BH Vir Research Articles

Starspot Activity on Short-period RS CVn Stars

We have yet to understand the magnetic activity cycles of cool close binary systems of sunlike stars. Mutual tidal interactions, as well as magnetic ones, may result from a regime of dynamo models not yet tested, because these have been developed for single stars. To arrive at the basic physics, though, requires that we first examine the phenomenology of magnetic activity for binary systems. In particular, we would like to discover if such activity has a clearly-defined cycle, such as the sun exibits.Among the proxy indicators of magnetic activity are the Ca II H and K lines. Strassmeier et al. (1988) used the strength of these lines as the primary criterion for the inclusion of systems in The Catalog of Chromospherically Binary Stars. Of the RS CVn stars in the catalog, 12 have orbital periods of one day or shorter; 9 are eclipsing systems. As part of a decade-long program, we have focussed our observations and models on eight of the short-period group (Hall, 1976): XY UMa, UV Psc, SV Cam, RT And, CG Cyg, ER Vul, BH Vir, and WY Cnc. These close systems are tidally-locked in synchronous rotation and tidally-distorted into Roche lobe configurations.

Long-term starspot activity of short-period RS Canum Venaticorum stars. IV - WY CANCRI

The photometric distortion waves in the short-period RS CVn system WY CnC are parametrized by a dark, circular spot model for the active regions on the primary star. From recent observations and archival sources, the changes in positions and areas of the active regions are inferred. For light curves with simultaneous visual and red or infrared data, the average temperatures of the spotted regions relative to the photosphere are evaluated. In 1989, it is found that T(spot) = 3970 + or - 300 K for a primary star temperature of 5520 K. Some indication is found of a nonuniform temperature distribution in longitude across the spotted area at this time. The active regions tend to occur at low latitudes, in contrast to the high latitudes previously found for SV Cam, RT And, and BH Vir. It is found again that the active regions fall into preferred longitudes near 90 and 270 deg. 27 refs.

The photometric behaviour of BH Vir

Visible light curves of the RS CVn short-period system BH Vir, collected over 26 years, have been analyzed.B-V colours indicate that the primary minimum is normally redder than one would expect, assuming the spectroscopic classification of the system components, while the secondary yielded bluer. A qualitative comparison of the different light curves, suggests that not only cool starspots are the reason of the observed variability.

Long-term starspot activity of short-period RS Canum Venaticorum stars. III - BH Virginis

The photometric distortion waves in the light curves of the short-period RS CVn system BH Vir by a dark, circular spot model for the active regions on the primary star is parameterized. Recent observations and archival sources are used to infer the positions and areas of the active regions. For light curves with simultaneous B and R or V and I data, the temperatures of the spotted regions relative to the photospheres can be evaluated. For BH Vir in 1986, T(spot) = 4900 + or - 500 K. The active regions tend to occur at high latitudes and at preferred longitudes near 90 and 270 deg. 32 refs.

Lightcurve analysis for the eclipsing binaries ST Car, RY Ind and BH Vir

Lightcurve analysis for the eclipsing binaries ST Car, RY Ind and BH Vir