Evidence for Pulsation-Driven Mass Loss from delta Cephei

TL;DR

This study provides the first direct evidence that delta Cephei is losing mass through a pulsation-driven wind, revealed by infrared and radio observations showing a bow shock structure and quantifying the mass loss rate.

Contribution

It presents the first direct observational evidence of pulsation-driven mass loss in a Cepheid star, using multi-wavelength data to characterize the outflow and its origin.

Findings

Detection of a bow shock structure around delta Cephei.

Measured mass loss rate of approximately 1E-7 to 1E-6 solar masses per year.

Evidence suggests the wind is pulsation-driven rather than dust-driven.

Abstract

We found the first direct evidence that the Cepheid class namesake, delta Cephei, is currently losing mass. These observations are based on data obtained with the Spitzer Space Telescope in the infrared, and with the Very Large Array in the radio. We found that delta Cephei is associated with a vast circumstellar structure, reminiscent of a bow shock. This structure is created as the wind from the star interacts with the local interstellar medium. We measure an outflow velocity of ~35.5 km/s and a mass loss rate of ~1E-7 - 1E-6 Mo/yr. The very low dust content of the outflow suggests that the wind is possibly pulsation-driven, rather than dust-driven as common for other classes of evolved stars.