Context : Directly imaged planets are ideal candidates for spectroscopic characterization of their atmospheres .
The angular separations that are typically close to their host stars , however , reduce the achievable contrast and thus signal-to-noise ratios ( S/N ) .

Aims : We spectroscopically characterize the atmosphere of HD 106906 b , which is a young low-mass companion near the deuterium burning limit .
The wide separation from its host star of 7.1″ makes it an ideal candidate for high S/N and high-resolution spectroscopy .
We aim to derive new constraints on the spectral type , effective temperature , and luminosity of HD 106906 b and also to provide a high S/N template spectrum for future characterization of extrasolar planets .

Methods : We obtained 1.1–2.5 \muup m integral field spectroscopy with the VLT/SINFONI instrument with a spectral resolution of R \approx 2000–4000 .
New estimates of the parameters of HD 106906 b are derived by analyzing spectral features , comparing the extracted spectra to spectral catalogs of other low-mass objects , and fitting with theoretical isochrones .

Results : We identify several spectral absorption lines that are consistent with a low mass for HD 106906 b .
We derive a new spectral type of L1.5 \pm 1.0 , which is one subclass earlier than previous estimates .
Through comparison with other young low-mass objects , this translates to a luminosity of log ( L / L _ { \odot } ) = -3.65 \pm 0.08 and an effective temperature of T _ { eff } = 1820 \pm 240 K. Our new mass estimates range between M = 11.9 ^ { +1.7 } _ { -0.8 } M _ { Jup } ( hot start ) and M = 14.0 ^ { +0.2 } _ { -0.5 } M _ { Jup } ( cold start ) .
These limits take into account a possibly finite formation time , i.e. , HD 106906 b is allowed to be 0–3 Myr younger than its host star .
We exclude accretion onto HD 106906 b at rates \dot { M } > 4.8 \times 10 ^ { -10 } M _ { Jup } yr ^ { -1 } based on the fact that we observe no hydrogen ( Paschen- \beta , Brackett- \gamma ) emission .
This is indicative of little or no circumplanetary gas .
With our new observations , HD 106906 b is the planetary-mass object with one of the highest S/N spectra yet .
We make the spectrum available for future comparison with data from existing and next-generation ( e.g. , ELT and JWST ) spectrographs .

Conclusions :