摘要
用北京天文台兴隆60厘米镜于1977年取得此星960个黄光光电测光观测点,光变曲线呈大陵五型。1978年发表了Russell-Merrill测光解。1982年在美国用Wilson-Devinney程序算得10组测光解,解的残差对于质量比很不敏感。为了解决测光解的不定性,1985—86年用加拿大1.8米镜测得两子星视向速度曲线;得质量比为0.53±0.01。重新求测光解并结合分光解得F型主星和较冷伴星的质量各为1.43±0.05和0.76+0.02M_⊙。虽然是不接双星,但伴星只比其临界等位面稍小一点。这对双星像是不久前才由大陵五型半接双星演化而来的新阶段品种。
A yellow light curve of this short-period (P=0.d935298) binary based On 960 photoelectric observations using the 60-cm reflector at the Xinglong station of the Beijing Astronomical Observatory turned out to be of Algol type. In a first analysis a Russell-Merrill photometric solution and semidetached model were published, without abstract in English. 90 normal points were employed in computing 10 Wilson-Devinney light curve-synthesis solutions in 1982. Detached mode solutions were to be preferred over semidetached ones in having smaller residuals. However, in the 10 detached mode solutions the weighted (O-C) residuals only fluctuated between 0.010 and 0.013 as the mass ratio, M2/M1 (l=the hotter component), was allowed to vary in a wide range from 0.18 to 7.9.To resolve the indeterminacy of the photometric solutions Lu secured in 1985-86 radial velocity observations at the Dominion Astrophysical Observatory (DAO) using the 1.8 m telescope image tube spectrograph and a Reticon detector system. Fortunately the star was observed to be a two-spectra binary. Despite relatively large residuals in the spectroscopic orbits, we found good agreement between the independently determined systemic velocities, V01 and V02. A spectroscopic mass ratio of M2/M1 = 0.528± 0.013 and a spectral type of F7 for the hotter component-dominated blue-violet spectrum from DAO spectroscopy enabled yet another Wilson-Devinney photometric solution to be found on the Beijing Astronomical Observatory VAX 11/ 780 computer and is given in Table 2.The masses of the components are found to be 1.43 ± 0.05 M for the F star, and 0.76 ± 0.02 M for the cooler companion. These data, along with the derived radii and estimated radiative properties, are listed in Table 6 where we give also, at the bottom, a rough idea of the distance to CG Virginis. A simplistic comparison with de Jager et al. would indicate classifications of something like F6IV and K5V for the two stars.Although this binary is a detached system, with Ωinn/Ω2 =0.964 the less massive, cooler component just barely underfills its Roche lobe. And the system .shares a number of properties in common with Algol binaries . In line with C. de Loore it appears likely that CG Virginis might have evolved into the current detached phase from an Algol-like binary for a period not so long, thus retaining some of its former characteristics. To test the validity of this or other scenarios both theoretical and much-improved observational work, compared with which the present study is but a preliminary crude effort, are needed.
