CCD photometry of variable stars in the Magellanic Clouds -- VI. The eclipsing binary HV 982 in the Large Magellanic Cloud

Abstract

Using improved techniques, high‐quality CCD uvbyVI photometry has been obtained for the eclipsing binary HV 982 in the Large Magellanic Cloud (LMC). International Ultraviolet Explorer ultraviolet spectrophotometry was also obtained. These data have been analysed using the Wilson–Devinney synthetic light‐curve code and Kurucz low‐metallicity model atmospheres as well as the EBOP code. The system is detached and the orbit is eccentric. Apsidal motion is detected with apsidal period 205 ± 7 yr. The effective temperatures of the components are found via flux fitting to be Teff,1 = 28 000 ± 5000 K and Teff,2 = 27 200 ± 5000 K. The large errors result from uncertainties over the appropriate interstellar extinction correction. The system plausibly comprises two ∼ 8 M stars of radius 6–7 R separated by ∼ 30 R. For pedagogical and historical interest, the near simultaneity of the eclipse minima at different wavelengths is used to constrain the constancy of the speed of light with wavelength and the mass of the photon, yielding mγ < 10−41 kg. Because of the great distance to HV 982, this limit is some 102 times smaller than previously achieved with eclipse timings, but it is nevertheless 10 orders of magnitude less stringent than that which is provided by satellite measurements of planetary magnetic fields.

Eclipsing binaries in the Magellanic Clouds

“…CCD light curves obtained at Mt. John University Observatory, New Zealand by Pritchard et al (1998b) clearly confirm these characteristics. Furthermore, with new minima observations, apsidal motion with a period of about 200 yr could be detected, making HV 982 just the second MC eclipsing binary with measured orbital motion (the first known case is HV 2274, also in the LMC; Watson et al 1992;Ribas et al 2000).…”

“…Meanwhile, dedicated CCD light curve observations have been done for several LMC and SMC systems at Mt. John University Observatory, New Zealand (Pritchard et al 1998a(Pritchard et al , 1998b and references therein), and several thousands of new systems have been discovered from the EROS, MACHO, and OGLE microlensing projects (e.g. Grison et al 1995;Alcock et al 1997;Udalski et al 1998b).…”

“…Very recently, accurate distances and dimensions for two additional LMC systems, HV 982 (Pritchard et al 1998b;Fitzpatrick et al 2002) and EROS1044 , have become available. A comparison of the results for HV 2274, HV 982, and EROS1044, and a discussion of the derived distances to the optical center of the LMC is given by Ribas et al (2002).…”

Apsidal motion and absolute parameters for five LMC eccentric eclipsing binaries

“…It was discovered to be a variable star by Gaposhkin (1970), who published the first photographic light curve. Pritchard et al (1994Pritchard et al ( , 1998 in their photometric study derived high surface temperatures (∼28 000 K) and masses (∼8 M ) of components. They also derived the apsidal motion period U = 205 ± 7 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.…”