Mass loss rates inferred from mid-IR color excesses of LMC and SMC O stars

TL;DR

This study uses mid-infrared photometry to measure IR excesses in LMC and SMC O stars, revealing larger-than-expected mass loss rates and suggesting that stellar winds are highly clumped.

Contribution

It provides new IR-based measurements of mass loss rates in LMC and SMC O stars, challenging previous wind line analysis results.

Findings

IR excesses are larger than predicted by standard models

Mass loss rates are higher than previous estimates from wind line analyses

Stellar winds are likely highly structured or clumped

Abstract

We use a combination of VJHK and Spitzer} [3.6], [5.8] and [8.0] photometry, to determine IR excesses in a sample of LMC and SMC O stars. This sample is ideal for determining excesses because: 1) the distances to the stars, and hence their luminosities, are well-determined, and; 2) the very small line of sight reddenings minimize the uncertainties introduced by extinction corrections. We find IR excesses much larger than expected from Vink et al. (2001) mass loss rates. This is in contrast to previous wind line analyses for many of the LMC stars which suggest mass loss rates much less than the Vink et al. predictions. ogether, these results indicate that the winds of the LMC and SMC O stars are strongly structured (clumped).