Evidence of a Mira-like tail and bow shock about the semi-regular variable V CVn from four decades of polarization measurements

Abstract

Polarization is a powerful tool for understanding stellar atmospheres and circumstellar environments. Mira and semi-regular variable stars have been observed for decades and some are known to be polarimetrically variable, however, the semi-regular variable V Canes Venatici displays an unusually large, unexplained amount of polarization. We present ten years of optical polarization observations obtained with the HPOL instrument, supplemented by published observations spanning a total interval of about forty years for V CVn. We find that V CVn shows large polarization variations ranging from 1 - 6%. We also find that for the past forty years the position angle measured for V CVn has been virtually constant suggesting a long-term, stable, asymmetric structure about the star. We suggest that this asymmetry is caused by the presence of a stellar wind bow shock and tail, consistent with the star's large space velocity.

arXiv comment8 pages, 5 figures, 1 table. Accepted for publication in A&A

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Cited by in corpus (4)

• Polarization simulations of stellar wind bow shock nebulae. I. The case of electron scattering
• Polarization simulations of stellar wind bow shock nebulae. II. The case of dust scattering
• The envelope of the semiregular variable V CVn
• A Multi-Year Photopolarimetric Study of the Semi-Regular Variable V CVn and Identification of Analogue Sources