SIMP J2154-1055: A New Low-Gravity L4$\beta$ Brown Dwarf Candidate Member of the Argus Association

Abstract

We present SIMP J21543454-1055308, a new L4$\beta$ brown dwarf identified in the Sondage Infrarouge de Mouvement Propre (SIMP) survey that displays signs of low gravity in its near-infrared spectrum. Using the Bayesian Analysis for Nearby Young AssociatioNs II (BANYAN II), we show that it is a candidate member of the Argus association, albeit with a 21% probability that it is a contaminant from the field. Measurements of radial velocity and parallax will be needed to verify its membership. If it is a member of Argus (age 30-50 Myr), then this object would have a planetary mass of 10 $\pm$ 0.5 $M_{\mathrm{Jup}}$.

5 pages, 4 figures, accepted for publication in the ApJ Letters. Minor modifications to text and references

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• LACEwING: A New Moving Group Analysis Code
• Let the Great World Spin: Revealing the Stormy, Turbulent Nature of Young Giant Exoplanet Analogs with the Spitzer Space Telescope
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• A Brown Dwarf Census from the SIMP Survey
• A Census of the 32 Ori Association with Gaia
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• Spectral characterization of young LT dwarfs