Eclipsing binaries observed with the WIRE satellite

I. Discovery and photometric analysis of the new bright A0 IV eclipsing binary ψ Centauri

¹ Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark e-mail: jvc@astro.ku.dk
² School of Physics A28, University of Sydney, 2006 NSW, Australia e-mail: bruntt@physics.usyd.edu.au
³ Department of Physics, University of Warwick, Coventry CV4 7AL, UK e-mail: jkt@astro.keele.ac.uk
⁴ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA e-mail: [gtorres;apenny]@cfa.harvard.edu
⁵ US Air Force Academy, Department of Physics, CO, USA e-mail: Derek.Buzasi@usafa.af.mil

Received: 18 May 2006
Accepted: 7 June 2006

Abstract

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 wire 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 wire 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 with an orbital period of 38.8 days from combining the wire light curve with data taken over two years from the Solar Mass Ejection Imager camera.

Results.We have fitted the light curve with ebop 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 and  K indicating masses of about 3.1 and 2.0. There is evidence in the wire light curve for g-mode pulsations in the primary star.