HD 106906 b: A planetary-mass companion outside a massive debris disk


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We report the discovery of a planetary-mass companion, HD 106906 b, with the new Magellan Adaptive Optics (MagAO) + Clio2 system. The companion is detected with Clio2 in three bands: J , K S , and L  , and lies at a projected separation of 7.1'' (650 AU). It is confirmed to be comoving with its 13+/-2 Myr-old F5 host using Hubble Space Telescope/Advanced Camera for Surveys astrometry over a time baseline of 8.3 yr. DUSTY and COND evolutionary models predict the companion's luminosity corresponds to a mass of 11+/-2 M Jup , making it one of the most widely separated planetary-mass companions known. 

We classify its Magellan/Folded-Port InfraRed Echellette J/H/K spectrum as L 2.5+/-1 ; the triangular H -band morphology suggests an intermediate surface gravity. HD 106906 A, a pre-main-sequence Lower Centaurus Crux member, was initially targeted because it hosts a massive debris disk detected via infrared excess emission in unresolved Spitzer imaging and spectroscopy. 

The disk emission is best fit by a single component at 95 K, corresponding to an inner edge of 15-20 AU and an outer edge of up to 120 AU. If the companion is on an eccentric ( e>0.65 ) orbit, it could be interacting with the outer edge of the disk. Close-in, planet-like formation followed by scattering to the current location would likely disrupt the disk and is disfavored. Furthermore, we find no additional companions, though we could detect similar-mass objects at projected separations >35 AU. In situ formation in a binary-star-like process is more probable, although the companion-to-primary mass ratio, at <1% , is unusually small.

Vanessa Bailey, Tiffany Meshkat, Megan Reiter, Katie Morzinski, Jared Males, Kate Y. L. Su, Philip M. Hinz, Matthew Kenworthy, Daniel Stark, Eric Mamajek, Runa Briguglio, Laird M. Close, Katherine B. Follette, Alfio Puglisi, Timothy Rodigas, Alycia J. Weinberger, Marco Xompero (Submitted on 4 Dec 2013)

Comments: 7 pages, 3 figures, accepted to ApJL

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Cite as: arXiv:1312.1265 [astro-ph.EP] (or arXiv:1312.1265v1 [astro-ph.EP] for this version)

Submission history From: Vanessa Bailey [ [v1] Wed, 4 Dec 2013 18:11:41 GMT (350kb,D) 

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