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G. Torres, J. Mader (CfA), L. A. Marschall (Gettysburg College), R. Neuhaeuser (MPE, Germany), A. S. Duffy (Gettysburg College)
BD+05\arcdeg706 is an example of a rare class of a dozen or so interacting binaries called ``cool Algols", in which both components of the system are late-type stars. By contrast, the ``classical Algols" are systems in which the star transfering mass is of late spectral type, but the mass gainer is much hotter. BD+05\arcdeg706 was shown previously to be eclipsing (Marschall, Torres & Neuhaeuser 1998, BAAS, 30, 835). In this paper we report our complete analysis of BVRI light curves for the system obtained at Gettysburg College Observatory, together with spectroscopy from the Harvard-Smithsonian Center for Astrophysics reported previously (Torres, Neuhaeuser & Wichmann 1998, AJ, 115, 2028), and X-ray observations obtained with the ROSAT satellite. Our light curve analysis indicates the presence of spots, most likely on the more massive, active component (primary), which change from season to season. Our results confirm the semi-detached nature of the system, and combined with the spectroscopy they have allowed us to obtain the most precise absolute masses and radii for any object of this class. Our X-ray light curve for BD+05\arcdeg706 shows the primary eclipse clearly, but no sign of a secondary eclipse, confirming that the primary is the active star. Strong X-ray flares are also visible.