CCD photometry of variable stars in the Magellanic Clouds - V. The eclipsing binaries HV1620 and HV2241

Abstract

Using improved techniques, high-quality CCD uvbyVI_C photometry has been obtained for the 14th magnitude eclipsing binaries HV1620 in the Small Magellanic Cloud (SMC) and HV2241 in the Large Magellanic Cloud (LMC). IUE ultraviolet spectrophotometry was also obtained. These data have been analysed using the Wilson & Devinney synthetic light-curve code and Kurucz model atmospheres. Both systems are semi-detached and appear to have undergone mass exchange. In HV1620 the mass ratio and the effective temperatures of the primary and secondary are q=M_2/M_1=0.68+/-0.03, T_eff,1=33000+/-4500K and T_eff,2=24000+/-3500K. The corresponding values for HV2241 are 0.53+/-0.01, 27000+/-3000K and 20200+/-1500K. Using the radial-velocity curves obtained by Niemela & Bassino with a 1-m telescope, we find that both systems are massive, as expected. Reddening considerations suggest both systems may lie towards the rear of their respective Clouds.