Discovery of an L4$\beta$ Candidate Member of Argus in the Planetary Mass Regime: WISE J231921.92+764544.4

TL;DR

We discovered a young L4β dwarf, WISE J231921.92+764544.4, likely a planetary-mass member of the Argus moving group, using infrared surveys and spectral analysis, with implications for understanding planetary-mass objects.

Contribution

This paper reports the identification of a new planetary-mass L dwarf candidate associated with the Argus group, combining survey data, spectral classification, and kinematic analysis.

Findings

Candidate member of Argus with 79% probability.

Estimated mass of 12.1 Jupiter masses, within planetary regime.

Spectral type L4β indicating youth and low gravity.

Abstract

We present the discovery of a young L dwarf, WISE J231921.92+764544.4, identified by comparing the Wide-field Infrared Survey Explorer (WISE) All-Sky Catalog to the Two Micron All Sky Survey (2MASS). A medium-resolution optical spectrum provides a spectral type of L4$\beta$, with a photometric distance estimate of 26.1$\pm$4.4 pc. The red WISE $W1-W2$ color provides additional evidence of youth, while the 2MASS $J-K_{\rm s}$ color does not. WISE J231921.92+764544.4 is a candidate member of the young moving group Argus, with the space motion and position of WISE J231921.92+764544.4 giving a probability of 79% membership in Argus and a probability of 21% as a field object, based on BANYAN II. WISE J231921.92+764544.4 has a mass of 12.1$\pm$0.4 M$_{\rm Jup}$ based on membership in Argus, within the planetary mass regime.