An Alma Disk Mass for the Candidate Protoplanetary Companion to FW Tau

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Kraus, Adam L.
Andrews, Sean M.
Bowler, Brendan P.
Herczeg, Gregory
Ireland, Michael J.
Liu, Michael C.
Metchev, Stanimir
Cruz, Kelle L.

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We present ALMA observations of the FW Tau system, a close binary pair of M5 stars with a wide-orbit (300 AU projected separation) substellar companion. The companion is extremely faint and red in the optical and near-infrared, but boasts a weak far-infrared excess and optical/near-infrared emission lines indicative of a primordial accretion disk of gas and dust. The component-resolved 1.3mm continuum emission is found to be associated only with the companion, with a flux (1.78 +/- 0.03 mJy) that indicates a dust mass of 1-2M(circle plus). While this mass reservoir is insufficient to form a giant planet, it is more than sufficient to produce an analog of the Kepler-42 exoplanetary system or the Galilean satellites. The mass and geometry of the disk-bearing FW Tau companion remains unclear. Near-infrared spectroscopy shows deep water bands that indicate a spectral type later than M5, but substantial veiling prevents a more accurate determination of the effective temperature (and hence mass). Both a disk-bearing "planetary-mass" companion seen in direct light or a brown dwarf tertiary viewed in light scattered by an edge-on disk or envelope remain possibilities.



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Kraus, Adam L., Sean M. Andrews, Brendan P. Bowler, Gregory Herczeg, Michael J. Ireland, Michael C. Liu, Stanimir Metchev, and Kelle L. Cruz. "An ALMA Disk Mass for the Candidate Protoplanetary Companion to FW Tau." The Astrophysical Journal Letters, Vol. 798, No. 1 (Jan., 2015): L23.