Do Hydrogen-deficient Carbon Stars have Winds?

TL;DR

This study investigates whether hydrogen-deficient carbon stars exhibit stellar winds by analyzing high-resolution spectra near the helium line, finding no evidence of winds in these stars, unlike in related R Coronae Borealis stars.

Contribution

It provides the first high-resolution spectral analysis of HdC stars near the helium line, showing they lack stellar winds despite chemical similarities to RCB stars.

Findings

No helium line evidence for winds in HdC stars

Wind lines in RCB stars are linked to dust formation

HdC stars do not produce dust, consistent with absence of winds

Abstract

We present high resolution spectra of the five known hydrogen-deficient carbon (HdC) stars in the vicinity of the 10830 Angstrom line of neutral helium. In R Coronae Borealis (RCB) stars the He I line is known to be strong and broad, often with a P Cygni profile, and must be formed in the powerful winds of those stars. RCB stars have similar chemical abundances as HdC stars and also share greatly enhanced 18O abundances with them, indicating a common origin for these two classes of stars, which has been suggested to be white dwarf mergers. A narrow He I absorption line may be present in the hotter HdC stars, but no line is seen in the cooler stars, and no evidence for a wind is found in any of them. The presence of wind lines in the RCB stars is strongly correlated with dust formation episodes so the absence of wind lines in the HdC stars, which do not make dust, is as expected.