HI envelope around the carbon star V420 Vul

Abstract

We report the detection of an extended 21-cm parsec-scale \ion{H}{i} structure toward the Mira variable V420\,Vul using archival Galactic Arecibo L-band Feed Array survey data. The emission exhibits a spatially coherent but intensity-asymmetric morphology that nevertheless retains a globally symmetric kinematic profile centered near $v_{\mathrm{LSR}} \sim 47.6\,\mathrm{km\,s^{-1}}$. At an adopted distance of $\sim 1.9$\,kpc, the structure extends over $\sim 20$\,pc, implying a dynamical timescale of order $10^6$\,yr. Although the total \ion{H}{i} mass ($\sim 70\,\mathrm{M_\sun}$) indicates that the atomic gas reservoir is heavily dominated by the ambient interstellar medium rather than pristine stellar ejecta, the spatially resolved spectra and position-velocity diagrams reveal an underlying symmetric velocity framework centered on the star. We interpret this as the dynamical imprint of the stellar wind preferentially channeling through a porous ambient cloud, demonstrating that cohesive kinematic records of late-stage stellar mass loss can be preserved over parsec scales and megayear timescales despite dominant interstellar coupling.