Eclipsing binaries in the Magellanic Clouds. uvby CCD light curves and photometric analyses for HV982 (LMC), HV12578 (LMC), HV1433 (SMC), and HV11284 (SMC)

摘要

We present new accurate CCD uvby light curves for the LMC eclipsing binariesHV982 and HV12578, and for the SMC systems HV1433 and HV11284 obtained at theDanish 1.5m telescope at ESO, La Silla. The light curves were derived fromDoPHOT photometry, and typical accuracies are between 0.007 and 0.012 mag perpoint. Standard uvby indices have also been established for each binary,primarily for determination of interstellar reddening and absorption. For HV982and HV12578, accurate photometric elements have been established. Both systemsconsist of two detached components of comparable sizes in an eccentric orbit.Adopting the spectroscopic elements given by Fitzpatrick et al. 2002 for HV982,we derive absolute dimensions of its components which agree well with theirresults. A distance modulus of V_0-M_V = 18.63 +/- 0.08 is obtained,corresponding to a distance of 52.6 +/- 2.0 kpc, which is in formal agreementwith (although slightly larger than) their determination. HV1433 and HV11284both consist of two rather close, deformed and quite different stars. As themass ratios between the components (and their rotation rates) are not known,definitive photometric elements can not yet be obtained, but we present asample of possible photometric solutions. In a series of forthcoming papers wewill combine our uvby observations with high-dispersion spectra from the UVESspectrograph on the ESO Very Large Telescope (VLT) and present absolutedimensions, chemical abundances and distances for selected LMC and SMC systems,including HV12578 and refined results for HV982.