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Published March 20, 2014 | Published + Submitted
Journal Article Open

Spectroscopic Confirmation of Young Planetary-Mass Companions on Wide Orbits

Abstract

We present moderate-resolution (R ~ 4000-5000) near-infrared integral field spectroscopy of the young (1-5 Myr) 6-14 M_(Jup) companions ROXs 42B b and FW Tau b obtained with Keck/OSIRIS and Gemini-North/NIFS. The spectrum of ROXs 42B b exhibits clear signs of low surface gravity common to young L dwarfs, confirming its extreme youth, cool temperature, and low mass. Overall, it closely resembles the free-floating 4-7 M_(Jup) L-type Taurus member 2MASS J04373705+2331080. The companion to FW Tau AB is more enigmatic. Our optical and near-infrared spectra show strong evidence of outflow activity and disk accretion in the form of line emission from [S II], [O I], Hα, Ca II, [Fe II], Paβ, and H2. The molecular hydrogen emission is spatially resolved as a single lobe that stretches ≈0.''1 (15 AU). Although the extended emission is not kinematically resolved in our data, its morphology resembles shock-excited H2 jets primarily seen in young Class 0 and Class I sources. The near-infrared continuum of FW Tau b is mostly flat and lacks the deep absorption features expected for a cool, late-type object. This may be a result of accretion-induced veiling, especially in light of its strong and sustained Hα emission (EW(Hα) ≳ 290 Å). Alternatively, FW Tau b may be a slightly warmer (M5-M8) accreting low-mass star or brown dwarf (0.03-0.15 M_☉) with an edge-on disk. Regardless, its young evolutionary stage is in stark contrast to its Class III host FW Tau AB, indicating a more rapid disk clearing timescale for the host binary system than for its wide companion. Finally, we present near-infrared spectra of the young (~2-10 Myr) low-mass (12-15 M_(Jup)) companions GSC 6214-210 B and SR 12 C and find they best resemble low-gravity M9.5 and M9 substellar templates.

Additional Information

© 2014 The American Astronomical Society. Received 2013 November 25; accepted 2014 January 28; published 2014 March 5. We are grateful to the referee for prompt and useful feedback, Bo Reipurth and Lynne Hillenbrand for helpful comments on the properties of FW Tau b, Katelyn Allers for the low-gravity spectral templates used in this work, and Kimberly Aller and Will Best for carrying out some of the IRTF observations. It is also a pleasure to thank Joel Aycock, Randy Campbell, Heather Hershley, Jim Lyke, Julie Rivera, Hien Tran, Cindy Wilburn and the entire Keck staff for their support with the observations. B.P.B. and M.C.L. have been supported by NASA grant NNX11AC31G and NSF grant AST09-09222. Some of this work is based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência, Tecnologia e Inovação (Brazil) and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina) We utilized data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. NASA's Astrophysics Data System Bibliographic Services together with the VizieR catalog access tool and SIMBAD database operated at CDS, Strasbourg, France, were invaluable resources for this work. Finally, mahalo nui loa to the kama'āina of Hawai'i for their support of Keck and the Mauna Kea observatories. We are grateful to conduct observations from this mountain. Facilities: Keck:II (OSIRIS, NIRC2) - KECK II Telescope, Keck:I (OSIRIS) - KECK I Telescope, Gemini:Gillett (NIFS) - Gillett Gemini North Telescope, IRTF (SpeX) - Infrared Telescope Facility, UH:2.2m (SNIFS) - University of Hawaii 2.2 meter Telescope

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Published - 0004-637X_784_1_65.pdf

Submitted - 1401.7668v1.pdf

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August 20, 2023
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