2026AJ....171..192L

Ground-based observations around 1.4 μm are normally limited by strong absorption of telluric water-vapor. However, Dome A, Antarctica has exceptionally dry conditions that offer a unique opportunity for observations in this band. We designed a new filter covering 1.34-1.48 μm, namely ${W}^{{\prime} }$, and installed it on the Antarctic Infrared Binocular Telescope (AIRBT) at Dome A in 2025. AIRBT comprises two identical 15 cm optical tube assemblies and two InGaAs cameras equipped with J and ${W}^{{\prime} }$ filters, respectively. With this Early Data Release (EDR), we aim to evaluate the performance of the ${W}^{{\prime} }$ band at Dome A to observe objects with water-vapor features. This EDR covers ∼20 deg² in the Galactic plane using ∼20,000 images in three nights. For 2 s exposures, the 5 σ limiting magnitude histogram peaks at J ∼ 11.5 mag (Vega) and ${W}^{{\prime} }\sim 9.9$ mag, respectively. The $J-{W}^{{\prime} }$ versus J - H color-color diagram distinguishes ultracool candidates with water-vapor-absorption features from reddened early type stars. Furthermore, later-type stars tend to exhibit stronger water-vapor absorption. Some sources show larger ${\rm{\Delta }}{W}^{{\prime} }$ than ΔJ across the three nights, which we attribute to variations of their water-vapor-absorption depth. We conclude that it will be efficient to search for ultracool stars and estimate their spectral subtypes using ${W}^{{\prime} }$band imaging at Dome A, where the atmospheric transmission is high and stable.