2026ApJ..1000L...6Z

We present a stellar stream found in images of the nearby, nearly face-on, late-type galaxy, NGC 3938 obtained for the Large Binocular Telescope Imaging of Galactic Halos and Tidal Structures (LIGHTS) survey that is thin, has very low mean surface brightness (〈μ_g〉 ≈ 28.7 mag arcsec^–2 and 〈μ_r〉 ≈ 28.1 mag arcsec^–2), appears to lie nearly on the plane of the sky, and wraps more than halfway around a host galaxy that is otherwise apparently isolated. We estimate that the progenitor had a stellar mass of ∼3.7 × 10⁷M_⊙. Despite an intriguing apparent offset between the centroid of the host galaxy and the apparent center of the stream orbit, we find that we can reproduce the morphology, including this apparent off-centering, with simple models and standard assumptions about the host (thin disk centered within a canonical spherical dark matter halo) and the progenitor satellite orbit. We identify a number of detailed features of the stream, such as changes in curvature and density, that will require more complex models to reproduce. Even this rather simple system provides a rich set of constraints with which to explore the accretion history and gravitational potential of an otherwise unremarkable late-type galaxy. Given the depth of the LIGHTS images, this system is an example of the types of stellar stream that could be found in a majority of nearby giant galaxies with the 10 yr stack of Rubin/LSST data.