Eclipsing binaries in the Magellanic Clouds

Abstract

Abstract. We present new accurate CCD uvby light curves for the LMC eclipsing binaries HV 982 and HV 12578, and for the SMC systems HV 1433 and HV 11284 obtained at the Danish 1.5 m telescope at ESO, La Silla. The light curves were derived from DoPHOT photometry, and typical accuracies are between 0.007 and 0.012 mag per point. Standard uvby indices have also been established for each binary, primarily for determination of interstellar reddening and absorption. For HV 982 and HV 12578, accurate photometric elements have been established. Both systems consist of two detached components of comparable sizes in an eccentric orbit. Adopting the spectroscopic elements given by Fitzpatrick et al. (2002) for HV 982, we derive absolute dimensions of its components which agree well with their results. A distance modulus of V 0 − M V = 18.63±0.08 is obtained, corresponding to a distance of 53.2± 2.0 kpc, which is in formal agreement with (although slightly larger than) their determination. HV 1433 and HV 11284 both consist of two rather close, deformed and quite different stars. As the mass ratios between the components (and their rotation rates) are not known, definitive photometric elements can not yet be obtained, but we present a sample of possible photometric solutions. In a series of forthcoming papers we will combine our uvby observations with high-dispersion spectra from the UVES spectrograph on the ESO Very Large Telescope (VLT) and present absolute dimensions, chemical abundances and distances for selected LMC and SMC systems, including HV 12578 and refined results for HV 982.

The present-day chemical composition of the LMC

“…2) obtained by the 6 analyses given in Table 7 Hilker et al 1995;Larsen et al 2000). However, these photometric metallicities are absolute estimates measured relative to the Sun, and so may not be directly comparable to the results presented in Table 7.…”

Apsidal motion and absolute parameters for five LMC eccentric eclipsing binaries

“…Later, Clausen et al (2003) presented a new accurate CCD uvby light curve obtained at the Danish 1.54 m telescope at La Silla and derived the precise photometric elements with apsidal motion period U = 208 ± 15 years.…”

“…All CCD times of minimum light given in Pritchard et al (1998) and Clausen et al (2003) were incorporated into our analysis. Using Macho (Faccioli et al 2007) and Ogle (Graczyk et al 2011) photometry, we were able to derive additional times of minimum light.…”

Detached binaries in the Large Magellanic Cloud

“…So far, seven systems were used to get its distance. Out of them, only three, HV 2274 Udalski et al 1998a;Ribas et al 2000;Nelson et al 2000;Groenewegen & Salaris 2001;Fitzpatrick et al 2002), EROS 1044 and HV 982 Clausen et al 2003), are DEBs. Out of the remaining four, three, i.e.…”