Discovery of a Hypervelocity L Subdwarf at the Star/Brown Dwarf Mass Limit
Abstract We report the discovery of a high-velocity, very low-mass star or brown dwarf whose kinematics suggest it is unbound to the Milky Way. CWISE J124909.08+362116.0 was identified by citizen scientists in the Backyard Worlds: Planet 9 program as a high-proper-motion ( μ = 0.″9 yr −1 ) faint red source. Moderate-resolution spectroscopy with Keck/NIRES reveals it to be a metal-poor early L subdwarf with a large radial velocity (−103 ± 10 km s −1 ), and its estimated distance of 125 ± 8 pc yields a speed of 456 ± 27 km s −1 in the Galactic rest frame, near the local escape velocity for the Milky Way. We explore several potential scenarios for the origin of this source, including ejection from the Galactic center ≳3 Gyr in the past, survival as the mass donor companion to an exploded white dwarf, acceleration through a three-body interaction with a black hole binary in a globular cluster, and accretion from a Milky Way satellite system. CWISE J1249+3621 is the first hypervelocity very low-mass star or brown dwarf to be found and the nearest of all such systems. It may represent a broader population of very high-velocity, low-mass objects that have undergone extreme accelerations.
Authors
- Adam C. Schneider (ORCID: https://orcid.org/0000-0002-6294-5937)
- Jacqueline K. Faherty (ORCID: https://orcid.org/0000-0001-6251-0573)
- Martin Kabatnik (ORCID: https://orcid.org/0000-0003-4905-1370)
- Dan Caselden (ORCID: https://orcid.org/0000-0001-7896-5791)
- Adam J. Burgasser (ORCID: https://orcid.org/0000-0002-6523-9536)
- S. L. Casewell (ORCID: https://orcid.org/0000-0003-2478-0120)
- J. Davy Kirkpatrick (ORCID: https://orcid.org/0000-0003-4269-260X)
- Thomas P. Bickle (ORCID: https://orcid.org/0000-0003-2235-761X)
- Kyle Kremer (ORCID: https://orcid.org/0000-0002-4086-3180)
- Christopher A. Theissen (ORCID: https://orcid.org/0000-0002-9807-5435)
- Hunter Brooks (ORCID: https://orcid.org/0000-0002-5253-0383)
- Austin Rothermich (ORCID: https://orcid.org/0000-0003-4083-9962)
- Aaron Meisner (ORCID: https://orcid.org/0000-0002-1125-7384)
- Emma Softich (ORCID: https://orcid.org/0000-0002-1420-1837)
- Marc J. Kuchner (ORCID: https://orcid.org/0000-0002-2387-5489)
- Preethi R. Karpoor (ORCID: https://orcid.org/0000-0002-1480-9041)
- Efrain Alvarado (ORCID: https://orcid.org/0009-0005-8159-8490)
- Roman Gerasimov (ORCID: https://orcid.org/0000-0003-0398-639X)
Institutions
- University of Notre Dame (US)
- The Graduate Center, CUNY (US)
- California Institute of Technology (US)
- Goddard Space Flight Center (US)
- American Museum of Natural History (US)
- University of Leicester (GB)
- City University of New York (US)
- Northern Arizona University (US)
- The Open University (GB)
- University of California San Diego (US)
- Hunter College (US)
- NSF NOIRLab (US)
- United States Naval Observatory (US)
- Infrared Processing and Analysis Center (US)
- University of California, Berkeley (US)
Publication Details
- Journal
- The Astrophysical Journal Letters
- Published
- 2024-08-01
- DOI
- https://doi.org/10.3847/2041-8213/ad6607
- Citations
- 5
- Primary Topic
- Stellar, planetary, and galactic studies
- Type
- article
- Field-Weighted Citation Impact
- 1.66
Funders
- National Science Foundation
- National Aeronautics and Space Administration
- W. M. Keck Foundation
- California Institute of Technology
- Space Telescope Science Institute
- Jet Propulsion Laboratory
- University of California, Los Angeles
- University of California, San Diego