Discovery of the Exceptionally Short Period Ultracool Dwarf Binary LP 413-53AB

Abstract

We report the detection of large-amplitude, rapid radial velocity (RV) variations and line-splitting in high-resolution Keck/NIRSPEC spectra of the M9 dwarf LP 413-53. We attribute these features to binary motion. Analyzing data spanning 15 years, we infer a preliminary orbital period of 0.7106156$\pm$0.0000002 day, an eccentricity of 0.0088$\pm$0.0017, a primary RV semi-amplitude of 23.70$\pm$0.05 km s${}^{-1}$, and a secondary RV semi-amplitude of 28.41$\pm$0.06 km s${}^{-1}$, implying a system mass ratio $M_{\mathrm{secondary}}$/$M_{\mathrm{primary}}$ = 0.8340$\pm$0.0017. These measurements identify LP 413-53 as the shortest-period ultracool binary discovered to date, and one of the smallest separation main sequence binaries known. The position and velocity of the system rule out previously reported membership in the Hyades Moving Group, and indicate that this is likely a pair of evolved (age $\gtrsim$ 1 Gyr), very-low-mass stars. Assuming masses consistent with evolved late-M and L dwarfs, we estimate an orbital separation of 0.0081$-$0.0084 au or 17$-$19 stellar radii, and an orbital inclination angle of 24${}^{\circ }$, making it unlikely that this system exhibits eclipse events. The larger radii of these stars at young ages would have put them near contact at the system's current separation, and we speculate that this system has undergone dynamical evolution, either through orbital angular momentum loss or ejection of a third component followed by tidal circularization. While further observations are needed to fully constrain the orbital and physical parameters of LP 413-53, this ultra-short-period UCD binary system serves as a new testbed for formation and dynamical evolution models of very-low-mass multiples.

Accepted to ApJ Letters; 15 pages, 3 figures

References in corpus (14)

• Achieving better than 1 minute accuracy in the Heliocentric and Barycentric Julian Dates
• Constraining the Age-Activity Relation for Cool Stars: The SDSS DR5 Low-Mass Star Spectroscopic Sample
• The 0.8-14.5 micron Spectra of Mid-L to Mid-T Dwarfs: Diagnostics of Effective Temperature, Grain Sedimentation, Gas Transport, and Surface Gravity
• The H$\alpha$ emission of nearby M dwarfs and its relation to stellar rotation
• The NASA-UC-UH Eta-Earth Program: IV. A Low-mass Planet Orbiting an M Dwarf 3.6 PC from Earth
• SpeX Spectroscopy of Unresolved Very Low Mass Binaries. II. Identification of Fourteen Candidate Binaries with Late-M/Early-L and T Dwarf Components
• Python Leap Second Management and Implementation of Precise Barycentric Correction (barycorrpy)
• Flux calibration of medium-resolution spectra from 300 nm to 2500 nm: Model reference spectra and telluric correction
• Exploring the age dependent properties of M and L dwarfs using Gaia and SDSS
• The Gaia Ultra-Cool Dwarf Sample -- II: Structure at the end of the main sequence
• TOI-811b and TOI-852b: New transiting brown dwarfs with similar masses and very different radii and ages from the TESS mission
• The 3-D Kinematics of the Orion Nebula Cluster: NIRSPEC-AO Radial Velocities of the Core Population
• Astrometric orbits of spectral binary brown dwarfs I: Massive T dwarf companions to 2M1059$-$21 and 2M0805$+$48
• Metadata and Data Management for the Keck Observatory Archive

Cited by in corpus (7)

• The cool brown dwarf Gliese 229 B is a close binary
• A transiting brown dwarf in a 2 hour orbit
• Rotation and Abundances of the Benchmark Brown Dwarf HD 33632 Ab from Keck/KPIC High-resolution Spectroscopy
• PDS 70b Shows Stellar-like Carbon-to-oxygen Ratio
• Two warm Earth-sized exoplanets and an Earth-sized candidate in the M5V-M6V binary system TOI-2267
• Distinct Rotational Evolution of Giant Planets and Brown Dwarf Companions
• A Mass Transferring Brown Dwarf Binary on a 57 Minute Orbit