Discovery of a Binary Brown Dwarf at 2 Parsecs from the Sun
This paper reports the identification and characterization of a binary brown dwarf system, WISE J104915.57-531906.1, located at a distance of 2 parsecs from the Sun, making it the third closest stellar system known after Alpha Centauri and Barnard's Star. The identification was a result of a comprehensive search using multi-epoch astrometric data from the Wide-field Infrared Survey Explorer (WISE) and corroborative data from several other astronomical surveys, including the Digitized Sky Survey, the Two Micron All-Sky Survey (2MASS), and the Deep Near-Infrared Survey of the Southern Sky (DENIS).
The newly discovered system, hereafter referred to as WISE 1049−5319, exhibits significant proper motion, estimated at µαcosδ = −2.759 ± 0.006 arcsec/yr and µδ = +0.354 ± 0.006 arcsec/yr. Spectroscopic observations performed using the Gemini Multi-Object Spectrograph (GMOS) at the Gemini South telescope identified the primary component of the binary system as an L8±1 spectral type brown dwarf. The paper posits that the secondary component likely resides near the L/T spectral transition, considering the brightness difference of Δi = 0.45 mag relative to the primary.
The single-band parallax of 0.496±0.037 arcsec was derived from the combined astrometric data, yielding a precise distance measurement of 2.0±0.15 parsecs. The proximity of this system presents a unique opportunity for in-depth observational studies, such as high-resolution imaging and radial velocity measurements, which could further elucidate the characteristics of substellar objects and their formation mechanisms.
Key implications of this discovery include the expanded census of the solar neighborhood and enhanced understanding of the local distribution of low-mass substellar objects. The identification of WISE 1049−5319 underscores the significance of WISE's contribution to brown dwarf searches, particularly through its ability to map proper motions over multiple epochs and its sensitivity to the infrared spectral bands, where brown dwarfs emit predominately.
The discovery is noteworthy for its potential influence on the strategies employed in current and future brown dwarf surveys. As noted, historical surveys may have been constrained by their avoidance of the galactic plane, where high stellar densities complicate the identification of high-proper-motion objects. The successful identification of WISE 1049−5319, located at a mere 5 degrees from the galactic plane, suggests that revisiting these dense regions with improved data and methodologies could yield further discoveries.
Looking forward, the characterization of WISE 1049−5319 provides valuable data for testing atmospheric and evolutionary models for brown dwarfs, especially concerning binaries with potentially diverse spectral types. Additionally, it presents a rare instance to study binary dynamics at a relatively close distance, potentially contributing to our understanding of orbital motions and interactions in substellar systems. The continued utilization of multi-epoch and multi-survey data will likely remain pivotal in uncovering additional members of our local stellar neighborhood and enhancing theoretical models of star formation and evolution in these unexplored sectors.