Its colour indices were found to be(B-V)=0.m771±0.m02 and(U-B)=0.m196±0.m02. TheU, B, andV light curves of V471 Cas show some photometric fluctuations. We found that its orbital period is not 0.335998 days which was given by GCVS (1986), but 0.405356 days.Photometric orbital elements of V471 Cas were found using the Wilson-Devinney method. V471 Cas is a contact system, in which the overcontact factor is 0.19, its mass ratio of two components is 0.5947, and orbital minclination is in 83.29 degrees.

A new investigation of the peculiar binary star Epsilon Aurigae

Abstract We give results of photoelectric photometry and spectral observations of ϵ Aur during its 1982–1984 ingress and total eclipse. Narrow-band light curves and variations in radial velocity within a night resulting from autoregression analysis all indicate short time scale variations in the F supergiant primary on the order of hours or fractions thereof. Fluctuations with an amplitude of ±25 Km/s and a period of 400 d appear to be present in the measured radial velocity of the primary during ingress and totality. Obvious changes in the Hα profile were also observed: around the second contact of the total eclipse, there was emission in the blue wing; while around the third contact of the atmosphere eclipse, there was emission in the red wing.

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.

THE FUNDAMENTAL PARAMETERS, CHROMOSPHERIC ACTIVITY AND MAGNETIC FIELD MEASUREMENTS OF HR 5553

The CCD echelle spectra of the chromospherically active binary HR 5553 are obtained using the 2.16 m telescope with Coudé echelle spectrograph of Beijing Observatory in April 1996. The features of Ca II H & K, Hα, He I D3 and Ca II IRT2 (λ 8542 AA) & IRT3 (λ 8662 AA) are presented. The absolute fluxes of these lines which provide the useful information to study the chromospheric activity of HR 5553 are given. The fundamental parameters of the cool dwarf component of HR 5553 are determined using the analysis of the observed spectra with a resolution of R ≃ 60000 and signal-to-noise ratio S/N = 100 ∼ 300. A detailed spectroscopic analysis has yielded the following fundamental parameters: Effective temperature: Teff = 4881 K Surface gravity: log(g) = 3.65 Logarithmic iron abundance: [Fe/H] = –0.30 as well as that of other 12 metal elements (relative to the Sun) are listed in the Table II and Table III. Microturbulence: ζ = 1.20 km s-1. Magnetic field measurements of the cool dwarf component of HR 5553 have been made using the Stenflo-Lindegren statistical analysis and the profile-addition technique. The magnetic field strength and filling factor are obtained.

Photometric solutions and analysis of the Algol-type binary CI Aurigae

Abstract CI Aur is a short-period Algol-type eclipsing binary with a period of 1.870052 days. Photometric observations in UBV bands were made at McDonald Observatory between 1984 November and 1985 January. The light curves show random flickering and short-time variations. Photometric solutions were obtained using the Wilson-Devinney method. CI Aur is found to be a semi-detached system, with the less massive secondary component filling its Roche lobe. The mass ratio is 0.687 and the orbital inclination is 74° 42. Autoregressive power spectral analysis and harmonic analysis of the light curves were made. The results show that the oscillations are multiply quasi-periodic and have low amplitudes. Gas stream from the secondary strikes the trailing hemisphere of the primary. The disk produced by the star-stream interaction, is unstable. Two models of the star are discussed.