Evidence of V-band polarimetric separation of carbon stars at high Galactic latitude

TL;DR

This study presents the first V-band polarimetric measurements of CEMP stars, revealing a clear polarization-based classification linked to circumstellar dust asymmetries, which enhances understanding of their stellar evolution.

Contribution

It provides the first polarimetric data for CEMP stars, demonstrating a distinct polarization separation related to circumstellar dust geometry, a novel insight into their properties.

Findings

Stars with circumstellar dust show higher polarization.

Polarimetric separation correlates with dust distribution asymmetries.

Results suggest polarization can classify CEMP stars based on circumstellar environment.

Abstract

Polarization is an important indicator of stellar evolution, especially for stars evolving from red-giant stage to planetary nebulae. However, not much is known about the polarimetric properties of the carbon-enhanced metal-poor (CEMP) stars, although they have been well studied in terms of photometric as well as low- and high-resolution spectroscopy. We report here first-ever estimates of V-band polarimetry of a group of CEMP stars. V-band polarimetry was planned as the V-band is known to show maximum polarization among BVRI polarimetry for any scattering of light caused due to dust. Based on these estimates the program stars show a distinct classification into two: one with p% < 0.4 and the other with p% > 1. Stars with circumstellar material exhibit a certain amount of polarization that may be caused by scattering of starlight due to circumstellar dust distribution into non-spherically symmetric envelopes. The degree of polarization increases with asymmetries present in the geometry of the circumstellar dust distribution. Our results reflect upon these properties. While the sample size is relatively small, the polarimetric separation of the two groups (p% < 0.4 and p% > 1) is very distinct; this finding, therefore, opens up an avenue of exploration with regard to CEMP stars.