Near-Infrared SOAR Photometric Observations of Post Common Envelope Binaries

Abstract

{From a number of today known Post Common Envelopes Binaries (PCEB) only a handful has yet been observed at near-infrared (NIR) wavelengths and an even smaller number has modeled NIR light curves. At shorter wavelengths one has access to the cooler and larger components of these systems and has the chance to detect emission from its faint and heavily irradiated atmospheres. } {By modeling NIR light curves of PCEBs we intent to constrain their system parameters and study the properties of the system components.} {Here we present simultaneous NIR $JHK_s$ light curves of two PCEBs obtained with the $4m$ SOAR telescope.} {%For this work we have selected 3 systems from a previously selected sample of 8 PCEBs. KV Vel and TW Crv are long period (P$_{\rm orb} =$ 8.6h and 7.9h, respectively) PCEBs with large irradiation effects. The results of light curve fitting provided solutions with inclination $i = (47\pm5)^\circ$, mass ratio $q = 0.3\pm0.1$ and radius of the secondary $R_2/a = 0.24^{+0.05}_{-0.03}$ (where $a$ is the orbital separation) for KV Vel, and $i = (42\pm9)\degr$, $q = 0.28\pm0.04$ and $R_2/a = 0.22\pm0.01$ for TW Crv, respectively. For KV Vel, we obtain an average value for the albedo of the secondary star of $\alpha = 0.43$, consistent in the $J$, $H$ and $K_s$-bands. For TW Crv, on the other hand, we obtain values of $\alpha_{J} = (0.4\pm0.1)$ and $\alpha_{H} = (0.3\pm0.1)$ for the $J$- and $H$-bands, respectively.