The direct detection of the irradiated brown dwarf in the white dwarf - brown dwarf binary SDSS J141126.20+200911.1

TL;DR

This study presents the first direct detection of the dark side of an irradiated brown dwarf in a white dwarf binary, revealing unexpected temperature characteristics likely caused by UV irradiation effects.

Contribution

It provides the first direct near-IR detection of the dark side of an irradiated brown dwarf in a white dwarf binary and discusses UV irradiation effects on observed temperatures.

Findings

Detection of the brown dwarf's dark side in the H band.

Inconsistent temperature estimates suggest UV irradiation causes artificial brightening.

Irradiation effects may be characteristic of similar binary systems.

Abstract

We have observed the eclipsing, post-common envelope white dwarf-brown dwarf binary, SDSS141126.20+200911.1, in the near-IR with the HAWK-I imager, and present here the first direct detection of the dark side of an irradiated brown dwarf in the $H$ band, and a tentative detection in the $K_s$ band. Our analysis of the lightcurves and indicates that the brown dwarf is likely to have an effective temperature of 1300 K, which is not consistent with the effective temperature of 800 K suggested by its mass and radius. As the brown dwarf is already absorbing almost all the white dwarf emission in the $K_s$ band we suggest that this inconsistency may be due to the UV-irradiation from the white dwarf inducing an artificial brightening in the $K_s$ band, similar to that seen for the similar system WD0137-349B, suggesting this brightening may be characteristic of these UV-irradiated binaries.