Magellan Adaptive Optics first-light observations of the exoplanet beta Pic b. II. 3-5 micron direct imaging with MagAO+Clio, and the empirical bolometric luminosity of a self-luminous giant planet

Katie M. Morzinski; Jared R. Males; Andy J. Skemer; Laird M. Close; Phil M. Hinz; T. J. Rodigas; Alfio Puglisi; Simone Esposito; Armando Riccardi; Enrico Pinna; Marco Xompero; Runa Briguglio; Vanessa P. Bailey; Katherine B. Follette; Derek Kopon; Alycia J. Weinberger; Ya-Lin Wu

doi:10.1088/0004-637X/815/2/108

paper

Magellan Adaptive Optics first-light observations of the exoplanet beta Pic b. II. 3-5 micron direct imaging with MagAO+Clio, and the empirical bolometric luminosity of a self-luminous giant planet

arXiv:1511.02894 · doi:10.1088/0004-637X/815/2/108

Abstract

Young giant exoplanets are a unique laboratory for understanding cool, low-gravity atmospheres. A quintessential example is the massive extrasolar planet $β$ Pic b, which is 9 AU from and embedded in the debris disk of the young nearby A6V star $β$ Pictoris. We observed the system with first light of the Magellan Adaptive Optics (MagAO) system. In Paper I we presented the first CCD detection of this planet with MagAO+VisAO. Here we present four MagAO+Clio images of $β$ Pic b at 3.1 $μ$ m, 3.3 $μ$ m, $L^{'}$ , and $M^{'}$ , including the first observation in the fundamental CH $_{4}$ band. To remove systematic errors from the spectral energy distribution (SED), we re-calibrate the literature photometry and combine it with our own data, for a total of 22 independent measurements at 16 passbands from 0.99--4.8 $μ$ m. Atmosphere models demonstrate the planet is cloudy but are degenerate in effective temperature and radius. The measured SED now covers $>$ 80\% of the planet's energy, so we approach the bolometric luminosity empirically. We calculate the luminosity by extending the measured SED with a blackbody and integrating to find log( $L_{b o l}$ / $L_{S u n}$ ) $= - 3.78 \pm 0.03$ . From our bolometric luminosity and an age of 23 $\pm$ 3 Myr, hot-start evolutionary tracks give a mass of 12.7 $\pm$ 0.3 $M_{J u p}$ , radius of 1.45 $\pm$ 0.02 $R_{J u p}$ , and $T_{e f f}$ of 1708 $\pm$ 23 K (model-dependent errors not included). Our empirically-determined luminosity is in agreement with values from atmospheric models (typically $- 3.8$ dex), but brighter than values from the field-dwarf bolometric correction (typically $- 3.9$ dex), illustrating the limitations in comparing young exoplanets to old brown dwarfs.

Accepted to ApJ. 27 pages, 22 figures, 19 tables

Magellan Adaptive Optics first-light observations of the exoplanet beta Pic b. II. 3-5 micron direct imaging with MagAO+Clio, and the empirical bolometric luminosity of a self-luminous giant planet

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