$K_s$-band photometry of the Extreme T Subdwarf CWISE J221706.28$-$145437.6

TL;DR

This paper presents deep $K_s$-band imaging of the extreme T subdwarf CWISE J221706.28$-$145437.6, revealing its spectral energy distribution and unique absorption features, indicating it is cooler and more metal-poor than similar objects.

Contribution

First deep $K_s$-band photometry of this extreme T subdwarf, enabling detailed spectral analysis and comparison with benchmarks.

Findings

Exhibits exceptionally strong collision-induced absorption in $H$ and $K$ bands.

Likely cooler and more metal-poor than the nearest benchmark extreme T subdwarf.

Provides new insights into the properties of extreme T subdwarfs.

Abstract

We present deep $K_s$-band imaging of the extreme T subdwarf CWISE J221706.28$-$145437.6. Using the new photometry, we construct its spectral energy distribution and find this object exhibits exceptionally strong collision-induced absorption in the $H$ and $K$ bands. The comparison with the nearest benchmark extreme T subdwarf WISEA J181006.18$-$101000.5 suggests the object would be cooler and more metal-poor than the benchmark.