Long-wavelength excesses in two highly obscured high-mass x-ray binaries: IGR J16318-4848 and GX 301-2

We present evidence for excess long-wavelength emission from two high-mass X-ray binaries, IGR J16318 - 4848 and GX 301 - 2, that show enormous obscuration (N-H similar or equal to 10(23) - 10(24) cm(-2)) in their X-ray spectra. Using archival near- and mid-infrared data, we show that the spectral energy distributions of IGR J16318 - 4848 and GX 301 - 2 are substantially higher in the mid- infrared than their expected stellar emission. We successfully fit the excesses with similar to 1000 K blackbodies, which suggests that they are due to warm circumstellar dust that also gives rise to the X- ray absorption. However, we need further observations to constrain the detailed properties of the excesses. This discovery highlights the importance of mid- infrared observations for understanding highly obscured X-ray binaries.