Near-infrared SOAR photometric observations of post common envelope binaries^⋆

Departamento de FísicaUniversidade Federal de Santa Catarina, Campus Trindade, 88040-900 Florianópolis, SC, Brazil
e-mail: tiago@astro.ufsc.br

Received: 8 September 2010
Accepted: 19 November 2010

Abstract

Context. From a number of known post common envelopes binaries (PCEB) only a handful have yet been observed at near-infrared (NIR) wavelengths, and even fewer have modeled NIR light curves. At shorter wavelengths one has access to the cooler and larger components of these systems and has a chance to detect emission from its faint and heavily irradiated atmospheres.

Aims. By modeling NIR light curves of PCEBs, we intend to constrain their system parameters and study the properties of the system components.

Methods. Here we present simultaneous NIR JHK_s light curves of two PCEBs obtained with the 4 m SOAR telescope.

Results.KV Vel and TW Crv are long-period (P_orb = 8.6 h and 7.9 h, respectively) PCEBs with strong irradiation effects. The results of light-curve fitting provided solutions with inclination i = (47 ± 5)°, mass ratio q = 0.3 ± 0.1, and radius of the secondary ${\mathit{R}}_{\mathrm{2}}\mathit{/}\mathit{a}\mathrm{=}\mathrm{0.2}{\mathrm{4}}_{-0.03}^{\mathrm{+}\mathrm{0.05}}$ (where a is the orbital separation) for KV Vel, and i = (42 ± 9)°, q = 0.28 ± 0.04, and R₂/a = 0.22 ± 0.01 for TW Crv, respectively. For KV Vel, we obtain an average value for the albedo of the secondary star of α = 0.43, consistent in the J, H and K_s band. For TW Crv, on the other hand, we obtain values of α_J = (0.4 ± 0.1) for the J and α_H = (0.3 ± 0.1) for H-band.