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arXiv · 2602.08756

An unusual pair of interstellar HI features and a related white dwarf star inside the HI cavity surrounding the Upper Sco-Cen OB2 Association

Gerrit L. Verschuur
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Abstract

Two mysterious unresolved HI structures at velocities of +12 and -6 km/s were discovered in high resolution 21-cm survey data in the direction of a faint white dwarf star. Examination of the HI morphology in this area of sky shows that the star and HI features exists in a large cavity in interstellar HI surrounding the Upper Sco-Cen OB2 Association. The cavity may have been created by an ancient supernova. It is hypothesized that the pair of HI features and filamentary HI structure found in its immediate vicinity may be the remnants of a planetary nebula some 3 x 10^5 years old that have cooled to the point that the gas is neutral and emitting the 21-cm spectral line. This remnant has maintained the morphological characteristics of the original planetary nebula because it expanded into a volume of space relatively devoid of interstellar gas that would otherwise have absorbed any traces of the original nebula.

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Gerrit L. Verschuur. 2026-02-09. An unusual pair of interstellar HI features and a related white dwarf star inside the HI cavity surrounding the Upper Sco-Cen OB2 Association. https://arxiv.org/abs/2602.08756

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