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Published October 1, 2015 | Published + Submitted
Journal Article Open

Near-Infrared Spectroscopy of 2M0441+2301 AabBab: A Quadruple System Spanning the Stellar to Planetary Mass Regimes


We present Keck/NIRC2 and OSIRIS near-infrared imaging and spectroscopy of 2M0441+2301 AabBab, a young (1–3 Myr) hierarchical quadruple system comprising a low-mass star, two brown dwarfs, and a planetary-mass companion in Taurus. All four components show spectroscopic signs of low surface gravity, and both 2M0441+2301 Aa and Ab possess Paβ emission indicating they each harbor accretion subdisks. Astrometry spanning 2008–2014 reveals orbital motion in both the Aab (0."23 separation) and Bab (0."095 separation) pairs, although the implied orbital periods of >300 years mean dynamical masses will not be possible in the near future. The faintest component (2M0441+2301 Bb) has an angular H-band shape, strong molecular absorption (VO, CO, H_2O, and FeH), and shallow alkali lines, confirming its young age, late spectral type (L1 ± 1), and low temperature (≈1800 K). With individual masses of 200_(-50)^(+100) M_(Jup), 35 ± 5 M_(Jup), 19 ± 3 M_(Jup), and 9.8 ± 1.8 M_(Jup), 2M0441+2301 AabBab is the lowest-mass quadruple system known. Its hierarchical orbital architecture and mass ratios imply that it formed from the collapse and fragmentation of a molecular cloud core, demonstrating that planetary-mass companions can originate from a stellar-like pathway analogous to higher-mass quadruple star systems as first speculated by Todorov et al. More generally, cloud fragmentation may be an important formation pathway for the massive exoplanets that are now regularly being imaged on wide orbits.

Additional Information

© 2015. The American Astronomical Society. Received 2015 August 14; accepted 2015 September 4; published 2015 September 28. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. We thank K. Deck for helpful suggestions for improving this article, M. Brown for contributing telescope time for our NIRC2 observations, and the entire Keck Observatory staff for their exceptional support. 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. NASAʼs 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. This research has benefitted from the SpeX Prism Spectral Libraries, maintained by Adam Burgasser at http://pono.ucsd. edu/-adam/browndwarfs/spexprism. 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 (NIRC2), Keck:I (OSIRIS).

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Published - Bowler_2015pL30.pdf

Submitted - 1509.01658v2.pdf


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