Eclipsing binaries observed with the satellite

Context. Determinations of stellar mass and radius with realistic uncertainties at the level of 1% provide important constraints on models of stellar structure and evolution. Aims. We present a high-precision light curve of the A0 IV star ψ Centauri, from the star tracker on board the  satellite and the Solar Mass Ejection Imager camera on the Coriolis spacecraft. The data show that ψ Cen is an eccentric eclipsing binary system with a relatively long orbital period. Methods. The  light curve extends over 28.7 nights and contains 41 334 observations with 2 mmag point-to-point scatter. The eclipse depths are 0.28 and 0.16 mag, and show that the two eclipsing components of ψ Cen have very different radii. As a consequence, the secondary eclipse is total. We find the eccentricity to be e = 0.55 with an orbital period of 38.8 days from combining the  light curve with data taken over two years from the Solar Mass Ejection Imager camera. Results. We have fitted the light curve with  and have assessed the uncertainties of the resulting parameters using Monte Carlo simulations. The fractional radii of the stars and the inclination of the orbit have random errors of only 0.1% and 0.01 • , respectively, but the systematic uncertainty in these quantities may be somewhat larger. We have used photometric calibrations to estimate the effective temperatures of the components of ψ Cen to be 10 450 ± 300 and 8 800 ± 300 K indicating masses of about 3.1 and 2.0 M ⊙. There is evidence in the  light curve for g-mode pulsations in the primary star.