1-2.4 μm Near-IR Spectrum of the Giant Planet β Pictoris b Obtained with the Gemini Planet Imager

Abstract

Using the Gemini Planet Imager located at Gemini South, we measured the near-infrared(1.0–2.4μm)spectrum of the planetary companion to the nearby, young star β Pictoris. We compare the spectrum obtained with currently published model grids and with known substellar objects and present the best matching models as well as the best matching observed objects. Comparing the empirical measurement of the bolometric luminosity to evolutionary models, wefind a mass of 12.9±0.2Jup, an effective temperature of 1724±15 K, a radius of1.46±0.01 Jup, and a surface gravity of=glog4.18 0.01[dex](cgs). The stated uncertainties are statistical errors only, and do not incorporate any uncertainty on the evolutionary models. Using atmospheric models, we find an effective temperature of 1700–1800 K and a surface gravity o f=glog3.5–4.0[dex] depending upon the model. These values agree well with other publications and with“hot-start”predictions from planetary evolution models. Further, wefind that the spectrum ofβPicb best matches a low surface gravity L2±1 browndwarf. Finally, comparing the spectrum tofield brown dwarfs, wefind the the spectrum best matches 2MASSJ04062677–381210 and 2MASS J03552337+1133437.